Legacy electric problem

[Guest rpalmer47]

Have a 90 Legacy, driving along, all of a sudden no Air Cond., no power windows, no heater fan, no tach or gauges, except speedo, which is cable driven.

All fuses under the hood, and under the dash check out fine. Battery is fully charged, and Alt. is working.

Car runs and drives, radio, wipers, headlites and turn sigs. all work normal.

 

Any ideas??

[Guest Legacy777]

hmmm.....that is a doozy of an electrical gremlin.

 

unfortunately it'll probably be quite a pain to track this down. I'm honestly not sure what all those things have in common.

 

How long does this last....a few seconds, minutes, days?

 

Does it happen when going over bumps, or just going down the road?

 

The speedo is mechanical up to the meter, then it is electrical. I would assume if the car keeps running the ECU and other componants related to the car's operation are still functioning.

[Guest theotherskip]

check the grounds under the dash. loosen all of them (that you can find), clean the metal surfaces under them, then reattach them. that seems to be the common link...

[Guest lmdew]

check and clean all the ground wires. There are several in the engine area. Sounds like you might have a bad ground. Good Luck!

[Guest rpalmer47]

This problem is permanent, not intermittent. I thought it would be easy and obvious to find, but have spent 5 or 6 hours of checking, and re-checking connectors, voltage, etc.

 

I have tested the main power wires that go from the engine fuse box thru to the underdash fusebox, as well as the ignition switch. All appear fine, and there is voltage to under the dash.

 

With so many things failing at the same time,

it does appear to be a ground fault, but so far haven't found one. I loosened and retightened a couple grounds under the hood yesterday, so I guess I will look for some under the dash today. A wiring diagram would be helpful. I did find one for an Impreza.

www.ravensblade-impreza.c...iagram.pdf

[Guest theotherskip]

pull the fuse for the instrument panel. check for continunity to ground - if you get a real low ohms (around 1ohm or less), then you have a wiring fault. then you just have to trace the wiring. check all the places where it can get cut - around metal parts, through the firewall, etc. but basically, you are in for quite the fun time. there aren't really any easy ways to track this down...

[Guest meep424]

thats a power bus, not gnd prob. Likely to be in the ign switch itself-- note that all those items shut off in the start position. I think the power goes through the switch, not a relay. BUT I'm not positive (pun). relay would be an easier fix, but I'm pretty sure it's the switch.

 

mike

[Guest rpalmer47]

Problem solved. Maybe!

 

How can this be? I had checked all the major fuses and connectors, except that I didn't pull the little 10 amp fuse for the instrument cluster from the fusebox under the dash. When I pulled that little sucker to check the resistance to ground, I discovered it was blown!

When I inserted a good 10 amper in that slot, all the problems went away, and the car works normally.

How can one little fuse take out so many electrical circuits?

 

I then pulled the new fuse, and all the problems came back. Reinserted it, and they went away.

 

Is it possible that I still may may have a ground problem, and that all the circuits that didn't work are now finding ground thru that little fuse? Those circuits were the Air Cond., power windows and sunroof, heater fan, and the tach & gauges, except speedo.

 

If anyone out there has a similar Legacy, and wants to pull the 10 amp instrument fuse located under the dash, bottom left corner. to see if all those problems occur, it would be a major lesson for me.

 

I am just a little afraid that the original cause is not fixed, so the little fuse is carrying too much ground current, and may blow again.

 

Many thanks for all the suggestions from the posters who replied. As a backyard mechanic I have often had success solving car problems with feedback from forums like this one.

[Guest Legacy777]

probably just the fuse. Just keep an eye on things and if it comes back, you may have a short.

 

If you had a ground problem, it would most likely still be there, regardless of the fuse, and it sounds like you've checked quite a few things and didn't see anything out of the ordinary.

[Guest Legacy777]

what fuse number was the fuse you replaced?

[Guest rpalmer47]

I replaced fuse # 15.

Prior to that I had cleaned up most ground connections in the engine area, under the hood, so maybe I had already fixed the cause of the blown fuse. The main connection to the battery negative terminal was pretty ugly; ie lots of white powdery corrosion crap.

I'm still a little confused how one little fuse could take out so many circuits.

If anyone wants to try to replicate the problems on a '90 Legacy, by pulling fuse # 15 under the dash, I would be interested to know if all those problems do occur. It won't destroy anything, as far as I know.

Once again, thanks for the support. I'm happy the car is working normally again. These forums are great!

[Guest Caboobaroo]

watch for your grounds cause if they loosen up, the circut will pull too much amperage and it will blow your fuses. If they become loose or corroded, this problem will happen to any car. I know cause I had it happen a couple of times to one of my Camaros

[AK_Ghost]

Am chasing this problem currently. 1990 Legacy blows fuse #15, taking out power windows, tach-gauges, AC, and seatbelt. Problem pops up every couple of weeks. Have repalced the fuse multiple times now with no identified common cause. I think I have found/checked all the grounds and connectors along this circuit, but haven't found a good wiring diagram to be sure. Wiring resistance reads normal, and wires apear in good shape. Any suggestions?

[lmdew]

I had a Loyale that was doing the same thing. Found a wire melted up in the wire run behind the dash. Look at the back of the fuse box for signs of over heated wires. If you find them, trace them back to the source of the problem. The 6' wire was melted in several locations and in contact with other wire cores.

[sregor13]

"All fuses under the hood, and under the dash check out fine. "

 

Does that include the Fusible Links. If yes then how did you test the links? Also have you done any electrical work in your Car. Car Stereo or anything? Even if no then there could a be a Ground Fault in you Head Unit. Maybe, anyway just an idea. Thanks