Cluster F*** Electrical

[JD1964]

Subject vehicle: 93 convertible 5.0.

Previous owners messed up alot of stuff including a hack job harness tuck into the fender wells.

We are chasing multiple electrical issues including but not necessarily limited to;

1) Brake light circuit blows fuse the moment you step on the brake.

2) Wiper motor moves really slow.

3) Windshield washer pump runs when dash light dimmer is rotated from side to side.

4) Turn signal indicators in dash glow at random times.

5) Fuel pump cycles when headlight switch is turned on (key off)

I'm sure there's more that we haven't recognized yet. We've been tracing the harness to look for damaged wired and looking for corroded connectors etc.... Any tips in helping us track this down are greatly appreciated. Any specific areas we should be looking?

 

[jrichker]

The wiper motor does not have a resistor pack inside it. It does have one armature brush offset from the other two and a cylindrical permanent magnet instead of a set of field coils. The two brushes directly opposite each other are the low speed brushes. The low speed brush works in conjunction with one of the high speed brushes to provide a second speed.

Self Parking mechanism:
The self parking mechanism is copper circle glued or stuck on the wiper gear. The circle always has 12 volts on it until the wiper comes to the park position. There are two copper spring switch contacts, one provides power to the copper circle, while the other provides a path to the low speed winding. The power contact always provides power to the copper circle except when in the park position. The low speed contact is always in contact with the copper circle. When power is turned off at the wiper control, the 12 volts continues to flow to the low speed motor brush until the wiper blade returns to the park position.

Interval Governor:
The interval governor is a fancy electronic switch that sends the motor a pulse of electricity that varies in duration time. It always runs on the slow speed motor brushes. Turn the wipers on and quickly turn them off. The self parking mechanism inside the motor makes sure that the wiper blades come back to the park position and stop there. The interval governor does the same thing: it sends power to the wiper motor and then turns it off. The duration of the pulse sent to the motor determines how many strokes it makes before stopping at the park position. If you watch carefully, you will notice the wiper blade speed is constant and never changes when you are using the interval wiper function.

Troubleshooting:
All tests done with the ignition switch in Run or Accessory position and wipers on.
1.) Look for constant 12 volts on the red wire on the wiper motor. No 12 volts, the fuse is blown, bad wiring or bad connection. This will cause park problems or no wiper operation
2.) Check the ground. No ground and nothing works, bad ground and you get intermittent operation.
3.) No high speed operation, low speed OK. Look for 12 volts on the Dark Brown/orange wire. No 12 volts, bad wiper switch, bad connections or bad wiring.
4.) No low speed operation, high speed OK. Look for 12 volts on the white wire. No 12 volts, interval governor faulty or missing, or bad wiring. Since this is a pulse and not a steady voltage, a test light used in parallel with the voltmeter may be a better indication of operation
5.) Motor low speed test: Jumper the brown/white wire on the interval governor to the white wire. The motor should run in low speed mode. I haven’t tested this yet, so use caution. If the motor does not run, the low speed brush may be bad.

Do all this and by that time, maybe I’ll have figured out some simple tests for the interval governor…

See How to Wind Up Your Windshield Wiper Motors – Windhshield Wiper Motor Fix for more help.

 

[mikestang63]

John, Mustangs with hacked up wiring are cars I will not consider buying. You can spend months and tons of money chasing down the gremlins. Often I fee the best bet is to start with a completely new ( junkyard or replacement) set of haneses rather than trying to patch together a hack job. Now Ford has multiple different engine harnesses depending on the year, engine and transmission,

TIme to break out the DVM, test light, and patience and start at it.

 

[JD1964]

My son bought this particular car on his own and didn't ask me to help him look at it. By the time I knew about it, the deal was already made. Live and learn for him I guess. I'm just trying to help him fix stuff. We're making progress but have a ways to go yet.

 

[mikestang63]

My son bought this particular car on his own and didn't ask me to help him look at it. By the time I knew about it, the deal was already made. Live and learn for him I guess. I'm just trying to help him fix stuff. We're making progress but have a ways to go yet.

Well it will be a good learning experience for sure. Definitely has shorts/grounding issues but you know that. Problem with electrical hack jobs is they can easily llead to fires and burn down the car.

 

[JD1964]

Well it will be a good learning experience for sure. Definitely has shorts/grounding issues but you know that. Problem with electrical hack jobs is they can easily llead to fires and burn down the car.

Yep. The first thing I showed him is loosen the battery post clamps. That way if something starts smoking while we're poking around, just run up front and pull a terminal off the battery.

 

[FoxMustangLvr]

Yep. The first thing I showed him is loosen the battery post clamps. That way if something starts smoking while we're poking around, just run up front and pull a terminal off the battery.

For that exact reason I'm really happy I have a battery cut-off switch. It gives me peace of mind when working on my car.

 

[JD1964]

We figured out why the brake light fuse was blowing. The harness through the trunk area was chafing on the top of the shock which was loose and bouncing up and down. Next is to figure out why the fuel pump cycles on when the running lights are turned on.

 

[JD1964]

Forgot to mention. They also had un-insulated spade connectors for power to the aftermarket gauge lights. The connector was grounding out and blowing inst panel and radio circuit.

 

[JD1964]

Man! I was just about to push this thing off a cliff. But I finally found the problem. A bad ground wire above the fender well. All part of the jack legged wire tuck done by a previous hack owner. Fixed that and the remainder of elec issues are corrected.

If my son brings home another car like this, I'm gonna kick his ass!

 

[FoxMustangLvr]

If my son brings home another car like this, I'm gonna kick his ass!

You just wouldn't be a good Father if you didn't. Congrats on solving the P.O. hack problem.