Changing Wiring Harness

sam-tip · #1 (**permalink**) 05-20-2007, 08:24 AM

I was wondering how much of a pain it would be to change my wiring harness.
It is a 1990 classic roadster. Old harness with Chevy LT1 computer controlled motor.

Will this be a cut and paste or a swap?

Each year my problems get a little worse. I am getting low voltages every time I turn something one. So low of a voltage my electronic speedometer will not work when I turn the lights on.

Is this something that would require me to pull the body off of the car. I don’t want to pull the body. Then what about matching up the wires with the wiper motor. I also have the DV stirring column with remote key.

I am planning on changing my fan wiring to a Spal PWM control. So that should help with some current and voltage issues.

onefastmustang · #2 (**permalink**) 05-20-2007, 08:47 AM

Have you checked all of your ground connections?? That sounds to me like what may be your problem. And of course make sure you have a ground strap from motor to frame and check those connections as well. They be getting corroded. I had this happen to me once on an old mustang I had. I took all of the connections apart, cleaned them and voila.. No more electrical issues.

tcrist · #3 (**permalink**) 05-20-2007, 09:59 AM

Onefastmustang is correct. You should check all of the grounds. Question, Is this a recently completed kit? If so then maybe you need to add more grounds. Did you make sure that you removed the paint in the area that the ground wires attach? This would insure a better connection. If this kit has been on the road for a while (and working correctly) especially in a moist climate there more than likly is a corrosion issue. Remove all grounds and clean the areas of all corrosion. If all of this doesn't work CRII sells a new wiring kit that is designed for Chevy application. The manufacture of the kit is easy to work with and if you have a special wiring setup that the kit doesn't cover all you have to do is call them and they will walk you thru what wires to hook up where you need them. But first check all of the grounds for corrosion and/or paint.

Terry

sam-tip · #4 (**permalink**) 05-20-2007, 12:48 PM

Its been on the road now for three years. Yes I have a ground strap. Its been an issue since I put it together. But now it is worse.

onefastmustang · #5 (**permalink**) 05-20-2007, 02:11 PM

Hmmm.. it still sounds like a ground issue to me.. I would try cleaning them and/or adding more of them before I would rip out the entire wiring system. Are you grounding to the frame or did you run all your grounds back to the engine compartment.

sam-tip · #6 (**permalink**) 05-20-2007, 03:07 PM

Everything is grounded to frame. I am planning on changing the dash so I was thinking of improving the wiring at the same time. I think most of my problems is in the dash wiring. I even put relays on head lights so they did not draw power from the dash. Now I think it is all the instrument dash lights that are pulling the power down. I think if I unhook some of the instrument night lights the speedometer might work at night.

I do have a voltage gauge in the dash. It is all over the place. From 9 to 18 volts depending on what I have running. Some of that is the alternator voltage regulator.

I think if a replace the wiring harness with a better harness it will help me with my alternator problems.

tcrist · #7 (**permalink**) 05-20-2007, 03:16 PM

I agree that it is probably a grounding issue. Fiberglass cars need a lot of grounding. I would go that route first as it has been an issue since new. Its probably getting worse with time because of some corrosion. You might also take it to a shop that specializes in auto electrical. Have them check it out and see what they say.

Terry

onefastmustang · #8 (**permalink**) 05-20-2007, 05:25 PM

Hmmm. have you checked the output on your alternator??

sam-tip · #9 (**permalink**) 05-21-2007, 08:14 AM

Yep. Works fine for first ten minutes then when it gets hot voltage will varry. I took it in to get regulator replace today. Still want to upgrade harness to something better if possible.

I wonder if the blue wire that activates the alternator is getting bad voltage and then causing problems with the alternator.

priobe · #10 (**permalink**) 05-21-2007, 09:48 AM

My suggestion,

Start from scratch! I have built electrical harnesses for a Toyota Supra Turbo running a Haltech engine management and for my Cobra.

I would approach this in a manner in such a way, that you make a harness on a bench with exactly what you need ( as far a circuits). Then with a few future options such as radio etc.

By using a prexisting harness you will never be sure if the problem is still there and with a new harness you will have less down time.

Also, use relays for ignition, starter, fuel pump, headlight, high beam etc.

Just my .02