Chevelles.com banner

1 - 14 of 14 Posts

·
Registered
Joined
·
584 Posts
Discussion Starter #1
I have finished rewiring my '70 Chevelle all with M&H stuff. I started up the car today and my dad noticed one of my wires smoking. It was the orange/white wire that comes off of the + coil side. It actually started heating up in the harness where that wire makes a u-turn--up near the gutter area (if that makes sense). My dad burned himself on the wire. It melted through the harness tape. I suppose there is too much current running through it? Anyway, I was wondering if you folks had any ideas of what I have wrong. I plan on calling M&H on Monday, but in the meantime I though I'd try here.
Thanks.

;)
 

·
Premium Member
Joined
·
2,223 Posts
makes a u-turn--up near the gutter area (if that makes sense).

The wire is a resistor wire so the length is dictated by the resistance, the extra length is looped in the harness. It will also heat up some, for that reason it has a woven fiberglass insulation rather than plastic like all other wires. however what you're experiencing is too hot.

The only thing I can think of is that there is a second, yellow, wire on the coil + post. It connects to the R terminal on the start solenoid. If that wire is making contact with ground, either pinched somehow or burned on the exhaust/headers, it could cause the hot resister wire you're experiencing. I guess a faulty coil could cause high current in that wire also. However, in either case, you would think the engine wouldn't continue to run. :confused:

Did you notice this immediately after starting or did it run for a while? Did you need to crank it unusually long before starting?
 

·
Registered
Joined
·
584 Posts
Discussion Starter #3
Originally posted by Elree Colby:


Did you notice this immediately after starting or did it run for a while? Did you need to crank it unusually long before starting?
I have had a hard time getting the car to start. And when I could finally get it to run it would run really rough and die. It took a little while for the wire to heat up.

Thanks.
 

·
Registered
Joined
·
1,555 Posts
I assume that you're running a "points style" distributor, correct? If so, check your dwell angle. If you don't have a dwell meter, set your points for .019 and try it again. IF the points/condenser set haven't been changed recently, change them. The only time I have EVER seen the resistor wire heat up THAT much was when the points stuck closed on my wife's Chevelle a gazillion years ago! Of course, the engine wouldn't run either. The fact that your engine is running rough leads me to believe that the gap isn't wide enough on your points, so the current flowing through the coil is greater than normal. Keep us posted.
 

·
Registered
Joined
·
584 Posts
Discussion Starter #5
Originally posted by MalibuJerry350:
I assume that you're running a "points style" distributor, correct? If so, check your dwell angle. If you don't have a dwell meter, set your points for .019 and try it again. IF the points/condenser set haven't been changed recently, change them. The only time I have EVER seen the resistor wire heat up THAT much was when the points stuck closed on my wife's Chevelle a gazillion years ago! Of course, the engine wouldn't run either. The fact that your engine is running rough leads me to believe that the gap isn't wide enough on your points, so the current flowing through the coil is greater than normal. Keep us posted.
Sounds like a good idea. I will take a look on Monday. THANKS.
 

·
Premium Member
Joined
·
340 Posts
I have the exact same symptoms that Ben mentions above. This all happened after changing the wire harness on my 70 Chevelle with a new one. Same thing, the white/orange fiberglass insulated resistance wire that started to smoke and get hot after having the ignition turned to "ON" (not start). I did this to to check voltages and operation of accesories. I'm not so sure until I go to the car today (25 miles away at Mom's garage) but I think I remember my old harness resistance wire being cut short, this one is quite long. Also, I measured about 1.8 volts at the coil, is this to low? I'm thinking the excessive length of the wire is creating to much resistance increasing the current and causing the heat to dissipate in the wire resulting in smoke. I'm real close to cutting this wire down in length but don't know what is typical for a voltage at the coil terminal where this wire attaches. This is NOT a points type distributor, personally I don't think that has anything to do with the problem. I ran a search for threads on this topic and this was the most related topic. Any ideas....should I cut the resistance wire down? If so what resistance am I looking for? I am using an MSD Blaster 2 coil and a Billet MSD magnetic distributor. Oh, one other thing, the distributor was not in at the time I turned the ignition key to "ON". I will be dropping it in this afternoon.

I'm also going to e mail Ben to see what his fix was.

Thanks,
Sam
 

·
Registered
Joined
·
7,762 Posts
You could disconnect that wire, along with the yellow, from coil (+). Tape that wire connection up. Run a jumper from battery (+) to coil (+) to try and get the car started. This will prevent you from sacrificing your new harness while you fix the car.
Couple of things.
Don't leave this jumper on unless you are trying to start the car. Use something like a sleeved clip lead. The coil doesn't like to see DC voltage while the car isn't running. The coil will start to heat up because of the steady DC.
You won't be able to shut off the car without disconnecting this jumper.
If you need a dwell meter, stop on by.
 

·
Premium Member
Joined
·
340 Posts
John, Thanks...I'll give it a try. You're right there is a yellow wire and the fiberglass resistance wire together at the coil +. I'm leaving in a short while to go over to the car and get a few other things done including another look at the resistance wire. I'll check the old harness and verify the length it was. The car ran great with the wire length from the old harness so I assume I should duplicate the resistance (regardless of length). I'll keep cutting it down inch by inch until I get the right resistance to match the old harness resistance wire. In the meantime I'll run a jumper like you mentioned. I can understand what you mean by the coil not liking the DC for a length of time so I'll keep that in mind also. Thanks again.
Sam
 

·
Premium Member
Joined
·
340 Posts
Back from working on the Chevelle. I disconnected the engine wire harness from the firewall and also the resistor wire from the + coil. The resistance of the wire uncut is 2.2 ohms. Th resistance of the wire from the old harness is 1.9 ohms....not much difference. I did not get to the point where I could try to start the engine, I'll try that next weekend. Still wondering why it would heat up and smoke a little with the key in the "ON" possition. There are no shorts that I could find by eye or using the VOM. Curious about this, maybe your right John....(by the way, I'm the one from NJ, Ben is from CA) No points to adjust the dwell, so no need for a dwell meter.

I stand corrected on one detail though....I checked with the installation instructions for the MSD Blaster 2 coil and it does in fact state that you need to include a 1.8 ohm ballast resistor when using a points style distributor. The resistor would be in series with the + side of the coil. Since my distributor is pointless, I do not need this resistor. (So why the resistance wire? Maybe I should consult with MSD...

Sam
 

·
Premium Member
Joined
·
340 Posts
John,
You're right about the resistance wire. I contacted one of the Tech support people and this is the reply I got:

"Dear Sir,

You will no longer need to use the resistance wire that was on your stock ignition system. Also, you will need to bypass any ballast resistor used in the system.

Thanks,
MSD Tech"

Also right in the other regard too:
If you leave the key in the ON position it will run DC through the fiberglass resistance wire to the + coil side. (The yelloe wire receives the battery voltage during start only.) Particularly when the points are closed causing the current to flow and heat up the wire. However, once the engine is running and the points are opening and closing, the wire doesn't see current long enough at a continuous rate to heat up enough. This is true for any distributor even my magnetic. At least this is what I understand...hope the translation is accurate enough to make sense.

Sam
 

·
Registered
Joined
·
723 Posts
I had a similiar problem with a 71 camaro. Turned out I had a faulty starter solenoid. There was an intermittant short appearing on the wire coming from the solenoid to the + terminal of the coil causing the resistor wire to heat up. I actually had the coil explode on me once. Converted to Hei soon after and eliminated the resistance wire and the wire from the solenoid.

Tim
 

·
Premium Member
Joined
·
2,263 Posts
There is a dead short somewhere and that is the only way that wire will get that hot. I think Blu69 has hit it on the head or you have a wire touching at the starter. The MSD (electronic) dist needs 12V and that is why you bypass the resistor wire. The only time you need a ballast is if you use a high voltage coil with points. Be careful with what is going on because that wire will melt into the other wires and cause big problems. That is how cars burn to the ground. I know you do not want to hear this but I would open up the tape to make sure that it has not melted into the other wires and I have seen this happen. Please check them. I have wiring diagrams if you need.
Nelson
 

·
Registered
Joined
·
584 Posts
Discussion Starter #14
Yesterday I replaced the 20 gauge resistor wire in the harness with a more appropriate 12 gauge wire. I think that ought to handle the full voltage a little better. Now on to that ignition switch.
 
1 - 14 of 14 Posts
Top