Fuse #8 on 1991 SHO blows intermittently

[shomanbob]

The #8 fuse (15 amp) on my SHO blows intermittently (can't tie it into any particular activity, like turning on the radio or opening or closing a door,or going over a bump, etc). My owner's manual lists the following protected by Fuse #8):
Chime for keys in ignition
Clock
Keyless entry system
Radio memory
Lights for engine compartment, glove box, instrument panel, interior, power mirror,trunk or storage area.
I suspect there are also other functions that also are on the fuse #8 circuit but I don't have any wiring that will tell me what.
Can anyone furnish this info?
Any hints as to what might be causing my fuse #8 to blow?
Thanks

 

[SHOhopefull]

I need to throw a big X2 on that one. My '90 does the exact same thing... The last 2 fuses snapped as soon as the metal touched. I can't put a radio in till I get this resolved.

 

[1MadSHO95]

Check your headlight switch for a melted connector. If it is, replace switch and connector. Also, check all your door ajar switches for pinched or chaffed wires.

 

[shomanbob]

As far as I can see the headlight switch and door switches and wiring look OK. Anybody have any other ideas?
Where could I get a listing of all circuits that tie into the #8 fuse?
Thanks

 

[firebat45]

When mine did this it was the connector for the rear left door. The contacts had backed out of the connector housing and were shorting together.

I think it fubared something up with the keyless because my car only unlocks the driver door now, but you can hear all 4 door motors go. Plus it does it on the first click of the remote/as soon as you enter the code.

EDIT - It blew the fuse randomly a couple times, then started blowing it every time a new fuse was put in.

 

[shoon]

Exact same thing happened to me. Check how much voltage is coming out of the alternator with engine running.
The regulator in my alternator was fried, so it was overcharging my battery a bit. 15.5 - 16 volts.

the keyless entry module doesn't like the extra voltage, there is a metal oxide varsitor (electronic component soldered onto circuit board inside of keyless module; used to control voltage spikes) but if given high enough voltage for long enough they short out... so try unplugging the keyless entry module in the trunk and replacing the fuse again.

 

[shomanbob]

Thanks for the responses. I plan to check out these possibilities. Can you give me more specifics as to where I go in the truck to unplug the keyless entry module?

 

[32sho]

The service manual shows the power antenna , clock, dimming rheostat,radio, power mirrors switch,left door jam switch (on base models without keyless entry) and glove box lamp switch. I would disconnect the three most likely which i would think are the power antenna, dimming switch and left door jam switch. See if it stops blowing the fuse. Then connect one at a time and see which one is causing your short. If you have keyless entry it could be any of the door jam switches.

 

[shoon]

Thanks for the responses. I plan to check out these possibilities. Can you give me more specifics as to where I go in the truck to unplug the keyless entry module?

Drivers side, behind the back seat in the trunk. It's a little black box with lots of wires going into it.