The Snakes Alive CMP Wiring Project

[Phil Waterman]

Originally Posted by Grant Bowker

Agreed that the page in MB-C doesn't seem to show the markers going through the junction block but that doesn't make much sense to only make it easy to disconnect part of the wiring.


A reliable source shows a photo of an unmolested wiring harness removed from a known original vehicle and clearly shows wires in the main harness of the same (+/- a tiny bit) length to connect headlights and markers, all through the junction blocks. http://canadianmilitarypattern.com/R...arness%203.JPG

Hi

Thanks Grant, I was in the process of digging out the same photo, that is the wiring from my 1945 HUP, I'll now try to find the photo of the 1942 C60S wiring harness.

But I suspect the difference is just evolution of CMPs they did make ongoing production changes in responses to reports back up through the maintenance channels. The logic I see to all the nose lights all coming to the same terminal blocks is it really annoying when you are pulling the nose off a CMP is to find you just ripped out a wire. It takes me 20 minutes to take the nose off Pattern 13 Cab which makes it a lot easier work on the engine. If you had to chase around and find all the connections it would take longer.

Cheers Phil

[Jacques Reed]

Good Day,

I’ve decided to re-do my 25 year old wiring harnesses on my F15-A.

A number of reasons:
Basically back in the mid-nineties I copied non-original harnesses that were on my first truck. At that time I did not even have a Repair Manual for a wiring diagram so I copied the colours and wire gauges as best as I could estimate from the existing harnesses. A bad call in hindsight.

Interestingly, those harnesses I copied used plastic covered wires but they were in original looking woven cotton shrouds. I am surprised they weren’t cotton braid covered wires, but perhaps someone went to a lot of trouble to run wires through the original shrouds even if wrong colours were used.

Another consideration was adding turn signal wires. I know it isn’t original but I believe it is essential in modern traffic to have them. The wires are less obvious inside the new original style harnesses. I made them slightly longer to differentiate them from the original wiring and give a bit more clearance at the solenoid.

I also wanted to add the Autopulse wire to the harnesses. Although not used on Australian vehicles it could come in handy to add an electric fuel pump, if required, at a later date. The wire was fitted originally even if not used but I left it off my first version.

I had hoped to use cotton braid covered wire but I opted for modern automotive wire instead. In reality, very little of the wire is visible so I couldn’t justify the high cost of a commercially made harness. I would not be able to reproduce the woven cotton shrouds anyway so it made even more sense to go with modern wire. I used vintage style bitumen impregnated conduit for the shrouds instead which, although not original, looks in keeping with the era of the truck. I spent about $175 for all the materials.

I obtained a rough, but complete, main harness a while back and a NOS horn (lower chassis) harness for patterns. Over time, I have measured all the lengths of wire and tabulated what I needed in colours and wire gauge.
I used Tycab Australian made automotive wire throughout. I tried to use trace wires wherever possible to identify the wires similar to the original colour coding. In some cases the wire/trace colour combinations were just not available however. In those cases I added a length of heat shrink tubing of the appropriate trace colour to identify it.

I made one exception to the original colour codes. I made the horn wire from the solenoid orange/green band to avoid confusion with the left fuel sender. Both are normally yellow/green x 2. Only a few inches of the horn wire at the solenoid is visible so I can live with that.

So the instrument panel is done, the horn harness is done, so just the main harness to finish off. All wires for it have been cut and run so a just bit of soldering to finish it off.

Hope this is of some interest.

[Jordan Baker]

Very nice work.

[Jacques Reed]

Good Day,

Thought this may be of interest. Found these yesterday in a junk shop in Melbourne. NOS 6V Ford script headlight globes.

Interestingly they say "Made in Holland" on the base.

I guess it is safe to assume that they were made post war! Part No. indicates a 1941 design. Must have made them for only a short time afterwards as sealed beams were in common usage by then.

You just never know what will turn up 70 years later.

Just noticed in Parts list * C01Q 13009 Bulb 32-21 C.P. 6-8 Volts is lower candle power on High than these at 50 C.P. on High. Better illumination with these ones but draws more current.

Cheers,

[m606paz]

Can help me with this Ford wire no listed in part list?

[Andrew Rowe]

Part number would almost suggest that this is for a Rear - engine armored car,
For the Indian Pattern one's, armored cable, Cheers Andrew.

[Jacques Reed]

Some aspects of the following may have been covered before on MLU but it may still be of interest to restorers.

I have noticed most wiring diagrams in Ford CMP Maintenance Manuals and Handbooks do not show the wiring for an ammeter equipped instrument panel. A discussion about wiring with a fellow MLU Member prompted me to investigate it a bit further. The only reference I could find was a 1945 Australian “Drivers Handbook for Ford” which showed an “Ammeter” in the dashboard layout diagram. All other publications show it as a “Battery Indicator” There are also some wartime Ford commercial truck wiring diagrams showing an ammeter and not a battery indicator.

Thanks to Mariano Paz’s 1945 Ford CMP wiring diagram data plate, my original harness, and the link below I have a clearer picture. Also going back to Electricity 101- Ammeters vs Voltmeters helps to make it clearer. Ammeters- measure current flow in a circuit and placed in series. Voltmeters- measure electrical potential difference between two points in a circuit and placed in parallel.

1939-40 Fords, Mercs, and Lincolns, and early war CMP’s used a gauge with “BATT” displayed on the face which is really a voltmeter. Ammeters display “DIS-CHG” on the face. Later in the war, the Ford commercial instruments, used in the CMP’s, were changed from battery indicators to ammeters. This was prior to the military round gauge instrument panel being adopted. As of the May 1943 F15-A Spare Parts List. however, only “Battery Indicators” are listed, and not ammeters.

On indicators with “BATT” displayed the current flows from the starter solenoid first to the voltage regulator battery terminal, then to the ignition switch, and then to one terminal on the Battery Indicator. The other terminal on the indicator goes to earth. This is shown on all the early wiring diagrams and is correct. I must admit I thought in the past that was wrong but I was looking at my ammeter’s wiring and not that of a voltmeter.

When the Ford commercial ammeters replaced the battery indicators on CMP’s the wiring could be the same for both the Ford gauges and the military round gauges. The current flows from the starter solenoid to the ammeter first, and then to the voltage regulator battery terminal. If an early BATT gauge harness is used on an ammeter equipped truck or an ammeter harness used with a battery indicator equipped truck it could cause serious electrical problems.

Things to keep in mind if repairing, making or buying a wiring harness, or changing gauges.

And yes, the battery indicator and oil pressure gauges are on the wrong side in the photo and “BATT” should be on the bottom. That’s how I bought it.
I have been told the gauges are the same and can be used if you change the faces, but you can only swap a BATT, not an ammeter, with the fuel gauge, and the temp with the oil pressure gauges due to the mounting hole positions.

Hope this is of some help and interest.

The following link may help to explain it all.

https://fifthaveinternetgarage.blogs...gauge-and.html

[Ganmain Tony]

Following Jacques excellent information, found this diagram in the drivers book.

Ford Special Pattern Vehicles Third edition, Page 184.

[Jacques Reed]

Good Day,

A while back I noticed a short 22" long wire attached to the left side of the small harness on the Ford cab 13 shell. It lead nowhere and had been cut, but tracing it back it went to the sidelights terminal on the terminal block. On that basis it was most likely the original lead to the left sidelight. It reached all the way to the left sidelight and when moved to the tail at the terminal block for the right sidelight, it would also reach the right sidelight.

Looking at the parts list, the sidelight assembly is a different part number to the tall and stop light assemblies. It could be the different lenses fitted and it could also be the different lengths on the leads. The tail and stop light leads are much shorter.

If a short tail/stop light fitting is used as a sidelight it would require a short wire with bullets both end to connect to the shell harness. I doubt if Ford would waste the extra resources to accomplish this so I am 99% certain that the sidelights had longer tails. I made mine 24" long just to be on the safe side and they connect up perfectly.

Just some more good intel from my $400 parts truck.

Hope this is of some interest.

[Tony Smith]

Originally Posted by Jacques Reed

Ammeters- measure current flow in a circuit and placed in series. Voltmeters- measure electrical potential difference between two points in a circuit and placed in parallel.

Later in the war, the Ford commercial instruments, used in the CMP’s, were changed from battery indicators to Ammeters. This was prior to the military round gauge instrument panel being adopted. As of the May 1943 F15-A Spare Parts List. however, only “Battery Indicators” are listed, and not ammeters.

When the Ford commercial ammeters replaced the battery indicators on CMP’s the wiring could be the same for both the Ford gauges and the military round gauges. The current flows from the starter solenoid to the ammeter first, and then to the voltage regulator battery terminal.

Hope this is of some help and interest.

Don't know why I didn't pick up on this at the time.

The Ford Commercial Amp Gauge IS NOT wired in series. The gauge uses an inductive coil to measure the current flow (and direction). Look at the back of the gauge. There are no terminals, but there is a steel "bridge" device. The wire from the "Batt" terminal on the voltage regulator (itself in turn connected to the neg terminal on the battery) to the Starter solenoid is an 8ga wire and PASSES THROUGH this bridge. The current flowing through the wire creates an electromagnetic field, the strength of which is read in the inductive coil, and deflects the needle on the gauge.

The later round "Military" Amp gauge does have terminals on the back of the gauge and IS wired in series, and the wire from the Voltage regulator is in two lengths with terminal ends that connect to each terminal on the back of the gauge.

So the wiring harnesses for "Ammeter+Commercial instruments" and "Ammeter+Military Instruments" are different. If you have the early "Inductive" style harness, it is a simple matter of cutting the VR to Starter wire and adding terminal ends to suit the Mil gauge. If you have the later "Series" harness, you need to replace the VR to Starter wire with a single length of 8ga wire.

The Inductive Amp gauge was probably superceded for reasons other than just the availability of round military gauges. The Inductive coil gives a good "Indication" of charge/discharge, but is not terribly accurate for the actual current amperage value compared to a gauge being wired in series. In addition, the unsecured wire passing through the bridge is prone to chafing and shorting out, particularly on a military vehicle which might be expected to see some rough roads and a lot of shaking. Worst case is a vehicle fire, best case scenario is a shorting out of the electrical system and a "Fail to Proceed".

[Jacques Reed]

Tony,

It appears there are two types of Ford ammeters used on the Ford CMPs then.
I took my information from the original harness after tracing out the wires. That round gauge ammeter has two terminals and is wired in series to the voltage regulator from the battery.

Second photo is the back of a NOS Ford Ammeter also with two terminals. The lower left gauge. The face of it is shown in a previous post and has the same face as the one you show.

Added a 1941-42 Truck wiring diagram showing the ammeter in series.

[Lynn Eades]

I'm not sure of the significance, but in Australian carriers, If they were fitted with the battery gauge (volt meter), then they usually had a three brush generator. If they had an amp meter, they were usually fitted with the two brush generator. Hopefully I have this the right way around, without looking in a book.
Thanks on the Auction heads up Tony.

[Hanno Spoelstra]

Originally Posted by Jacques Reed

It appears there are two types of Ford ammeters used on the Ford CMPs then.
I took my information from the original harness after tracing out the wires. That round gauge ammeter has two terminals and is wired in series to the voltage regulator from the battery.

Second photo is the back of a NOS Ford Ammeter also with two terminals. The lower left gauge. The face of it is shown in a previous post and has the same face as the one you show.

Added a 1941-42 Truck wiring diagram showing the ammeter in series.

Here’s a photo of my spare instrument cluster. It has an Ampere meter but it is wired separately from the oil pressure meter - there is no bridge.

Now I need to study the various wiring diagrams to see if it can be wired in in my 1943 F15A which has the BATT meter (last photo).

[Bob Carriere]

Hanno... Jacques...bonjour!!

.....even lowly Chevrolet have a Amp meter.....but really does not tell you much except your system is charging....or an even keel or running on the battery and discharging.......

Neat idea with the solid brass bridge as it must eliminate a whole bunch of wires.

On the Chev, along with the builtin bypass, all my power wiring has to be first connected to the Amp meter which makes for a very cumbersome nest of wires on one bolt connection....... which forever needs tightening!!!....my dash lights are not working now...guess why???

A volt meter, or engine oil temperature gauge, and vacuum gauge would be much more useful......

[Jacques Reed]

Hi Hanno,

Just had a look again at the back of the Ford Cluster. I think the brass bridge between the ammeter and the Oil pressure gauge should not be there. That is used with a battery indicator type gauge to supply power to all the gauges when the ignition switch is thrown.

Will have a look at the wiring again later today and make up a revised Ammeter equipped wiring diagram at the instrument panel using Mariano Paz's great information on the late war wiring plate.

Cheers,

[Jacques Reed]

Hi Hanno,

Here is a revised wiring diagram showing the differences in red between a Battery indicator gauge equipped instrument cluster and an ammeter equipped one.

Not a lot required to change over to an ammeter from what I can see. Mainly the routing of the supply from the solenoid to the Battery terminal on the regulator.

Original Regulator Battery terminal to Ignition switch wire can stay even though Mariano's diagram takes current from the Ammeter to the Ignition switch. Same thing electrically however.

Only one Brass bus strip used, too, from Fuel to Temp gauges. If ammeter to Oil pressure gauges had a bus strip all gauges would be "Hot" all the time. They should be only be energised when Ignition switch is thrown.

Thanks again to Mariano Paz's excellent late war wiring plate photos. Makes it so easy to trace wires compared to the rudimentary Ford Manual schematics.

Fairly happy with it all but always glad for "peer review" as they say. It can be easy to miss things.

Cheers,

[Hanno Spoelstra]

Originally Posted by Jacques Reed

Just had a look again at the back of the Ford Cluster. I think the brass bridge between the ammeter and the Oil pressure gauge should not be there. That is used with a battery indicator type gauge to supply power to all the gauges when the ignition switch is thrown.

Thanks Jacques. I've always thought that my BATT meter did not do much, I now found it has a live feed (bridged to the oil pressure gauge), but no wire to ground - see photo. This makes me wonder why it was moving at all? Will add a ground wire and see how it behaves.



PS: the white terminal block will be removed. I noted this loose yellow & red wire dangling under the dash and it turned out to be live. Using the diagrams on here I found this is the feed to the inspection lamp socket. This socket was removed in the past to make way for a traffic indicator switch.

Will have a look at the wiring again later today and make up a revised Ammeter equipped wiring diagram at the instrument panel using Mariano Paz's great information on the late war wiring plate.

Will look at that in detail later. I am trying to get a better understanding of my F15A's wiring, making it work better and meanwhile draft the specs for the new loom I want to order.

I may switch from the BATT to AMP meter, though I plan to use an electronic regulator. I've just replaced the indicator/ flasher relay by an electronic one, and it is a huge improvement because it uses far less power and it is independent of load. I am becoming a fan of modern electronics. I recently fitted an electronic distributor, quite an improvement so I plan to add more in an effort to improve drivability and reliability.

[Jacques Reed]

Hi Hanno,

Just looking at your picture there should be a wire, 30A, a jump from the oil pressure gauge brass bus to the Temperature gauge brass bus to supply current to the Battery and Oil Pressure gauges when the ignition switch is thrown.
There should be wire, 30, from the ignition switch to the Temperature gauge brass bus to supply current to the Temperature and Fuel gauges and then to the other gauges via 30A.

The wire into the Battery indicator is my concern. If it shows voltage only when the ignition switch is thrown then it is wire 30 and can be connected to the brass bus at any gauge to supply them with current. Diagram shows the Temp gauge but any brass bus is the same electrically.

If for some reason that wire into the Battery indicator shows voltage continuously it could be coming directly from the Battery via the regulator and therefore your wiring is setup for an ammeter. If that is the case it could cause a serious problem to the wiring and gauges if the Battery indicator is sent to earth. A quick check will determine if that wire is "hot" only when the ignition switch is on and therefore set up for a Battery indicator.

I have found with numerous owners over the years and many jury rigged wires on these vehicles it is best to check and double check. My first truck had many disconnected wires and even house wiring used in some places!

Cheers

[Hanno Spoelstra]

Originally Posted by Jacques Reed

Just looking at your picture there should be a wire, 30A, a jump from the oil pressure gauge brass bus to the Temperature gauge brass bus to supply current to the Battery and Oil Pressure gauges when the ignition switch is thrown.
There should be wire, 30, from the ignition switch to the Temperature gauge brass bus to supply current to the Temperature and Fuel gauges and then to the other gauges via 30A.

The wire into the Battery indicator is my concern. If it shows voltage only when the ignition switch is thrown then it is wire 30 and can be connected to the brass bus at any gauge to supply them with current. Diagram shows the Temp gauge but any brass bus is the same electrically.

If for some reason that wire into the Battery indicator shows voltage continuously it could be coming directly from the Battery via the regulator and therefore your wiring is setup for an ammeter. If that is the case it could cause a serious problem to the wiring and gauges if the Battery indicator is sent to earth. A quick check will determine if that wire is "hot" only when the ignition switch is on and therefore set up for a Battery indicator.

I have found with numerous owners over the years and many jury rigged wires on these vehicles it is best to check and double check. My first truck had many disconnected wires and even house wiring used in some places!

Hello Jacques, thanks for your guidance.

Currently the dash on my F15A is wired as follows:

• Live feed from ignition switch to BATT, strip connector to OIL pressure, then a wire runs (hence the double wire in the connector) from BATT to TEMP with a strip connector to FUEL.

I checked and the instruments are "hot" only when the ignition switch is in the on position. I have temporarily grounded the BATT meter (see the blue connector) and when the engine is running it slowly creeps up. Have yet to take it for a test drive to see if it is in the green at driving speeds.



Indeed previous owners have fiddled with the wiring, hence my actions now to go through it, understand and correct it. It does not help the original covering has faded to a level where the colours are very hard to discern. Hence a rewire is scheduled for this winter.

For the upcoming event this weekend I have proper working indicators again, over the years they became dimmer and dimmer, with the old mechanical flasher relay, dash indicator light and bad connections robbing away 1.5 V from the 6 V available. With the connections cleaned up, dash indicator light omitted and an electronic flasher relay I now have the full 6 V supply to the indicator lights.

[Ganmain Tony]

Where is the other end of your battery gauge ground wire connected Hanno?

[Hanno Spoelstra]

Originally Posted by Ganmain Tony

Where is the other end of your battery gauge ground wire connected Hanno?

Tony, my F15A has a ground stud under the dash, just above the steering column. That’s where I’ve grounded the flasher relay and the BATT gauge.

[Ganmain Tony]

Thanks Hanno.
I will probably do something similar so it's good to see what other set ups look like.
Great to see your truck, nice example of an F15A.

[m606paz]

NOS wiring to install on my FGT. C39Q 14401 B. Thirth lamp socket for HI Bean indicator....

[Jacques Reed]

A recent discussion on another forum about the use of Radio Suppression condensers (capacitors) on the fuel senders got me thinking about the design of the fuel sender unit on a Ford.

It was suggested that the condensers served another purpose which was to reduce arcing at the contacts inside the sender as it made and broke contact in operation. This is similar to the use of a condenser at the ignition points. This could be desirable on a device fitted close to fuel vapor; however, I think this was not necessary and the designers, (King Seeley?) didn’t consider it as an issue with a well-sealed unit.

Interestingly the condensers were only fitted “as required”, and not a standard fitment to all CMP vehicles which implies the senders were designed so that any arcing at the bimetal contact is satisfactorily shielded from petrol fumes or liquid. There is also the hot heating wire for the bimetal arm to consider.

I thought I would open up a unit for a close inspection. I had one which I had condemned for a hole eaten through the casing. I made sure there is no liquid inside it by shaking it vigorously as I would be using a Dremel cut off wheel to open it up. Even 50-year-old petrol is flammable.

As the photo shows it has some identifiable parts from the operating diagram. Virtually everything inside attached to the bimetal arm is insulated from earth. There is an adjustment cam for factory setting the starting contact point on the bimetal arm. This cam is insulated from the bimetal arm by what looks like a Bakelite pin. The movable arm on the bellows is earthed as is all the sender casing.

The unit is sealed with a substantial rubber gasket. As far as fumes leaking into the sender, this could only occur if the bellows had a hole in it, or the tank side of the sender had a hole (my condemned one) or there was a hole in the outside of the sender unit and fumes got in, such as in a during refuelling. Ignition should be switched off in any case during refuelling.

So, I think there is a low chance of a fire caused by a sender as long as it is good condition and not suffering from corrosion, or damaged in a way that the internals are exposed to vapor. Having said that, I would have a good check of any fuel sender unit for signs of holes or damage before putting it into service.

Will be interested to hear other comments on this.

Hope this is of some interest.

[m606paz]

The Ford Solenoid are ground activated, ok?
But modern replacement solenoid no says are ground or voltage activated... how buy?

[Jacques Reed]

Hi Mariano,

The direction of the magnetic field in a solenoid is determined by the current flow in it. if you swap the positive and negative terminals in a solenoid the direction of the magnetic field changes direction 180 degrees.

So, if a positive earthed solenoid (early Ford) was replaced with a negative earthed (later) one the magnetic field, and thus the force, on the armature, the centre part that closes the contacts between the battery and the starter, would be reversed.
This would cause the force on the armature to be away from the contacts and thus no closing of them to supply current to the starter would occur.

Search "Right hand Rule for Solenoids" for more info.

Also, as current flow by convention is positive to negative, perhaps "voltage activated" refers to a positive voltage applied to the solenoid in a negatively earthed one.

Hope this helps.

Cheers,

[m606paz]

Hi Jacques, thanks for your reply.
I say voltage activated according this diagram for Tractors

[Jacques Reed]

Hi Mariano,

I just put my multimeter on two old Ford starter solenoids. There was no continuity between the cases and the starter button terminals which indicates to me they are ground activated.

I also checked the continuity between the battery terminal (negative) on the solenoid and the starter button terminal and there was continuity there. This is the same at shown in the ground activated diagram.

There is no voltage at the start button. Only when it is pushed (earthed) does current flow from it, (positive) to the battery side of the solenoid, (negative)

Cheers,

[m606paz]

Hi Jaques
Thanks for the explanation, it has been very useful and a learning class for me.

So....
It's getting hard to get the right solenoid to work with the positive ground. All the ones I get here are postwar with negative ground.
Now, on the late electrical circuit data plate, it indicates that vehicles destined for India were negative grounded. What changes do I have to make to make it work with Negative Ground? Is it only to change the polarity of the battery and the instruments and electrical elements do not need changes? Only the solenoid is changed according to...?

Regards

[Mike K]

Originally Posted by m606paz

Hi Jaques
Thanks for the explanation, it has been very useful and a learning class for me.

So....
It's getting hard to get the right solenoid to work with the positive ground. All the ones I get here are postwar with negative ground.
Now, on the late electrical circuit data plate, it indicates that vehicles destined for India were negative grounded. What changes do I have to make to make it work with Negative Ground? Is it only to change the polarity of the battery and the instruments and electrical elements do not need changes? Only the solenoid is changed according to...?

Regards

Hi Mariano

The generator polarity needs to be changed if you are changing the battery terminals over.

The field coils in the generator are wound around iron cores, the cores have a small amount of residual magnetism in them that controls the polarity of the coils. It is easy to change the residual magnetism by quickly connecting a battery through the coils, it only takes a fraction of a second , the iron cores re-establish themselves with the opposite polarity .