'87 SR5, 4speed fan
Alright, so I finally decided to mess with my fan resistors since I lost my two low speeds a while ago. I followed this website can removed the resistor pack:
The two bad resistor coils broke close to the soldering point, so I tried resoldering them. This worked for a few days and I was able to enjoy my low and medium-low speeds, but they burned up again. The coils looked pretty bad and there was no saving them.
Then I got an idea before going out and buying a replacement
Since the 3 resistor coils sort of act like a manual potentiometer (controlled by the heater switch), why wouldn't replacing the bad resistor coils with regular, carbon film resistors of equivalent resistor values work?
I measured the resistance of the bad coils and they were really high, over 1Mohm each. The good coil which controls the high speed fan was only a couple ohms. Well, just to experiment, I installed a 40ohm resistor and 100ohm resistor in place of the bad coils. Plugged it in and couldn't get anything. I was puzzled why it wouldn't work. Even if it was a power handling issue I'd at least blow up the resistor or see some sort of response.
I verified all positions of the switch is working by short circuiting the resistor pack for each switch location. So I could go through low-med1-med2-high and they would all give me the high fan response (since there is no resistors reducing the current through the fan).
Only thing I could think of is the resistors I used were still too high...but I don't have a new resistor pack to measure the resistance. I haven't got a chance to mess with it anymore but I could go get some resistors of lower values and try them (40ohm is the lowest I have on hand). There may be a power handling issue with the resistors since they are only 1/4 watt, but still I should see something happen since I am completing the fan circuit.
Any ideas? Yes yes I know...just go buy the replacement. But, I like to tinker around and now that I have this problem its bugging me