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

[Big D]

Gidday all,

Thanks for the replies. Yes, I reckon you are spot on with the resistor being the wrong type. I did some more measurements tonight with the voltmeter. With just the ignition switch on, the voltage is 6.1 volts on one side of the resistor and 1.63 volts on the coil side of the resistor.

When the inspection lamp switch is turned on (without the inspection light plugged in) the voltage on either side of the resistor is 5.87 volts and 5.45volts.

Somehow it still seems to drop down to 4.2 volts at the coil but I am unsure how.

As you all say I need to get the correct resistor and remove the little hotwire from the inspection lamp switch and that should do it.

I'll try Ajays Rob.

Thanks all for the help.

[Lynn Eades]

Heres some pics. The resistor is thewhite ceramic on the left side (close up)

[Big D]

Hi Lynn

Thanks for that. It is quite different from the one on my panel. I'll do some hunting and see what I can find.

Cheers

Darryl

[Lynn Eades]

They come in various forms. You will see its on a board with the cutout.
these were fitted to all ford v8s with the football distributor.
I have seen them with a fuse only(and resistor of course)
The other thing you can do, is buy an adaptor, that allows you to fit a standard coil (6volt), that does away with the resistor.

[charlie fitton]

...were also used on the ford tractors and such, they're pennies a pound through an after-market parts supplier.

[Mike K]

With those 6 Volt systems, running a 4.5 Volt coil, make sure your regulator voltage setting is not set too high.. it's best set at around 7.3 Volts or so... Higher voltage = more current = more heat in that resistor.

My 1941 11d truck had one of the original Ford ceramic resistors and it got very hot , causing loss of voltage at the coil.. I reduced the regulator setting to about 7.3V ( it was up at about 8V ) and the problem was not as bad, although it did continue playing up to a degree and I never really solved it - despite trying a NOS coil and various resistors.

As Lynn said, some people use an adapter, do away with the 4.5 coil system and mount a 6v coil away from the distributor/motor altogether ....

[Big D]

Gidday all,

Thanks for the replies. I actually acquired an ‘official’ 6 volt resistor today and fitted it into the system.

Interestingly this time, the voltage at the coil side of the resistor was 2.6 volts – up from the 1.9 volts with the previous resistor. The voltage on the other side of the resistor is 6.4 volts.

It also measures 2.6 volts at the coil with this resistor in place.

Not the 4.2 volts I would have expected though with the change in resistor.

Adding in the ‘hotwire’ back in from the inspection lamp switch brings the voltage back up to 4.2 volts at the coil. Strange!

I guess it is possible this resistor that I put in is faulty and it has stepped the voltage down too far.

I should have another resistor to try by the weekend, to confirm one way or the other.

Mike – I’m interested in the voltage regulator setting you mentioned. If that was wrong, would that not affect the voltage going into the resistor?

Like you say, fitting the 6 volt coil might save me time in the end but I’m at the point now where I’d like to find out the cause of this.

Cheers
Darryl

[Big D]

Gidday,

Just out of interest I left the new resistor in place, removed the 'hotwire' and fitted the instrument panel back into place. I flicked the ignition switch on, applied full choke and turned the key and within a split second the engine fired into life. That would be the quickest it has ever started for me.

Voltage at the coil was 2.65volts on start up and then lowered to about 1.5 volts as the engine warmed up. I would have thought this would need to be higher for a 4.2 volt coil, but maybe not.

I'll try another resistor and keep monitoring things and see how that goes. I'll also try another voltmeter to make sure I am not getting false readings.


Cheers

Darryl

[Mike K]

Originally Posted by Big D

Gidday,

Voltage at the coil was 2.65volts on start up and then lowered to about 1.5 volts as the engine warmed up.



Darryl

Hi Darryl,

The volts at the resistor (and everywhere else!) should go up after the engine starts , not go down .. the gene should kick in and charge the battery at a nominal 7.4 volts or similar, depending on the regulator setting. Your volt readings make no sense ! Does the ammeter on the panel show a charge ?

Yes, a good idea to get another voltmeter and check it.

I know those 4.5 volt coils do behave strange.. I often had a almost dead flat battery and the motor would barely turn over... it would growl and just manage to get over a compression point... despite all of that, the motor would fire and start

Mike

[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

[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