'92 Legacy Turbo blowing clock/room fuse

[Overclocked]

Hi everyone, thanks in advance for any help you can provide.

I just purchased a 1992 legacy turbo from a friend. It has been sitting for a year, and now blows "clock/room" fuse in the engine compartment. It did not blow this fuse a year ago, the radio worked fine. My understanding is that this fuse protects all interior lights and the radio.

I have a Fluke multimeter so I am able to test continuity, not just play a guessing game.

I checked all wiring on the radio, and it is correct and not shorting out.

What I found which seems wrong:

There is continuity between the power wire and ground for the MAP and TRUNK lights (not the dome light in the middle) This seems like a cause for the problem, correct?



There is continuity between this green power wire and ground. (Map light)



There is continuity between the two contacts (power/ground for the trunk light)

Any advice would be greatly appreciated. Seems weird that this issue would only arise after the car sat for a year.

[Legacy777]

Welcome.

The common link between those two circuits is the circuit MB-8 (fuse 25) in the engine bay that you mentioned. Those two lights are on that same circuit while the dome light is not on the same circuit.

The following loads are that same circuit:

Radio
Height control unit (for height suspension if equipped)
Spot (map) lights
Fuse box light
Rear light (wagon)
Step lights (if equipped)
Luggage light
Trunk light

I would try narrowing down the issue to one of these lights/devices and their wiring. You can d/l the wiring diagrams from me. I don't have all the wiring diagrams scanned for the 92+ model years, but the 90 MY should give you a good idea of things to troubleshoot further.

http://www.main.experiencetherave.com/s ... agrams.zip

http://www.main.experiencetherave.com/s ... and_Elect/

I'd also suggest checking out this thread.
http://bbs.legacycentral.org/viewtopic.php?f=12&t=14485

[Overclocked]

Hi there,
Thank you for the resources. The "door open indicator" screen on the dashboard does not work either, these wiring diagrams do not mention it. Is it part of the MB-8 circuit?

[Overclocked]

This car is becoming a wiring nightmare. Sunroof doesn't work now (no sound of motor/relay), all interior lights don't work, radio doesn't work, and the "door open indicator" also doesn't work.

[Legacy777]

No, door indicator is on a separate circuit, but it is on the same circuit as the sunroof relay. Check fuse No. 15.

Have you gone through and checked with the multi meter whether every fuse is good? If not, I'd suggest doing that. If it blows again, I'd try and narrow down that circuit to the individual components and see if one has a short.

[Overclocked]

I just checked every fuse for continuity (both inside/engine comp.) and only Number 25 is blown.



This schematic from "1992 Service Bulletins" (Your third link) conflicts with the information you have provided me above.
It includes all of these devices on fuse Number 25:
- trunk light
- dome light
- spot (map) light
- radio
- instrument cluster

This would explain why all of my interior lights don't work, (including dome) and perhaps why my "door open indicator" (instrument cluster?) doesn't work either.

I think I am going to buy a Short/Open Circuit Detector to help with the situation.

[Legacy777]

Subaru is unfortunately notorious for having omissions/errors in their factory manuals, so it's very possible that everything is tied to that fuse 25. If you put a new fuse in does it blow right away?

Either way, you'll need to do some more testing with a multimeter or open/short tester.

[Overclocked]

Yes, a new fuse always blows right away. There is a definite short, I measured continuity between the fuse socket pin and ground.
I have ordered a Power Probe ECT2000 (no affiliation) that I hope will lead me to the short. It injects a signal in the circuit and shows the direction of the short, amongst other things. Cost me 100$ so I hope it helps!

It's possible that a squirrel or something chewed wires while the car was sitting...

[Legacy777]

Ok, let us know what you find out.

I've got a power probe tester, and they're pretty handy.

[Overclocked]

The power probe is pointing towards a short within the dash. This is a likely cause because the previous owner apparently already had the dash out once. Perhaps he pinched a wire during re installation.

This means the dash will have to be removed again.

Not fun.. haaa haa

[Overclocked]

The short was found in the dome light wiring with the help of the power probe. It was pinched under the sunroof bracket above the door. It's been fixed now and the fuse no longer blows.

Severed wire:



Pinched and cut by this metal bracket:

[Overclocked]

On another note, the blower fan works on settings "1,2,3" but not "4". My first inclination was to replace the resistor pack, but "4" is full voltage and should not require any resistance. Is there a relay I should check, or perhaps the switch?

[Legacy777]

Glad to hear you found the short.

I have heard others mention issues with the blower fan not working on 4, but I don't recall what the issue was.

The blower motor relay is up under the dash. Look at figure 63-3

http://www.surrealmirage.com/subaru/fil ... tion03.jpg

You can see some of the relays in these pictures.

http://main.experiencetherave.com/subar ... index.html

[Overclocked]

I picked up a replacement fan speed switch from the junkyard to see if it would fix the problem. It did not.

[Legacy777]

Have you looked into the relay?

[Overclocked]

Thanks for reminding me about that. I went and found the relay today.

I think it's the "smoking gun", because pins 3/4 on the relay are very tarnished and their part of the connector is brown. I cleaned up the contacts to see if that would fix it, but it did not. I will replace this relay and let you know the results.




The schematic shows Pins 3/4 as the switched part of the circuit, so this all makes sense.

[Overclocked]

Resistor pack is looking very rusty as well.

[Overclocked]

The blower fan problem was fixed by reconnecting this blue connector under the steering wheel. I thought it was for diagnostics because it's been unplugged ever since I've owned the car. And, of course I pulled the dash before realizing this.

I also replaced the relay before realizing this, but the original was looking a little burnt so it was a good idea anyways.

[Legacy777]

Good deal! Glad you figured that out. Yeah I remember seeing that blue connector when I took my dash out and it's some sort of ground I believe, but I haven't traced the wiring diagrams to see exactly where it goes.

[Overclocked]

I traced the wiring diagrams when I was researching this. That blue connector is for the highest speed on the blower fan, and nothing else.

[Legacy777]

Interesting! Good to know. Thanks!