86 325e keeps burning out #10 fuse

Hi everyone, This is my first post and I've searched for my issue without much success. If it HAS been answered, please forgive my ignorance.I'm the original owner of an 86 325e with under 100k original miles

I keep burning out my #10 fuse on an intermittent basis. When I bring it to my mechanic, he replaces the fuse and it runs...for awhile..until it burns out a day or a week later. Now it happens within days or hours..I'm starting to think he's not the person who can repair this problem

I have been trying to figure out "cause and effect" because the burn outs are intermittent...it can be hours after a new fuse or days. I centered around the fan for obvious reasons thinking the fan motor was the cause...but I deliberately had the fan off, a day or two ago when it burned out. Of course, I lose the tachometer, gas gauge etc. But sometimes, the tachometer will come back on briefly, particularly at startup.

I've run out of replacement fuses to test a theory, but I could have swore the last burn out occurred at the same time I beeped my horn...have no idea if it's related but it makes no sense...the horn's not on that panel. Tonight with #10 burned out, and parked ready to drive that EVERY time I put my foot on the brake, the tachometer came back on. I did this about 5 to 10 times...didn't notice if the gas gauge came back up as well...Once I was driving and used the brake, the tachometer didn't respond anymore. This is the only time I've seen the brake/tach interaction.

Of course the overhead panel is dark (is this called the OBC)...I think I've ruled out the fan...I've tested all the other fuses with a continuity probe and they're all good.

Does any of this make any sense or sound familiar. I'd really appreciate any input before I shell out the $$ for a voltage reader. Electrical BMW repairs are expensive in SF.

Thank much!

OK just thoughts as this is going to be a bitch. Has the car been in a crash and damaged a loom? Are all the loom plugs secure and clean? Earths good all over? Loose electrical part touching earth? Are there genius / brain surgeon repairs that are now acting up? Fuse box been tampered with? Alarm or immobiliser fitted / removed? If items not supposed to be on fuse 10 are acting up then it points to crossed / shorting wire or 'repair'. OK I'm guessing, but it seems a reasonable place to start.





k

Factory radio?

Originally Posted by BMWFatherFigure

OK just thoughts as this is going to be a bitch. Has the car been in a crash and damaged a loom? Are all the loom plugs secure and clean? Earths good all over? Loose electrical part touching earth? Are there genius / brain surgeon repairs that are now acting up? Fuse box been tampered with? Alarm or immobiliser fitted / removed? If items not supposed to be on fuse 10 are acting up then it points to crossed / shorting wire or 'repair'. OK I'm guessing, but it seems a reasonable place to start.





k

No major crashes at all except one yellow light ( I forget which one..may be a check engine light has been lit for two years or so after a minor side accident...mechanic said it was a stuck sensor) No "genius" repairs, 3rd party alarm immobilized for at least 10 years, I did notice that fuse 10 & 23? are supposed to be 7.5 amps and some dimwit put in 15 amp fuses in both sockets. That dimwit could have been me

I'm intrigued by the brake/tach seeming connection. Out of nowhere. I'm going to try to replicate it...I've only seen it that one night.

Stock Radio is off awaiting code which I'm looking for. I think it went default when I pulled the fuses checking for continuity. There's a 3rd party disc changer in the trunk which was added maybe 20 years ago.

Is your E30 a 5speed? If so, check your reverse/backup light switch wires. When those cause a short to ground it will blow fuse 10, causing your blower fan and some of your gauges to stop working. It will also not allow your car to start again after you shut down the engine.

Sounds familiar< # 10 fuse in my 87 325e open twice for no apparent reason also. My reverse lamps were always on when the ignition was in run position. I just removed the bulbs and replace the 7.5 a fuse and it has been holding. Just keep searching for problems , work all relays and fuses in and out of sockets. Check out BMWdiy for electrical schematics. Good Luck

This is for fuse #10 out of the E30 Bentley Manual.



My suggestion would be to buy your own pack of 7.5's and stop going to your mechanic for that.

I would think its the back up lights. The connection is under the shift boot. only wires under there. Their is a 'quicker' release that pulls the apart. (I say quicker because its kinda a pain) Only thing I can think of is something is not plugged in right. Could try unplugging it and wrapping the ends in electrical tape and see if it makes a difference.
Green and purple is the power.

Well it maybe when you have your cluster lights on and then go into reverse its triggering the fuse. I assume your whole cluster goes dead?

The reverse/back up light switch problem is not likely to be found in the shift boot area. You're going to have to get under the car and check the lines that run to the switch on the right side of the transmission. Its not an uncommon problem. My problem was that, somehow, the wires got pinched/crushed between the shift arm and a screw/bolt (ground) in the tunnel. A wrap in electrical tape and a zip tie securing the wires fixed that problem. Sure, if you want to no longer deal with this problem you can disconnect the wires in the shift boot area but then you have no reverse lights. Admittedly, I did just that and I drove around with no reverse lights for a good 6 months until I decided to not be lazy anymore.

Pulling the connector will eliminate one possible cause. I would be inspecting the car loom from the front seats to the tail lights for damage or being pinched.