Something blew up in the trunk area....

I am currently doing assembly work on my car after a frame off restoration. Fiberglass is back on the frame, doors and various panels are on and car is running and driving. Speedometer and DIN faceplate with radio and various controls and switches are connected. Main harness and engine harness is new, fans, all fuses and relays are new. The other day I was changing the diaphragm on the ac controls, filled the gas tank up half way to check the fuel sender, and filled up the washer fluid to check the pump. I had the ignition on, and when i turned it off I could hear a loud pop or poof if you like coming from the trunk area. This happend three times. Have not had any problems prior to this, nor after.... Any idea what it could be? Some suggested the Wire, pigtails part#: 108562 for the fans. There are only two of them though.... I pulled off the connetors for the otterstat and jumped the fans and they worked. So I guess the pigtails are okay?. Had the car running til it got past 220 degrees. I would say 228 degrees... and the fans did not start. They should have started by then? The fans did start before all this happend, but I cant remember how hot the engine was. Thermostat is new, otterstat is new and mounted upside down. Any idea folks?
After the 2nd time I heard the sound, the fuse for the high beam blew up a few seconds later while pushing the light switch. Changed the fuse, and has not happend since. (Did also change the switch after this, because it tended to stick and the button was starting to fade.

Did you smell anything or see any smoke?

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Originally Posted by Lwanmtr

Did you smell anything or see any smoke?

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No smell, no smoke!

Check the wiring and look for anything that looks burnt. Check all the connectors to make sure they're not loose or have burn marks. also look at any areas you can where wiring might get close to metal panels..if its shorting on a panel you'd see a little black mark with a light ring around it. Usually you'd get a smell or smoke though.

Electrical gremlins are the hardest..but at least you know about where to start looking, since you were hearing the sound from about the same area.

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Originally Posted by Lwanmtr

Check the wiring and look for anything that looks burnt. Check all the connectors to make sure they're not loose or have burn marks. also look at any areas you can where wiring might get close to metal panels..if its shorting on a panel you'd see a little black mark with a light ring around it. Usually you'd get a smell or smoke though.

Electrical gremlins are the hardest..but at least you know about where to start looking, since you were hearing the sound from about the same area.

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When you mention it, there was some dirt or soot near the wire, pigtail for the fans. Did not seem like it was melted or anything. But if they were busted, would the fans start when i jumped them over the otterstat?

Were the cooling fans running when you shut the car off? Check the two capacitors in the harness near the fans for damage. Another possible cause may be a fan motor is not bolted tight and you hear it move when it shut off. If the engine was running, maybe the fuel pump also is not tight and it twisted a little when shut off.

Those are good things to check too..hadnt thought of them being loose..and didnt know about the capacitors.

All bypassing the otterstat does is supply power to the fans when the key is turned on, so if they're broke they wont work..if they're coming on, then the fans are most likely ok, unless there is something intermittent.

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Originally Posted by Bitsyncmaster

Were the cooling fans running when you shut the car off? Check the two capacitors in the harness near the fans for damage. Another possible cause may be a fan motor is not bolted tight and you hear it move when it shut off. If the engine was running, maybe the fuel pump also is not tight and it twisted a little when shut off.

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Fans was not running. Suspected the capacitors, but if fans start when otterstat is jumped i guess the capacitors are okay?

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Originally Posted by Lwanmtr

Those are good things to check too..hadnt thought of them being loose..and didnt know about the capacitors.

All bypassing the otterstat does is supply power to the fans when the key is turned on, so if they're broke they wont work..if they're coming on, then the fans are most likely ok, unless there is something intermittent.

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The capacitors are just to reduce electrical noise caused by the fan motors (brushes cause sparks that make electrical noise). I removed my capacitors just to make more noise and test my electronic products. So the caps are not really required for the fans to run.

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Originally Posted by Bitsyncmaster

The capacitors are just to reduce electrical noise caused by the fan motors (brushes cause sparks that make electrical noise). I removed my capacitors just to make more noise and test my electronic products. So the caps are not really required for the fans to run.

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Okay. I will disconnect and measure the capacitors to see if they are okay. I heard it three times, guess the third could be the interior fan. Wonder what made it blow? I have been driving my car in and out of the garage with no trouble before. But would you say the fans should have come on when it hit 228 degrees? Or was I just to wimpy and stopped the engine too early?