Carrier ignition electrics

[Mike K]

Originally Posted by Big D

Thanks for the replies.



Mike - voltage at the battery when running at a fast idle is 7.2-7.4 volts so this seems right eh?


Cheers

Darryl

Yes, that sounds Ok.. But why isn't the 7.2 Volts getting to your resistor It should be there on the switch side of the resistor. Sounds like dirty-oxidised connections somewhere . You need to run it for a while to get an idea of what's going on - a short run from cold won't tell you much . This would be a good option

Mike

[Lynn Eades]

Some of the wire used to rewire your carrier is too light for a six volt system. (blue at resistor goes to a skinny white) It's might be fine for a twelve volt system.
The cross sectional area of the wire looks too small.
If you apply six volts to that resistor , you should get 4.2 out the other end.
If you have a high resistance (voltage drop) before the resistor ( in a switch, or corroded terminal etc)under load it will drop your input voltage.
Hook your resistor up direct from a battery, through a test light or bulb, and then apply your volt meter, to check your output voltage. Then you know its not your resistor.
Note. The voltage in your primary ignition circuit varies depending on points being open(0 volts) or closedResistance of coil), changes when cranking, and again when running.

[Big D]

Hi Lynn,

Yes, you are right. The wire to the coil is very fine in comparison. What I will do is run a jumper using decent sized cable, in parallel with the existing wire from the resistor to the coil, and measure it again. That will be a good test to see if that is where the voltage drop off is.

Cheers

Darryl

[Mike K]

Originally Posted by Big D

Hi Lynn,

Yes, you are right. The wire to the coil is very fine in comparison. What I will do is run a jumper using decent sized cable, in parallel with the existing wire from the resistor to the coil, and measure it again. That will be a good test to see if that is where the voltage drop off is.

Cheers

Darryl

The coil is drawing about 4 amps from memory.. not really enough to be worried about thin wires .. The main wires to & from the battery - reg. and ammeter and lights need to be heavy though . I would be checking the ignition switch and the connections on it... put your voltmeter on either side of the IG switch .

[Bob Moseley (RIP)]

Hi Darryl - this probably won't help you much, but by way of comparison here are two images of my latest aquisition. Whowever removed this fro the Carrier was very carefull by retaining all the original wiring.

Bob

[Big D]

Thanks all for the replies and also the pictures Bob.

I haven't yet got to the bottom of this but have had a bit of fun playing around with the problem.

I've gone over all the connections, cleaned up any that looked marginal but basically found nothing untoward.

I managed to source two secondhand ignition resistors as well as getting a new resistor from Ajays. Interestingly, when fitted they all gave slightly different voltages at the coil. The highest voltage I got was 2.95 volts though with the new resistor. The voltage at the 'hot' side of the resistor is still 6.4 volts with a fully charged battery.

In the end I did a little trick with the ignition resistors and hooked up two of them in parallel (my old electronics days coming back!) to halve the resistance. This results in a voltage to the coil of about 3.4 volts.

By disconnecting the existing coil wire and using heavier gauge wire looped between the instrument panel and the coil, I found I got about an extra 0.2 volts at the coil. I haven't decided yet whether that is sufficient to make me want to try to attempt to feed through that new piece of wire through all the conduit and cable coverings. That could be a mission!

I guess there could be an 'issue' with the coil itself and its internal resistance which is accounting for the lower voltage on it.

The carrier is starting sweetly though and hasn't ever missed starting first time (apart from when I ran it out of gas the other day). While I'm not ready to wave the white flag, I'm almost inclined at the moment to leave well enough alone.


Cheers

Darryl