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Topic: Dome light, power locks, power mirror, digital speedo all out (Read 2778 times) previous topic - next topic

Dome light, power locks, power mirror, digital speedo all out

85 cougar 5.0. Everything was working fine. Noticed digital speedo back light is on but speedo display and odo are dead (not a bulb issue, can dim and brighten the display but the numbers are not showing up at all in the LCD). Then noticed power locks are dead, as are dome light and power mirrors. Searched threads, checked all fuses under dash and they all test good. Any ideas??  Did not check circuit breakers or any fusible links.

Dome light, power locks, power mirror, digital speedo all out

Reply #1 –
Power windows are a big clue to me, they are only powered through a curcuit breaker and share nothing in common with anything else. I would be looking at the ignition switch. These are known to go bad, and will cause everthing you have wrong, except for maybe the dome light. I did not see a listing for it under any of the fuses or fuse able links. It may be fed off of an always hot wire through the ignition switch.

I'd pull the colum cover off, remove the ignition switch and see what it looks like.
Quote from: jcassity
I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
Hooligans! 
1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
1986 cougar.
lilsammywasapunkrocker@yahoo.com

Dome light, power locks, power mirror, digital speedo all out

Reply #2 –
It's the power locks that are dead, not the Windows. I checked today and fuse 8 is blown and continues to blow immediately when replaced. Any ideas of how and where to look next?
 

Dome light, power locks, power mirror, digital speedo all out

Reply #3 –
Quote from: Bob99b5;456052
It's the power locks that are dead, not the Windows. I checked today and fuse 8 is blown and continues to blow immediately when replaced. Any ideas of how and where to look next?

Lovely, a short to ground.  Have fun looking for it.  Some suggestions - get a wiring diagram and find the closest connector to the fuse, then unplug it.  If the fuse still blows then you have to trace those wires back and find where it's shorting.  If it doesn't blow, pull the fuse, reconnect the wiring harness and move to the next connector.

I had a similar issue a ways back, and it turned out that the harness was rubbing a metal edge where it passed through to the trunk.  I can't recall what fuse was the problem, so I can't say that it/'s the same, but you should try looking for anywhere the harness might be resting near/on sharp edges.

Dome light, power locks, power mirror, digital speedo all out

Reply #4 –
Fuse 8 is a "hot at all times" circuit. It is a Light Green/Yellow wire.
Unfortunately it goes lots of places.
If you have done any work behind the dash, in the center console or inside a door, check there for a pinched wire.

Check under the passenger seat. see if anything has been jammed into the power lock relays.

Check the glove box light.

Check the trunk light and the keyless entry module up behind the rear seat in the trunk.

Dome light, power locks, power mirror, digital speedo all out

Reply #5 –
Quote from: MobileBill23;456058
Lovely, a short to ground.  Have fun looking for it.  Some suggestions - get a wiring diagram and find the closest connector to the fuse, then unplug it.


Thank you, this will not be fun,  I'm sure it's going to be a long process. Does anyone here have a 1985 wiring diagram they can post. I called my dealer today and they only have back to 1989.

Dome light, power locks, power mirror, digital speedo all out

Reply #7 –
Let me narrow it down for you.

Dome light, power locks, power mirror, digital speedo all out

Reply #8 –
And more

Dome light, power locks, power mirror, digital speedo all out

Reply #9 –
Two more

Dome light, power locks, power mirror, digital speedo all out

Reply #10 –
It's FIXED!!!!  But before I tell you what it was I first want to say THANK YOU, THANK YOU, THANK YOU to all of you that offered suggestions of where and how to look, and especially for the links to and jpgs of the wiring diagrams.  I even have to say it again:  THANK YOU.

The problem was the driver side lighted visor vanity mirror.  The wire had a small cut on the side which shorted against the mounting bracket.  One piece of electrical tape, one new fuse, and everything's back to normal.  I also have to say thanks to a wonderful person at Tasca Ford/Lincoln/Mazda in RI where we bought the car brand new in 1985 (they were in Seekonk, MA at the time).  I told him I had isolated the short to circuit 8 with the help of everyone on this board, and he immediately replied via email and said that the frayed visor wires are (I suppose the right verb would be "were" given that there probably aren't many 32 year old Cougars on the road anymore) a common cause of short circuits like this.  Funny thing is I did have the headliner replaced 3 years ago, but I don't think that had anything to do with it.

It all makes sense now.  I lowered the visor when driving to a car show in the late afternoon, and I noticed when we were leaving the show that the speedo and odo were out.  The clock stopped at 7:55pm (which was when we left), so I'm thinking I must have raised/used/moved the visor on the way out and shorted out the circuit.

Long story, I know, but problem solved and hopefully someone will find this handy if they ever search for a similar issue.

Thanks again everyone!

Dome light, power locks, power mirror, digital speedo all out

Reply #11 –
It's great that you got it fixed.

I have learned to Always look for the older guy in the corner at a shop or parts store - they have forgotten more about cars than I will even know!