1990 Dodge Caravan radiator fan

[thermaldisc]

There seems to be a lot of problems with the radiator fan circuits on Chrysler/Dodge mini vans-ALL OF THEM. We happen to be the proud recipient of a 1990 Dodge Caravan which we purchased for $1 at a car dealer who tried in vain to get us to trade for another. After repairing the head gasket and a few other ancillary items, the one remaining piece of the puzzle is this quite confusing fan circuit that someone prior to us tried to fix by installing a toggle switch inside the vehicle to manually turn on and off. This fix is fine except that my son who is 16 will be driving back and forth to Taco Bell to work and I can't get him to remember to feed the dogs or take out the trash, so I'm sure he won't remember to operate this switch correctly. Furthermore, the toggle seems to get very warm while in use indicating an excessive amount of amperage. I would like to try to "quasi-correctly" repair this last item before turning over this inexpensive set of wheels to our forgetful burrito maker. Where do I start? I'm now holding both hands over my head to indicate total confusion. Also, does the temp "dummy" light barely come on and go off in relation to this fan issue? Any help to resolve this last adventure would be great (and would get him off my back) so the floor is open folks!

[yogi_123rd]

Firstly, whether your instrumentation has a dummy light or gauge to measure the temper, it has a seperate sensor (connector has one wire) than the one to operate the cooling fans.

Your cooling fan system: Power when ignition switch is on goes to a temperature switch (connector has two wires) in the water system. The switch is either located near the thermostat housing area, water pump area, or at the base of the radiator and measures the temperature of the radiator water going into the engine. When it reaches the too hot temperature, the switch allows the voltage sent by the ignition to go to the cooling fan relay (usually found in a relay box). The relay's job is to sense any voltage from the switch and send power to the cooling fans over a seperate cooling fan circuit (there's a large fuse in that circuit).
You should be aware that most cooling fans also a hi-speed/low speed operation and the AC system is tied into them. Typically, when the AC is turned on, the cooling fans run on a low speed setting to run air thru an evaporator. Ensure the AC is off when troubleshooting.

Checks you can make:
1. Locate and check the fuse for the cooling fan motors. Whoever hot wired the toggle switch in may have bypassed this fuse which may be bad.
Sometimes the fuse is located in a seperate box under the hood where the relay is found too or it could be under the dash.
2. Locate the temperature switch. Remove the connector. One side of the temperature switch should have voltage when the ignition is on. If there's no voltage at the switch, the wiring coming from the ignition is broken.
If it has voltage, use a paper clip or jumper wire to connect both wires in the connector. Power will then go to the relay side of the circuit.

a. If the cooling fans come on, replace defective temperature switch.
b. If the cooling fans don't come on, you may have a bad relay. Try replacing it. If they still don't come on, bad wiring to/from the relay is the problem.

Most problems resolve to be a fuse, the temp. switch or bad relay.

Hope that helps

[thermaldisc]

yogi 123rd,
Thanks for the great advice. I shall post the results of your recommendations in a few days. What an incredible web site....thermaldisc