Temperature gauge question

[Tom Millward]

Hello fellow Carrier owners and knowledgeable persons,

I had my Carrier out on Salisbury Plain a few weeks ago, driving the many graded range roads and a bit of cross country.. I’m starting to use it more and so I need to fix my faulty temperature gauge. When switched off it reads maximum temperature. When switched on it moves to the mid range temperature and once the engine is running very quickly moves back to maximum again. Hence I don’t have a true reading of the engine temperature.

Can these gauges be repaired? Does anyone know if a modern replace that can be fitted as a stop gap? Or even better does anyone have a spare they’re willing to part with?

My Carrier is running on 12v, I’ve replaced the voltage converter thinking that might be the cause, but it made no difference. Could the senders be at fault? (I hope not as they’re about £75 each here in the UK!).

I have a road run coming up and I’d like to be able to monitor the engine temperature. It seems roasting hot after a decent stretch of road running, but without a working temperature gauge it’s impossible to tell!

Cheers,

Tom

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[Tony Smith]

This thread http://www.mapleleafup.net/forums/sh...ad.php?t=28237 explains the operation of the Ford temp sender and gauge in the standard 6v system, and notes the different system in 12v setups. Perhaps your 12v conversion has used different components and resulted in a dysfunctional circuit?

The gauge operates by voltage heating a bi-metal conductor which deflects the needle. This should not be polarity dependant in a Positive or Negative earth change.

[Tom Millward]

Thanks Tony, I’ll have a good read of those posts and try and figure out where my circuit is going wrong.

[Phil Waterman]

Hi

Have not played with it yet but would switching polarity, this is based on the Amp meter if the polarity reverse the needle moves the wrong direction.

Cheers Phil

[Bruce Parker (RIP)]

Tom, if it's a Canadian UC then your gauge is doing exactly what it's supposed to do. Ignition off, with no current going to it, it reads all the way to the right (ie. max). Switch the ignition switch on and the needle, now with current, goes all the way to the left (ie. cold, assuming the engine is cold). As the engine runs it shows the temperature of the engine. I expect if your gauge is reading hot after a good run hill and dale it's because the engine really is hot.

[Tom Millward]

Hi Bruce, my gauge is doing as you say when the ignition is off, but when I switch it on with a cold engine it only goes halfway down the gauge, and reads normal operating temperature (engine is cold). Hence when it starts to warm up (not fully warm) the gauge goes to the right and reads off the scale.

[Tom Millward]

Originally Posted by Phil Waterman

Hi

Have not played with it yet but would switching polarity, this is based on the Amp meter if the polarity reverse the needle moves the wrong direction.

Cheers Phil

Hi Phil, I’ve not tried switching polarity yet, I’ll try that as well.

[Tony Smith]

Polarity makes no difference.

The gauge works by current flowing though a wire winding around a bi-metal strip. As the winding heats the strip, it bends, deflecting the needle on the gauge. The current flow, and the frequency of the circuit opening is dependant on the temperature of the sender on the Cyl Head.

For the gauge to correctly indicate, it needs the correct voltage and amperage flowing through the wire to cause the strip to heat at a certain rate, but polarity doesn't change the heating of the bi-metal strip.

The gauge operates with MORE current showing a COLDER indication, and LESS current showing a HOTTER indication. A full 6v across the gauge should move the needle fully to cold.

Tom, I'd be putting a Multimeter on the back of the gauge with the Ignition on + engine cold, and then again as the engine is running at operating temp (and showing off the scale).

To me, it seems like you are putting less than 6v through the gauge. This could be caused by the 12v reducer not giving you a full 6v at the gauge, or defective wiring with too high a resistance, or a poor ground (either at the Instruments, or engine to hull).

There is also the chance that the gauge or sender are defective, but as they seem to be showing some of the right functions, I would say they are working OK if given the correct diet of electrons.