Within the last 6 months, I have replaced my alternator and all the gearing systems, all of my spark plugs, and my radiator/cooling system, yet something is still draining the battery. Every month or so the battery dies and takes 5-10 minutes to successfully jump start the car (no lights come on at all). However, I hooked it up to a battery charger and charged it to a full charge then ran my car and measured all the voltage differences from different areas which all seemed to be correct. I am wondering if there is another place that I am not thinking of that could be draining the battery. Last night I had it parked for 45 minutes to come back to a completely dead car, but it started on the first try this morning right away and ran great.
My car has 230000 miles.
My car has a manual transmission.
It is possible to have a bad ground or short somewhere. Check the connection at the negative battery cable to the engine/chassis. Remove, clean, and reinstall it. Also check for loose connections/ground at the fuse box.
I owned a Jetta of the same generation - 85-92. A common source of trouble is the fuse box under the drivers side dash getting wet. A common source of water intrusion is around the windshield seal as well as a clogged cowl drain under hood. It can fill with water and come through the firewall through the speedometer cable and other things running through the firewall.
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