1986 2.3 Electrical Problems & Cooling Fan

[KCNY]

I have a few strange things going on with my electrical system and hope someone here can help.

I've noticed 3 of my gauges fluctuating at the same time : The Oil Pressure, Gas Gauge & Temperature gauge will on move up or down, all 3 gauges at the same time as if there is an electrical spike or drop in electrical current. The needles will move about 3/8's of an inch.

The other electrical problem I notice is when the headlights are turned on, the brightness of the clock on the console will drop sharply.

In regard to my cooling fan, it won't come on when the car reaches operating temperature. The fan will come on when the AC is running but outside of that, the cooling fan does not work.

I've replaced the temperature sending unit on the engine - twice, still cannot get the fan to run during normal operation when not running AC - any solutions??

Many thanks!

 

[ethangsmith]

I can actually answer all 3 of your questions.

The gauges moving would be a failing instrument cluster voltage regulator. It is mounted to the back of the instrument cluster and is plugged into it with what looks like a 9V battery type connector. I think NAPA and Advance Auto/Auto Zone still have them. Be sure to not get the voltage regulator for the alternator. When you remove the instrument cluster, you will see the little silver box on it.

The interior lighting is supposed to dim with the headlights on. There is a resistor harness that is used when the light switch is pulled. Completely normal.

The engine fan is controlled not by the sender on the engine block, but a switch threaded into the heater core pipe. Follow the small heater core pipe that comes off the thermostat housing back towards your heater core and you should find the switch there. Quick way to check if it is the switch versus the wiring: Turn your ignition on (key in run position) and disconnect the wire from the coolant fan switch in the heater core pipe. Touch the disconnected wire to a good ground. The cooling fan should instantly turn on. If it does, the switch or the ground for the switch (the pipe that the switch is threaded in to should have a ground wire coming off of it) is bad. If the fan does not turn on, follow as much of the wiring as you can and check for any bad connections or freyed wires. Also, under your dash, close to where your steering column comes through the firewall is the fan controller. That could also be bad, but I would suspect your switch in your coolant pipe is to blame. Basically, the way the electric fan system works in that car is that if any of the switches (A/C or coolant pipe) ground, it completes a circuit, which activates the relay under the dash to turn your fan on. I was having issues with my car running a little hot at times and the coolant switch not tripping, so I spliced a switch to ground in under my dash so I can turn the fan on or off when ever it is needed. Works great.