Hey guys, I have a question. Should your engine wiring harness (that comes from the firewall and runs the starter, coil, temp sensor, oil sensor, wiper motor, and heater blower motor) get warm when you turn on your ignition (without starting the car)? Here's my story: Ok, so I have a 63 Impala with the 283/Powerglide bone stock car. Yesterday, I was working on the wiper motor to see why it quit working on me. (Car was in the garage) I've had it unplugged at the dash wiper switch for a few months, so I plugged it back in last night and turned it on....NOTHING. I pushed the button for the washer and it was clicking, so I think it still works. I wanted to test the prongs on the motor to see if I was getting power, so I turned the switch on and grabbed my test light. I unplugged the plug for the motor and checked.....NO POWER. Here's where my problem began. I went to plug it back in to the motor and all of the sudden, I heard a loud thump (like a relay tripping or something), and all the power to the car died. I had the doors open with the interior lights on and the radio was playing. Now, the whole car was dead, like it didn't even have a battery hooked up. For about 5 minutes I touched my test light on terminals to see if i was getting any power anywhere, but nothing. Then all of the sudden, the lights inside the car came back on. I figured the wiper motor had a short or something, so I unplugged the 2 harnesses to the motor and to the wiper switch under the dash, so no power would be going to it. As I was looking at it I noticed the harness wires from the firewall plug over to the coil was really warm. It wasn't hot enough that it would burn you, just really warm, which is usually what happens when you have a short somewhere. At that point, it was getting late and time for dinner, so I decided to just back it out and put it back in the driveway where it usually is. I cranked her up and backed out into the driveway. It was dark so I pulled the light switch to get lights, and then the car died :/ WTF? So, I turned it back off, restarted the car, then parked it in its spot. I let it run for a minute, then pulled the light switch again, and everything came on and worked just fine. I have no idea why it did that. Again, that makes me think something is crossing somewhere or something. I researched it a little, then today I went back outside to get a good look at it in the daylight. I hooked the battery up, but the wires were fine this time. Then I turned the ignition on again and that area of the harness started getting warm again. So, my question is....Is that normal? Should that harness get warm like that, or do I need to start checking for a short somewhere?
I had a similar problem with my 64 Belair, 327. I am not an electrical troubleshooter by any means. My mechanic told me, over the phone, next time you start the car grab the engine harness at the firewall and rock it. Sure enough the car would die. I cleaned the terminals in the harness and firewall. End of problem. I should replace the harness, and will do so when I put the car back on the road. Sent from my SM-T377V using The H.A.M.B. mobile app
There is a wire in that harness, which is actually a resistance wire, that connects the ignition switch to the coil. When you leave the key on, if the points are closed, you will be sending current through the resistor wire, and it will get warm. That's what resistors do. So, yes, it is normal.
Lot's of stuff to digest in your post. Sound's like you lost primary power source. But since I do not know where Chevy provided that source from (at the started or at the battery) on your model car I can't help much. Therefore what Squirrel is saying may be only a normal thing and not a bad thing. The best thing to get yourself is a wiring diagram for your model car and go from there. Those drawing are your or anyone's best friend.
I do know the main power runs through that harness, because when I first got the car, it would randomly lose all power to the car. After jiggling around on the harness, it would come back on, so I unplugged it from the firewall (engine side) and noticed the main power wire prong was messed up, so it wasn't getting a good connection. I did some doctoring on the plug housing and it's been good ever since.
The coil type could make a difference....they have a "primary ohms" rating, if it's lower than the stock coil, it will kind of overload the resistance wire.
Don't know if the failure was from the current load or corrosion; but back in the day we used to reroute the main power lead around the plug. No more problem.
I would unplug the firewall connector and look closely at all the pins, I bet you find some green ones. Got a manual? That should show you what harness section you may need, some of those are available. By 1963 wiring had gotten a little more complex and I'd prefer to get something already made up.
That was my next plan if it kept dying on me after I fixed the existing plug. I think it might be time to just replace it anywasy. It's $75, but would give me peace of mind.
I don't have a manual yet, but I do have the engine compartment wiring diagram. The car has two harnesses under the hood. One deals with the engine, starter, coil, oil temp, water temp, heater motor, wiper motor. The other one runs all the headlights and horn. It's pretty straight forward there. I just need to research a little more from the fuse box to the dash inside the car. Maybe, there's something going on there. Everything under the dash looks practically brand new though, so from what I've inspected so far, I shouldn't have any issues there. I actually thought they rewired the car when I bought it, because it was in such good shape.
usually the wiring under the dash is in much better condition than the wiring under the hood. Something about not being exposed to the engine heat? Pictures....
I know it impossible but if he was able to show the insides of the fuse box (the wires and their terminals) it would tell us if it heat generated from resistance is present.
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