Carrier ignition electrics

[Big D]

Gidday all,

I have another wee issue with the carrier I recently bought. I’m not sure whether I am confused about how the ignition system should actually work and be set up, or whether something isn’t quite right.

I’ve noted that it was a bit of a hard starter since I had it. I put it down to the technique I was using and perhaps also the change in location. The previous owners always found it a good reliable starter.

One thing I did notice was that when it was stubborn in starting, the spark at the plug seemed really weak, almost as if there was a kill switch somewhere. By chance I found if I turned on the inspection lamp switch, the carrier would often start (dependent on whether I’d flooded it or not I think). Once it was running though, if I turned off the inspection lamp switch, it would make the engine stall.

From what I remember, turning this switch on wasn’t part of the startup procedure when I first looked at the carrier, but I’ve sent the previous owners a message to confirm this.

I did some more checking on the electrics. The coil appears to be an original type Ford 4.2 volt coil. I got my voltmeter out and found that with just the ignition switch on, the voltage at the coil was 1.97 volts. When I switched the inspection lamp switch on, the voltage rises to 4.2 volts at the coil.

I pulled out the control panel for a closer look and I’ve attached a photograph which might hopefully show the wiring a bit better.

The white wire on the ignition resistor is coming from the ignition switch. The blue wire from the resistor goes to the coil.

I’ve noted that there is a connecting wire (the thin red wire in the picture) running from the coil side of the ignition resistor to the inspection lamp switch (the non-live side). The other side of the inspection lamp switch is a ‘live’ line coming from the fuse box.

When the inspection lamp switch is turned on, this effectively puts 6 volts to the coil side of the ignition resistor.

I can’t find a reference to the ignition resistor in the spare parts manual but this one measures 2 ohms. Presumably if that 6 volts is going to the coil when the inspection lamp switch is turned on, it is still being 'stepped-down' somewhere before it hits the coil?

Have I missed something here? Should the inspection lamp switch be part of the ignition system?

Was this setup just part of a cunning move by the previous owner when he did the ignition?

Is there any reason why there would be a feed between the inspection lamp switch and the ignition resistor?

I guess I could just leave it as is and have the inspection lamp switch on all the time, but I'd like to know I have things right.

Any thoughts would be appreciated.

Thanks.

Cheers

Darryl

[cletrac (RIP)]

That looks like a resistor for a 12 volt system. Personally, I've never seen a resistor used on a 6 volt system.

[Pedr]

It is critical with 6 volt system running original Ford coils that there is an ignition resistor in circuit, as the original coils are 4.2 VOLTS, failure to install one or maintain it as servicable will ensure that the coil will overheat and leak, ergo...dead coil.

Daryl, am currently at work and don't have manuals on hand, will check tonight the status of the wiring to the inspection lamp point. The previous owner may, as you have suggested created a hotwire system utilizing the switch, but other than that, I can see no reason for that switch to be in circuit. However is it "constant live", that is to say, doesn't require the ignition to be live to use the lamp. ( this is merely speculation on my part, without suitable documentation to support the theory )

Perhaps one of my learned brethren could offer some pearls of wisdom....Tony?, Rick? Others

Regards,

Pedr

[Big D]

Gidday folks,

Thanks for the replies.

cletrac - yes, I am not familiar with the resistors at all so couldn't say for sure whether this is the right type. The voltage does appear to be stepped down correctly but it is how it is being done that has me curious.

Pedr - I have looked over the circuit diagram in the workshop manual and I don't see any link as such between the inspection lamp and the resistor. I will check the voltage across the inspection lamp switch with the igntion off and see what that is. That might help to narrow down what is going on. I'd be interested in what you thought though after looking at the circuit diagram.

Cheers.
Darryl

[Mike K]

Hi Darryl

That looks like one of my wiring jobs .

As Pedr said .. you do need a resistor with those 4 volt coils .. the system was prone to faults as Ford thermselves woke up changed it to a seperate coil setup.

The divers bell coil will gain some radiant heat from the motor block and radiator , stuck down there .. not a good idea.

The value of that resistor is critical ... the wire in the resistor has to be special wire .. like the wire used in electric heating elements, its made with tungsten or something. You can make up your own resistor by unwinding the element from an old electric heater, but you cannot solder it.

I agree with David, that resistor looks like a 12V off the shelf one .. its value will be too high. A good idea is: you can buy another resisitor of the same type and solder it across that one( parallel), that will half the total ohms and double your voltage at the coil, and double the wattage rating too. . You want the resistor to be stable..not change its ohms value with heat , which is what ordinary wire does.

Mike

[Lynn Eades]

It seems to me the resistor is wrong, and when you turn on your light, the power is going via the circuit to your coil. The bulb is acting as the resistance in your circuit, which just so happens to give 4.2 volts to the coil.

[Rob Beale]

is wound as a small coil about 1 inch long and 3/16 inch dia. It acts as an inductor to stop the current to the coil collapsing when the heavy load of the starter is engaged.

reading the other posts, leads me to believe the extra wire is to provide an alternative current path, as Lynn describes. ie It seems to be taking current FROM the switch TO the coil side of the resistor.

If all else fails, I would disconnect all accessories and leave the ignition, charging and starting circuits intact, then check through them as you have been doing.

Ajays in Katikati may be able to supply the correct 6V resistor

best luck
Rob

[greg anderson (RIP)]

When I wired my carrier I bought an after market resistor which was to have been the correct replacement and it did not work well -I put the old one back in and my carrier starts well (touch wood) -nuff said -Greg

[Big D]

Thanks for the replies.

I checked things again with a second voltmeter just to be sure. This showed 2.8 volts at the coil when the ignition is switched on and 1.6 volts when the engine actually starts.

I've found now though that the engine starts instantly first time even when stone cold.

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

Ajays in Katikati have NOS 6 volt resistors on the shelf so I am getting one of those just to try and see how this affects things.

Cheers

Darryl

[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