Chevrolet Repair: 87 Chev Celebrity Cooling Fan, coolant temp, repair attempts

Question
QUESTION: The lo-milage Celebrity ran fine at midnight last night but this morning the battery was almost dead and the cooling fan was running. I disconnected the connector from the coolant temp sensor - the fan stopped and did restart when I plugged it back in. I have the factory manual and know that the sensor talks to the computer and the computer talks to the fan relay when necessary.  Replaced both the sensor and the fan relay and everything is fine tonight but I'm not very confident that I've fixed anything. In my mind the computer is the next suspect but would not suspect it to be intermittent so maybe it's a intermittent in the wiring harness.  Any tips.  Regards, BC

ANSWER: Taking a guess, I'd have to say the relay was the defective part. It was stuck on. The ECM just sends a ground signal to the relay when the cooling fan is needed to come on. But the relay also needs a 12v ignition on signal to activate the contacts. I'm pretty sure you already nailed the problem with the relay. If not feel free to get back to me with more info.

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QUESTION: Thanks for your feedback Robert but as I feared, I did not fix anything yet.  I recharged the battery yesterday after my repair attempts and all was good when I went to bed. But when I got up this morning, the battery was dead again. After a big battle with vise grips, I got the damn side-teminal cables off the battery and the resistance between them was 7 ohms.  Went inside the car and found the glove compartment door wasn't completely closed.  Closed it and the resistance was in the thousands.  Was estatic to think I had found the problem that easily.  But to be sure, I opened the glove box again and the resistance stayed in the thousands of ohms.  I pulled out my deer rifle ready to put a round through that little four-cylinder but sanity prevailed.  One thing I noticed that I can't explain is that when checking the resistance between the positive and negative battery cables, it starts at at about 24K ohms and gradually drops to about 18.5K.  And it's repeatable.  Is there some big capacitor soaking up the little current from my VOM until it gets full or is this a symptom that I should worry about.  Thanks for whatever new ideas you might have. Regards, BC

Answer
I think the glove box light was most likely the cause of the recent battery drain. To be sure you can test for a parasitic drain on the system. The best way to do this is to disconnect the negative battery terminal. Install a digital ammeter to the disconnected negative battery terminal and the other lead of the ammeter to the battery negative (you'll have to put in a 3/8 bolt in the battery). Your ammeter should read less than 40 milliamperes. That would read as .040 A. If it's at 40 milliamperes or less there is no drain. Over 40ma just slightly there is a small drain. Open up the glove box and should jump up to about .500 Amps or higher. Also check your trunk light for sticking on.

Make sure you wait about 15 minutes before using that meter reading. It takes awhile for some of the modules to power down to sleep mode.