Electrical Gremlins

[blue71mustang]

Help, I'm having electrical gremlins. I don't normally mind but I have no brake lights and can't keep a 30 amp fuse in the slot for more than 1 pump of the pedal.
I'm posting in 2.3 and 5.0 forums since its not an engine specific problem.

I'm looking for ideas for somewhere to start, maybe someones had a similar experience and can save me some headache and hours with a meter.

Anyhow, heres whats going on.... I noticed about a week ago cruise control wasn't working. I did a KOER test on Friday and got a code for brake lights out. Tested hazards, they are out. Checked fused, blown...replaced with 20 amp to get me brakes and get me home.

Noticed Sat. morning, no brakes, no hazards again. Was on the road to work, so I replaced with 30 amp. Heard it blow as soon as I touched the brake pedal. When I got to work, I pulled both brake bulbs, all looked good. I tried a new 30 amp fuse with no bulbs in the sockets, blew on first pump of pedal.

Now here's my current list of faults

1. I have no horn, but cig lighter on same fuse works, fuse good
2. No interior lights on my convertible. The mirror fell off the window and I had to reattach the mirror. When I plugged it back in, blown fuses. Left unplugged fuse good.
3. No cruise control, no hazards no brake lights. Hazards will work with a fresh fuse but first touch of brake pedal blows fuse. Haven't re-tested for cruise because I can't keep brake lights long enough.
4. Water Temp gauge reads extremely low, never gets over 140-145. I have heat without problems. New thermostat, new coolant temp sensor. I had code for temp sensor, but not repeated after sensor replacement.
5. Voltage gauge intermittently reads low or jitters in place. Sometimes reads 10 volts charging for days at a time. No battery issue though always starts first crank instantly. No low battery crank, all lights nice and bright at night even with low volt charging on gauge.
6. Electric rear quarte windows quit working. Fronts still work but backs are out. Motors rebuilt on both side so I know they work. Quit working at the exact same time. One day they both worked, next day they didn't

I'm thinking the water temp / volt gauge are electrical gremlins rather than actual mechanical problems. They are on same side of the dash and I don't have issues with fuel or oil gauge on other side of pod.

I'm also thinking my brake light problem may be being caused by a steering wheel issue. I have no horn and no cruise and they are on different circuts but both are steering column wired. I do have turn signals though and thats also steering column wired.

The rest I don't know

Any help would truly be aprecciated.

Oh yeah car stats...'93 LX Convertible 4cyl auto 85K miles

Thanks, Shawn

 

[ID89GT]

For the brake light fuse thing, try putting a circuit breaker in there and bust out the multimeter and start searching

 

[blue71mustang]

That's exactly what I was trying to avoid, the hours of searching with a meter. I was hoping with the vast knowledge of the board, maybe somebody had had a similar problem that could give me a likely culprit area to start testing.

I figure I'll start by trying to test cruise control first since horn is also out. I'm guessing a steering wheel wiring short is killing the brake fuse as soon as I touch it.

Unfortunately, I have a lot of work this week and the 'stang will sit for awhile until I get time for testing, which means I'll have to drive my 11mpg excursion for the next couple of weeks. I've got lots of driving to do....thank-god gas has finally come down. I'll be putting 85 miles a day on....a couple of weeks ago that would have cost me $32 a day. I love my 4cyl Mustang!!!

 

[92 LX]

I don't know about your light problem, but I had a problem with my cruise and horn. Changed the clock spring and that did the trick.
Good luck and luk what u find out.

 

[Saleen0679]

can't keep a 30 amp fuse in the slot for more than 1 pump of the pedal.

Heard it blow as soon as I touched the brake pedal.

You should inspect your brake light switch and the wiring around the brake pedal for chafing.

You should NEVER over-fuse. Fuses are already rated for higher than normal operating circuit current. Over-fusing can only lead to more damage.

 

[blue71mustang]

Thanks 92LX, maybe horn and cruise have nothing to do for the brake lights. If I get the brakes fixed and they are still out, I'll give that a shot.

Saleen0679, thanks. I was going to check the brake switch after the steering wheel, but after 92 LX's comment. I may start there first since the cruise and brakes may be entirely unrelated.

I also only tried to overfuse to get the car safely home. I know you should never over fuse, but I'll take a 20 minute ride home overfused vs getting rear ended for no brake lights. Once I got to 30amp blowing first touch of pedal (the same stop, not over multiple days), I didn't hot wire the fuse to get home. Now your talking burned car vs very carefull driving. Once you start blowing a fuse, you should always find out why.

Thanks for the replies,
Shawn

 

[blue71mustang]

Well it turned out the brake light switch was shorting the system. I've changed a couple of these over the years (never in a mustang though) and I've never had one completely short my lights out. Maybe its a ford thing, dunno. I've always just had the lights stop working, not blow fuses.

Anyhow, to test it, I pulled the wiring harness plug off the switch and ran a jumper wire across the harness, ta da, brake lights, no blown fuses. I dropped all the way to a 10amp and turned hazards on too, no blown fuse.

New switch was like $13-$14.00.

Shawn