Back of ignition switch gets hot

[rar7775]

I've scoured the forum to find an answer or at least a similar problem to mine but to no avail. So here goes:

I have a 72 240z currently running with pertronix ignition. It runs great excecpt the back of the ignition switch gets hot.

A few years back i had the same problem but didnt catch it in time and a wire going to my ignition switch got hot and melted the plug on the back of it. The morons who replaced the plug cut the wires instead of pulling them out of the burnt plug and then replaced the plug. Long story short, i had to replace the pertronix back to points.

After the car sat for some time and when I had the money to replace the pertronix I did. Now I'm having a wire(s) and the back of the ignition switch getting hot again. I'm not really sure if the wiring of the pertronix is the culprit or just a coincidence because it sat for so long and didn't drive it enough with the points to notice burning wires and what not.

Anyway, what kind of wiring mistake could cause all the burning wires and switch? I've worked on it alot these past few weeks and have found some things but nothing that has stopped the wires from getting hot.

Any help and ideas are GREATLY appreciated!! Thanks in advance

[beermanpete]

It could be a problem in the igintion switch causing the heat. If the contacts inside the switch are loose, dirty, or worn out the resistance will rise and cause heating in the switch.

Check the voltage drop across the switch. If you measure more than a few milllivolts across the switch it is likely the problem.

[d240zx2]

Generally speaking, something getting hot like that is the result of a loose or ill-fitting electrical connection. As beermanpete said, loose dirty or worn out connections will increase resistance in the circuit and cause the problem. The problem being at the switch is, I think, co-incidental to the actual problem.

[rar7775]

Thanks alot guys! I'll be working on it tomorrow and that gives me some new things to try. I'll keep you posted.

[rar7775]

Ok. After working on it all day yesterday this is what happened:

We replaced the ignition switch and found that we were getting 17.5-23 volts to the power wires while it was running! So we instantly thought it was the voltage regulator and went to the parts store and they confirmed that. However, after replacing the voltage regulator it did the same thing! 17.5 volts at idle and about 23 volts with some throttle. What the hell?! We're totally stumped. Could the voltage regulator somehow be bypassed?

We checked the wiring at the coil and pertronix. Here's what we found:

The solid black wire seems to do nothing and the 2 BW wires when wired properly (the powered BW, when the ignition is in the on position, is placed on the same side of the ballast resistor with the red pertronix wire and the GW wire on the opposit side of the ballast resistor and the negative wire out of the pertronix is to the neg side of the coil and the other BW wire is to the pos side of coil) the car starts but won't run. If we put the powered BW wire on the same side of the pertronix as the GW wire it runs. All the while with 17.5-23 volts running on all power wires.

Again stumped. The solid B wire seems to do thing because with both wire "settings" stated above we can leave the solid B wire off the coil with the same results.

Any thoughts?? Thanks again in advance.

Richie

[Mikes Z car]

Is there a possibility if it is a digital meter that it might be reacting to the voltage pulses from the coil and an analog meter might give a different (lower) reading? If so would the digital meter give a different measurement at the battery due to the battery absorbing the pulses?

[SteveJ]

Here is what happened: you or a previous owner changed the alternator to one that is internally regulated. DO NOT RUN THE CAR until you get this fixed. How easy is this to fix? Pretty easy. Buy this plug (For those of you who do not feel like clicking the link, it is the jumper that MSA sells for the alternator upgrade.). Unplug the voltage regulator. Plug in the part you bought.

How sure am I that this will fix your problem? Pretty **** sure.

[rar7775]

Thank you everyone for your ideas! My battery is also at about 18 volts so I'm sure the volt meter is correct.

I just ordered that plug for the external VR bypass. I've had this car for years and had to replace the alternator more than once but this is an upgrade that I should do anyway and I'm sure it'll probably fix my problem. I'll keep you guys posted when I receive it and install it next weekend. Thanks again!

[rar7775]

Ok so today I had my alternator and battery tested. The alternator was a 60 amp with an external voltage regulator. The alternator passed but the battery didn't. The battery was newer than the alternator and they said it was actually undercharged. I'm so confused. The alternator was putting out a bunch of watts at the ignition key but I guess I never checked the voltage at the battery.

So I replaced the alternator with an 83 280zx turbo and plugged in the MSA adapater ug They told me its rated at 60 amps. Everywhere else I researched said they're rated at 70. Anyway I replaced it and the battery, cleaned the pos and neg connections at the starter and saw a slight improvement.

At the ignition key I got 22 volts at first but after about a minute it dropped to 18.7 and stayed consistent at idle and at about 3000 rpm. Then I checked the voltage at the battery and it stayed at about 22/23 volts at idle and 3000 rpm.

The upgradeded alt seems to make the car run a little better and it did drop the voltage at the ignition key.

I do have a fan and a water pump hooked up the ballast resistor. Is that possibly drawing too much power an making the ignition wires get hot? What else could be the problem? I'm really at a loss here...

[SteveJ]

Either your voltmeter is wrong or you still have a problem with your charging system.

By the way, what do you mean that you have a fan & a water pump hooked up at the ballast resistor? What current are they rated for? If you are drawing too much current through the ignition, you could heat up the switch. Auxiliary items such as electric fans for cooling the radiator should not be powered through existing circuits since they could potentially overload those circuits.

[Zed Head]

What kind of voltmeter are you using? Sounds like an old analog meter that hasn't been zeroed or is just no good. Or a digital meter on the wrong setting.

Measure voltage at the battery with the key off. Better yet, measure voltage at the battery on a car that is working properly.

Post a picture of your meter as you've been using it.

Edited February 19, 2012 by Zed Head

[rar7775]

Ok. Sorry I posted that last comment really late last night and I was pretty tired. I have an electric fan and an electric water pump hooked up to the side of the ballast resistor that the GW wire is on. I'm going to disconnect them and see what kind of volts I'm running then. If that is the problem, any suggestions of where I can power them so I do t have use a separate switch?

When I connect my multi purpose meter to the battery when it's off it reads about 21 or so and when I connect it to my 01 town car it reads pretty much the same.

I'm posting this from my phone so I don't know how to post picture. I'll try to figure that out so you guys can see...

Richie