Need hep- blown fuse #8

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Need hep- blown fuse #8

March 01, 2008, 11:23:11 AM

Working on a '85 T-bird 30th Anniversary special. the car sat for 6+ years with bad motor, I'm trying to resurrect it. It's running now, but I'm having problems with fuse #8. With no associated electronic work, the fuse started blowing. chased around behind the dash, couldn't find any problems- took the radio out, headlight swith out, unplugged the following: PW switch & relays, pwr mirror switch, pwr locks, and key/door buzzer. Fuse still blew (instantly when plugged in- like dead short) Let car sit 1 week (had to buy more fuses!), replace fuse- no problem. Installed everything- radio, all connections from above--- still good (for 1 week). Blew again after opening trunk- found trunk light on same circuit. unplugged trunk light (and under hood also- just in-case)- no problems for 1 month plus! Now it just blew again after a hard right turn. I know it sounds like a bad wire somewhere, but I'm hoping someone as a better idea than to disassemble the whole car looking!

Also, the car has full digital dash. when the fuse blows, I loose speedo and trip minder on the dash (tach/gauges still function), radio memory, interior lights, mirrors, pwr locks (not sure what else).

Please Help! I'm going crazy!

Need hep- blown fuse #8

Reply #1 – March 01, 2008, 12:16:48 PM

see attached.

Start by installing a circuit breaker type fuse. IT will reset when it cools down.

Turn on your radio to an am station with tunes / talk radio ect.

take a look at the fuse 8 circuit designations and start doing a wiggle test on all sub systems / harness's listed. Your biggest problem here is the fact the fuse is no longer blowing instantly. This might make the troubleshooting a little harder. Setting your radio to AM will help alot on intermittant problems.

I would start with the illuminated entry harness cause its harness could be rubbing the linkages along the door handle and its a real tight fit up in that area for wiriing anyway. this would also include the door lock circuit.

Your just listen for pops and cracks on your radio as you move each harness along its installed path. Hopefully that circuit will blow the CB while you are fiddling around.

good luck.,, but dont keep wasting fuses when you probably have a circuit breaker you can swap in its place. If you dont think your exising circuit breaker will work, just use a couple of thin blades to stuff up in the fuse 8 socket then gator clip to each side of your circuit breaker.

Need hep- blown fuse #8

Reply #2 – March 01, 2008, 06:31:22 PM

Sorry I didn't get back to you earlier- I was in the shop changing the fuel tank, pump, and cleaning the sending unit--- I have a functional gas gauge again!

I haven't tried listening on AM, but there is no difference for the radio on FM. the fuse only controls the memory. I think I understand your point on AM--- the minor power flux might show up in the speakers anyways- I'll give it a try if I can get the circuit to work again.

As it is right now- the CB (yea, already went that route after 2 packs of fuses) breaks the circuit after 20 seconds of being installed (sounds like I'm back to a dead short). it does it with doors open, closed, radio on/off, key on/off--- short story- ALL THE TIME! the only way I fixed it last time was to let the car sit for a week (yea, not a real fix obviously, but I didn't do anything and it started working fine). This brings up another question--- what device would give up after having power on for a couple weeks, but reset if you kept the fuse out for a week?

I've used the online wiring diagrams, and even pages from the evtm, but neither shows the whole story on the circuit. the evtm (actual wire diagram) doesn't show anything about the circuit going to the radio memory and I can't find how it connects to the cluster memory (which I'm guessing is why the speedo blanks out).

It's just frustrating--- rebuilt my first motor 25+ yrs ago, worked engines, trans, electrics, bodywork... never had anything beat me up like this! Thanks for any help I can get!

Need hep- blown fuse #8

Reply #3 – March 01, 2008, 07:42:00 PM

was this happening before you stopped driving it?

Need hep- blown fuse #8

Reply #4 – March 01, 2008, 08:06:18 PM

no... car sat for 6 yrs with burned piston... no electrical problems, no fuse problems until about 4 months after driving it again.

after fixing motor, had to clear out all kinds of animal leftovers (grass, fur, twigs--- either small birds or field mice) from the AC plenum and air intake area. fixed a few chewed wires under hood area, but all interior wiring was untouched. No electrical problems or electrical work done prior to this fuse problem. Nothing done to fix this problem- but it "fixed itself"?? when it sat without power for a week.

Need hep- blown fuse #8

Reply #5 – March 01, 2008, 08:27:55 PM

Mabe another bare wire grounding out somewhere. the sitting for a week could just be a coincidence.
or mabe a relay heating up and grounding out somehow.
Just throwing out ideas to you

edit: Did you check the wires going to the doors for damage

Need hep- blown fuse #8

Reply #6 – March 01, 2008, 11:41:25 PM

yep, checked door wires// wiggled all available harnesses (within reason- haven't pulled the carpet out!). I agree that the sitting for a week is probably a coincidence, but I thought maybe somebody has seen this before with one of the elctronic units (hoping to short-cut the problem with somebody else's experience!)--- has anyone heard of the electronic dash causing any of this?
Still looking at all the wires. I'm getting tired of chasing this light green/yellow wire around the car- but I'll have to keep going.

Need hep- blown fuse #8

Reply #7 – March 02, 2008, 12:28:25 AM

the wiring harness to my radio used to fritz out and cause a loud tone through the speakers, other than that I've never had any problems with wiring In my car to solve.
The grounding out theory is all I have to offer.
mabe a mouse got under the carpet somehow.
one got in my car somehow and made a nest behind the back seat where the speakers are mounted

Need hep- blown fuse #8

Reply #8 – March 02, 2008, 01:16:42 AM

ok
Not sure if you have the whole EVTM but like said,,,, Unhook your associated relays to the circuits and also, uplug the harness to each door.

retest and check with us.

fuse.

Reply #9 – March 02, 2008, 01:32:00 AM

may be silly but you should check all wiring in trunk you can get to tail lights, trunk light,brake ligths ect. sounds like a mouse problem to me. chew on a wire just enough to ground out under certian conditions. and pull rear seats to follow more wiring.

keep your post up so we know whats happening.

Need hep- blown fuse #8

Reply #10 – March 02, 2008, 10:56:59 AM

It's working again???

I started at the fuse block, following the lt green/yellow. found it split right off the fuse block, one of them went through a connector (with about 11 other wires)- figured it would be a good way to split the circuit in half. after disconnecting the plug, checked with the c/b--- circuit worked- dash/radio memory, mirrors, locks, lights... don't know where the other wire went to, but I couldn't find anything that didn't work (trunk/hood lights still unplugged, so not sure on them). I wanted to get an idea on current pull, so I plugged in a 7.5A fuse- fuse didn't blow--- low current is good! Went back and plugged the connector in, 7.5A fuse still in and working. Apparently the car just wants me to unplug/replug various connectors once a month! I'll let you know if the problem comes back.

---EDIT----
All the above is true, couldn't duplicate the issue in the garage no matter how many cables I moved, pulled, wiggled. Had the fuse in for approx 2.5 hrs (2 hours in garage--- interior lights working, tried all the accesories) with about 20 min drive time (just over 20 miles on the interstate), when the speedo up and disapeared due to another blown fuse- put the c/b back in, and just constantly resets. I was traveling straight on a calm interstate (no rough action, no potholes) when the fuse blew... It's back to always poping the c/b sitting still. Still chasing around...

Need hep- blown fuse #8

Reply #11 – March 03, 2008, 10:22:55 AM

do you have the complete evtm?

you shouldnt have to be manually tracing out that lead. the evtm shows where each connector / splice is located.

Need hep- blown fuse #8

Reply #12 – March 05, 2008, 06:21:40 PM

I don't have the full evtm--- I have pages that have been pulled from here for the wiring / lights. I would love to have the full evtm, but don't know where to find one or what a reasonable price is.

also- haven't had time to do anything with the car... hopefully I'll get back out to it later tonight or tomorrow night...

Need hep- blown fuse #8

Reply #13 – March 07, 2008, 12:24:12 AM

Quote from: brisomm;207825

I don't have the full evtm--- I have pages that have been pulled from here for the wiring / lights. I would love to have the full evtm, but don't know where to find one or what a reasonable price is.

also- haven't had time to do anything with the car... hopefully I'll get back out to it later tonight or tomorrow night...

ill burn you a copy to cd,, just pm with mail to addy.
it will be for 87.

Need hep- blown fuse #8

Reply #14 – March 12, 2008, 11:09:24 PM

Well, chased wires around again... cut one wire that I don't know where it goes (previously unplugged trunk and hood light, so it could be the long run to get to them...) has worked for 2 days now- about 60 miles drive distance- to work and back... everything that worked before works now... keeping fingers crossed!