I've acquired a classic 1977 124 Spider that hasn't seen much action in ~1 decade. I've had it ~1 week & the most important stuff works. I've done a number of small trips around town. Yesterday in the garage I wanted to catalog everything that needs repair by flipping all knobs/switches and marking what's not working. I found that the wipers don't work (but the wiper fluid pump does) and the cabin air/defrost fan doesn't come on, and one of the air levers is locked/frozen. I left the car for a couple of hours and when I returned I thought I could smell plastic burning. I hunted for the smell & found a small electronic component under the hood that seemed like it might be hot, but I wasn't sure. I left the car overnight with the hood up and when I returned I the smell was gone but the battery was dead!
I figured I must have left something on by mistake so I went through all knobs/controls using the owner's manual to make certain that everything off (it was). Then I jumped the car & drove it around for ~20 minutes. Left it in the garage ~1 hour being very careful that the doors were closed, no lights were on, etc. & checked on it to see if the burning smell returned (it hadn't). Left it overnight & in the morning it was dead again!
I don't think that there's anything wrong with the battery or alternator because it had run fine all week with multiple short trips around town. I think it's more likely that an electrical component is shorting somewhere & draining the battery. Perhaps turning knobs & flipping switches pushed an old brittle electrical part over the edge?
My question is: what is the best way to find the malfunctioning electrical component? I was thinking of the following:
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Jump the car & recharge battery by driving around town
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Park in the garage and disconnect all fuses
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Return every ~8 hours and check the battery, if it looks OK then replace a fuse
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Repeat the above step until the battery dies
Using that approach I can isolate the bad component to the circuit running through that fuse. It's a slow process though, is there a faster or more efficient way to do this? Any other ideas as to root cause? Any thoughts appreciated, thanks!