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Discussion Starter #1
When I turn my key on, the turn signal lights come on (on the cluster). Both of them. When I turn on a turn signal, they both blink. Emergency flasher do nothing. I installed a new flasher relay, but have the same results. (1) what could this be???
Also my high beam indicator light comes on when parking lights are on, off when they are off and off when headlights are on, unless i kick in the high beams, then it comes on like its supposed to. This is a wiring nightmare....(2) What is the best way to begin diagnosis? This is just the beginning of my electrical problems. Also my heater motor fan only comes on in the medium position. Just installed a new heater Rheostat, and it smokes when i turn the heater on, but has same result.(3) Possible bad heater switch?
(4) I have no power going to the washer pump. Don't know if it is the wiper switch or some other demon. I am trying to correct these issues while i still have the instrument cluster detached...
 

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sounds like it could be a number of things,,,I would start by tracing all the wires looking for chaffing spots and kinks where you may have bare or broken wires , pay attention to the wires in the steering column and where the wires go through the fire wall,,,I don't know what car your talking about,,but some of those symptom's sound like it could be a cracked/broken in dash circuit board ,,,with any luck you will find the problem tracing the wires,,good luck,,,
 

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What car, and have you downloaded and copied the schematics?
 

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I'm a little confused, on the turn signal problem, do the turn signal lamps on the corners of the vehicle work normal or do they follow the indicator lamps in the instrument cluster? It almost sounds like the ground is not good on the instrument cluster, if you have it loose to service it, it has to have a temporary extra ground as some of the screws ground it when installed. And a good service practice is to remove the battery ground cable when installing or removing the instrument panel for servicing. If the external lamps are functioning normally and the instrument cluster is at fault then I would start by using a voltmeter on the lamps in the cluster with power on for the ones you are checking and see if they have 6-7 volts across a lamp or 11-13 volts, if you have 6-7 or close there is a ground missing, if you have 11-13 or close and more than one lamp is on (exception is the dash lights) there is a short either in a switch or the wiring harness ( it could be pinched under a screw or bolts). Work one set of problems at a time, it sounds like you have several. As far as the heater blower I didn't think it has a Rheostat it should have a 3 position switch and a pair of resistors in the heater plenum box for the different speeds, a schematic would be helpful on this, I would look for pinched wires or melted insulation shorting a couple of wires together. Post your results. Good Luck.
 

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Sounds like your wiring is really messed up! I don't have a simple fix for you; you'll need to trace all your wiring and figure out what has been done to your car. It's something we all have to go through with these cars. I eventually got tired of trying to trace 47 years of wiring splices and put in a new wiring harness. Best $500 I've spent on the car. There are some good wiring diagrams on this site, as well the 1966 Ford Mustang shop manual and Mustang electrical manual are invaluable.
 

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Lets assume you are talking about the '66 mustang since you are on this site.

First, they do not have a printed circuit and main connectors, it is one on one for each gauge and light.

A little background would help. Is this how you got the car? Did anything work before? What have you done in these areas since you have had the car?

Even though it is an old car, all the wiring should not have just crapped out all at once individually. Are there a large number of splices? Are the wires the same color on both sides? As said above, look for some common item which is usually a ground or short.

One really bad thing about a '66 is the location of the fuse box which is high above the left kick panel.
 

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The heater motor issue sounds like a bad or corroded switch...you can pull it from the dash and take a look at the contacts there and see whats going on.

I'd also use a voltmeter to see if there is power at the plug towards the heater motor in each position...if not then trace backwards.

Your light issue could also be related to the light switch itself, as the power for all the lamps goes through the switch.

Has the harness at the light switch connector been spliced or damaged at all??

As far as i recall also the park/low and high beam do not run through any fuse in the fuse box at the kick panel, the switch itself acts as the fuse with its internal bimetallic strip that opens the circuit.

The switches can go bad and cause all sorts of problems, so pull it and work from there.

I'd suggest you also get the wiring diagrams and work from there, they are available on the internet for a '66.
 

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Discussion Starter #8
The turn signals on the outside of the car work fine. Just problems in the instrument cluster as far as that goes. The wiring actually is original and doesn't look to bad. I replaced all the wires in the engine compartment because that is where everything was hacked and spliced. They had the fog lights connected to the headlights so they were on all the time. I bought the foglight harness and new switch and that is about the only thing that works like its supposed to. Behind the instrument cluster there were some burned up wires that ran to the amp meter. I spliced in replacement wires there as the other ones were bare and just taped up. Everything else looks ok except for some mystery wires that are not connected and I can't really tell what color they are because they are so old. I do have all the schematics and they have helped a lot, but it doesn't help that some of these wires are not plugged into anything, and that is how it is supposed to be (Accessories and such). And then there are some that I don't know what they are so I don't know if they should be hooked up or not, I have no idea what color they used to be. I guess I will start removing switches and testing them the best that I can. Thanks for all the advice, it really helps.
 

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Discussion Starter #9
oh, and yeah, its a 66 GT coupe. with deluxe interior.
 

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Discussion Starter #10
Is the constant voltage regulator that is mounted to the instrument cluster have to also have a ground wire running to the dash? In the schematics it shows that it does, but I'm not sure if it really is supposed to, as far as a separate wire grounding to to the dash.
 

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Discussion Starter #11
Another question I have is on the cigar lighter, there is a wire coming of that looks like it might be light blue or similar, then it has a male plug on it and joins with a big orange wire. I can not figure out where that is supposed to plug into. And is it hot? Because it is just sitting there with the bare male plug. I couldn't find a schematic that shows the cigar lighter and the site that is referenced on our message board has been down for over a week.(mustang vacuum and wiring)
 

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I am going to replace the underdash main harness in my '66 because in the past it has spliced to install power windows/door locks and an aftermarket custom mustang radio (the dash metal was not cut thank heavens!)

My cigar lighter at the moment does not work and i have a few headlight issues. I have not even attempted to try and trace these issues with the existing harness, i feel the time spent trying to fix these problems can be used to install the new harness.

BTW how is your main fuse box...is it corroded up?

I feel for good insurance, 47 year old wiring should be replaced, otherwise you will spend forever chasing these electrical gremlins.
 

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Discussion Starter #13
My underdash wiring isn't really that bad. It has not been spliced into at all. My fuse box is in decent shape, just cleaned it up and installed new fuses, but as soon as I fix all these electrical gremlins I am going to update it to modern day fuses and add more fuse connections to it. I already have the parts to do it but don't want to do it until I have everything working, then if something doesn't work, I will know i broke it.
Good luck with your harness install.
 

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Is the constant voltage regulator that is mounted to the instrument cluster have to also have a ground wire running to the dash? In the schematics it shows that it does, but I'm not sure if it really is supposed to, as far as a separate wire grounding to to the dash.
The metal bezel needs to be grounded, this will provide a ground to the cvr. While troubleshooting with the cluster pulled out make sure the bezel is grounded or this will play havoc with all indicator lights on the cluster.
 

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The wire from the cigar lighter is shown as wire #40, blue/white. It should have a bullet connector to the lighter. It goes to a bullet connector which spits it off to wire #8, orange/yellow, that goes to the emergency flasher. The other side of the bullet connector goes to the fuse block. So both the lighter and flashers are always hot.
 

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Another question I have is on the cigar lighter, there is a wire coming of that looks like it might be light blue or similar, then it has a male plug on it and joins with a big orange wire. I can not figure out where that is supposed to plug into. And is it hot? Because it is just sitting there with the bare male plug. I couldn't find a schematic that shows the cigar lighter and the site that is referenced on our message board has been down for over a week.(mustang vacuum and wiring)
Here's a schematic. The bullet connector should plug into a female connector that is blue-white.

http://www.midlife66.com/wiring/66acces1.jpg
 

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Discussion Starter #17
Thanks Ranger, that is the schematic that I used to have but couldn't find it. It looks like The cigar lighter is not plugged into the fuse box, and this might explain one of the mystery wires that are just hanging around, i will go check it out. While digging further into my mess of wires, it appears that someone did some major repairs because there is a big tape ball with about 12 white wires coming out and going into another big tape ball, then original colored wires coming out if that. Looks like a major hack job and if I can't get a lot of this stuff straightened out, its time to buy a new harness. :( Anyone try the series 6 of 6 harness from NPD?
 

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I've been lucky enough that I haven't had to replace harnesses, so no I don't have any experience with the NPD harness.

I would untape that rats nest and see what you've got. It could be a simple fix that someone with poor skills really screwed up. That is probably the root of your whole problem.

If you write down the connections as they are now, then compare them to the schematic you could probably spot and correct your problems and it may not be as terminal as you think as of now.
 

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Discussion Starter #19
yeah i will do that. i might as well implement my new fuse box at the same time. there is no power going to my cig lighter or my emergency flasher. and there is no wire there to connect it to. the blue/white wire just dissapears somewhere inside a harness.
thanks again
 

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It looks like the harness was damaged or possibly even "cut through" during a repair of some stage...and has been joined together.

When you untape it...take a look and see if the spliced wires are either soldered (good) or crimped (bad) in place.

I have not used the NPD harness either, but i am going to use this one:

66 Mustang Main Underdash Wiring Harness (Alloy Metal's Brand, Concours Version) 66 Mustang Main Underdash Wiring Harness [66-UD] - $469.99 : Champion Mustang, Online shopping for Exterior & Interior Parts, Accessories, Air Conditioning, Resto-Mod &

I have heard good reports of the Alloy metal ones, which are concourse grade. I take it if its good enough for them, then good enough for me!
 
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