Battery wires getting HOT!! / No instrument cluster lights

[SC MM 88]

87 MM 4x4. The smaller set of wires on the pos batt side(not the large starter wire) are getting really hot along with the lil white block mounted next to the coil. I started having problems when I removed my instrument cluster. Im particular about my work and careful not to pull pinch any wires. But my green instrument cluster lights are not working but everything else (seatbelt, egr, speedometer is working and other warning lights etc.) are. So I'm left with a very hot +batt small wire leads and lil white box beside the coil and the inside instrument cluster . Not sure not sure what's going on but if anybody out there can steer me in the right direction be greatly appreciated I'm a little bit better at mechanical side butt the electrical I have a lot to learn. Thanks

[camoit]

The white coil at the coil is a dropping resistor and it will get hot. There made out of ceramic so you can break them. But the other wire might get warm with the lights on. Hot is because of resistance in the wire. You should check for corrosion in the wire. Slice open the insulation at the clamp or look for Elephantiasis. If you have ether your going to need to fix it.

[geezer101]

The ballast resistor (the ceramic block mounted to the coil) should only get mildly warm. If it is getting 'hot' there's an issue in the ignition circuit somewhere. +1 on camoit's recommendation but also go through your ground wire connections as well. They are notorious for causing the majority of electrical gremlins. Disconnect the ground leads to the engine and chassis and give the eyelets and bolts a thorough clean with degreaser, then scrub them with steel wool, wire brush etc to remove any corrosion on them.

p.s. did you lose your parking lights when the instrument back lights failed? If the parking lights are still working, check the instrument dimmer switch. They can go funky and cause the back lights to blink off. If all the parking light circuits are out, start with fuses first. :thumbup:

[camoit]

Geezer Don't take this wrong but. They get hot at idle and will cool down as the RPM increases.
The faster the RPM the less they need to do because the time to charge up the coil is reduced.
It's the hole Ohm's law thing. year built + miles divided by resistance = truck problems

[geezer101]

lol. I was referring to it being under load but it's all good. Ignition components do get tired and they will start to glitch after 10 years and normally die at 15 years.

[SC MM 88]

I changed the resistor coil last night and then cleaned all my grounds(engine block, frame) all the way to the battery. For some reason the resistor coil is still getting hot as a firecracker?????

[geezer101]

I don't know how hot the resistor is meant to get but if it isn't breaking down and is cooler to touch after it's been out on the road and done a few cycles, I'm going to say it's fine. Any luck with the back lighting yet?

[SC MM 88]

Yes geezer101. The speedo was fried. I guess the electronic board on the back had a short because I replaced the speedo with a good used one and bam I've got instrument cluster lights! I'm just still a lil weary about the ballast resistor on my 87 MM 4x4. This thing gets so hot if I touch it I literally get burnt??? But everything else to my knowledge seems to work properly on the truck

[geezer101]

Anyone know the resistance value on the ballast resistor on these? If you can get your hands on a multimeter and check it, you might get an idea of why it's in roasty toasty mode SC.

[SC MM 88]

Geezer101, everything seems to be working fine other than that resistor being hot. It just plain baffles me

[SC MM 88]

Which wire do I need to focus on camoit? I've cleaned all my ground points from the block to the neg batt post. When you say elephantiasis what do you mean by that? I appreciate any input I've went through everything I can think of

[SC MM 88]

Is it possible to do away with the resistor?

[camoit]

No. It keeps from burning up the pick up coil in the distributor.
Remove at own risk of being stranded. If you think it's getting to hot go get another one.
Elephantiasis on trucks is just like in people. The wire will get larger from corrosion inside the insulation.
So how hot is HOT? warm to the touch or 2 Mississippi HOT. That's where it's hot enough you can't touch it.
All wires will get warm. It's part of how electrons flow. It's also what makes the circuit breaker on your house trip. They have heater in them. Also the sun will heat them up and they will trip more easily if in direct sun.
So warm is fine HOT is bad. Resistance causes heat. Broken strands of wire = Resistance = heat.
Corrosion = Resistance = heat

[maxdsm]

Not to jump thread .... but I have a accel single coil pack that gets hot as well . I'm not sure if it's due to doing away with the resistor ? Some coil. Packs have built in resistors not sure if mine does or not .My question is if I add the ballest resistor to the coil will that get rid of it heating up so much? If some one on the forum has a picture of how there ballest resistor is hooked up to there aftermarket coil pack please post here .thanks.

[camoit]

Coils get hot. There just a large capacitor. They are resistance in the flow of electrons to ground. Resistance = heat. That's why many of them are oil cooled.