Resistor Question

[Kevin Shelly]

Hello All

This isn't very important and only for my knowledge but I see on a lot of cars have a small resistor bolted to the firewall just under where the ignition wires come through. Looking at the wire diagram, it shows a Tan wire attaching to the top screw and a Dark Green wire going to the starter solenoid. My 58 Impala doesn't have one of these and the wire harness looks complete and not altered. What was this for and any idea why my car wouldn't have one of these? There is a location stamped on the firewall and the guy before me put this wire hold down on it, which I removed. Thanks for your help.

 

[Jim Sullivan]

Kevin, low performance engine equipped Chevys usually used a resistor wire running from the bulk head connector or ignition switch to the coil to supply power for the ignition. High performance engine equipped Chevys usually used the ballast resistor that you are inquiring about. I'm not sure on your '58 which would be correct, but I'm sure someone here will be able to provide you with the correct information for your '58.

 

[Kevin Shelly]

Hi Jim

Thanks for the info. Mine a standard 250 HP unit so I think that explains things. Most of the resistors I see are on 3x2 engines. Thank you very much again. There's so many configurations and it's taking some time to learn about them.

Kevin

 

[ragtp66]

They all used a ballast resistor in 58 it is there to drop the voltage to the coil after the car starts from 12v to about 9v to keep from burning up the coil.

 

[Kevin Shelly]

So if my car doesn't have one of these, could that be because the starter and solenoid were changed at some point to a unit that wouldn't require one or should one still be installed? I would need to change the wire harness so the wires needed could be installed correct?

 

[Don Jacks]

Kevin,your car should have resistor wire already in the harness.Start the engine and measure the voltage at the plus side of the coil.If the resistor wire is in place,the voltage should be in th 8-9v range.If not,you'll read battery voltage[12.5-13.5v.].

 

[Kevin Shelly]

Thanks Don. I'll check that out the next time I'm working on the car. Are these resistors still available for purchase?? Not sure why someone would have removed it from the system??

 

[Don Jacks]

Kevin,Most likely yes they are availeable somewhere as they were used ,either the wire,or a "block" resistor from 55-74 in GM cars.The only need to remove or by pass it would be if one went to an electronic ignition conversion.

 

[Kevin Shelly]

The folks before me removed the points and installed an electronic component in the distributor. Maybe they removed the resistor when they installed this module? Sorry I don't know much about these electrical systems.

 

[Don Jacks]

This is where the voltage test will come in handy.I have simply removed the points and replaced them with the "module" and the vehicle suffered no ill effects,while others had to receive battery voltage to work properly.I quess it would depend upon the coil to the module interface .If the car is running properly,one could leave it alone.For your own information,or piece of mind,do the test as described.If while running,the voltage is 12 plus volts,then the resistor has been by passed.This would be needed information if you wanted to convert it back to points and condenser ign.

 

[Kevin Shelly]

Sounds good. I'll get to this next week and check it out. The car seems to run OK now but I don't know if I'd know a difference because it was this way when I bought it and don't know how it ran with the points installed.

 

[ragtp66]

Kevin,your car should have resistor wire already in the harness.Start the engine and measure the voltage at the plus side of the coil.If the resistor wire is in place,the voltage should be in th 8-9v range.If not,you'll read battery voltage[12.5-13.5v.].

This is not correct on a 58 the wire going To the ballast should have 12 volts AFTER it goes from the resistor it would have the lower voltage to the coil. I am not sure what year that GM eliminated the ballast resistor and changed to a resistor WIRE my guess is 64 or 65 someone else will probably know for sure probably the same time alternators replaced generators. When they changed to the electronic ignition they most likely removed it because the new ignition requires 12v constant. If you look at the other post I put up with the 348 starter harness you will see the ballast mounted on the firewall.

 

[Jim Sullivan]

'62 and newer had the resistor wire or ballast resistor depending on application. I don't know about anything earlier.

 

[Red 409 63 impala]

I have a 63 Impala I am putting a 409 in. The only engine using a ballast resistor is a 409. The six and the 283 and 327 use a resistance wire in the harness. Some GM vehicles used different value ballast resistors depending and the engine. THe high performance used a lower value resistance and the lower performance used a higher value. This way the coil received higher voltage for the higher hp engines. The 63 assembly manual only shows the ballast resistor under the 409 option. When I purchased the under hood replacement wiring harness the 409 is a special harness to allow the ballast resistor to be used.

 

[oldskydog]

59 was the first year for the resistor wire in the harness on all but the special/high performance engines.

 

[DonSSDD]

59 was the first year for the resistor wire in the harness on all but the special/high performance engines.

So all 58's and earlier had the external ballast resister?

My 59 283 had the resister wire.

 

[oldskydog]

Yes

 

[models916]

With the HEI conversion, match the coil to the voltage at the coil. Lowered voltage was used to save the points from arcing.

 

[63impalass409]

I don't mean to high jack here but I got another question, on one of my 63's before I sold it it had a 409 in it so it had the firewall mounted balist resistor but for now while I build another 409 I am putting a 283 in it but the distributor is a hei so can I just hook it up like normal or should I switch back to the stock distributor which I don't have?

 

[Don Jacks]

The HEI MUST have full battery voltage in order to work.This can be done by either by passing the resistor/or resistor wire,or running a wire from the HEI to a switch on connection in the fuse panel.The 64 Impala that I had had the HEI hooked up to the fuse panel,as the 327 had an HEI unit on it,and it worked fine.