97 Mountaineer Lamp Issue

[whatsonfire]

I have a 97 Mountaineer / 5.0L V8

I was driving yesterday afternoon and the dash and tail lamps were working fine. I start up the truck last night and the dash and tail lamps no longer work. My Mountaineer has the autolamps on, so it should detect low light and turn the lights on. It seems the cruise control lamp is not on either, but cruise works fine. The headlights work fine in autolamp and manually.

I tried:
1. Turning autolamp off and turning the headlight switch on.
2. Leaving autolamp on and turning the headlight switch on.
3. Checked the autolamp 20A fuse in the engine compartment.
4. Checked the Illumination switches (7.5A) fuse in the drivers side compartment.

Headlights and break lights work fine. Not sure what other fuses would control this issue. Any help would be greatly appreciated!

 

[whatsonfire]

I've now looked at every fuse I can think of. I checked the 60A fuse and even replaced it just in case. Nothing seems to help. Can anyone provide some guidance?

 

[bobflood]

Used to be, tailights and dash lights were on the same fuse on many cars. That was so you knew if tailight fuse blew and lights were out.

 

[whatsonfire]

That's a novel concept isn't it? I wish I knew which fuse connects the dash lights to the tail lights. I'm guessing it thinks something was not switched, but the headlights come on.

 

[bobflood]

See if you have a fuse marked for the parking lights or tailights. Headlights are on a completely separate circuit.

 

[whatsonfire]

So I took the truck to have some other issues fixed on it and told them about the tail, dash and licence plate lamps not working. They tested it and all the light work. I get it home and it works for three weeks and then they stop working again. I've checked every fuse and they are all fine. I even tried swapping them around just in case it was blown and I couldn't see it.

Seems like maybe a relay somewhere is stuck open, the question is which one. Anyone have any ideas?

 

[OneLever]

... the dash and tail lamps were working fine. I start up the truck last night and the dash and tail lamps no longer work.

Do the front park lamps still come on when the headlamp switch is placed in PARK or HEAD?

It seems the cruise control lamp is not on either, but cruise works fine.

Are you referring to the cruise control indicator lamp on the dash? Or the cruise control illumination lamp inside the cruise control switch attached to the steering wheel?


Both the park lamp circuit and instrument illumination circuit go through the Park lamp relay which is located in the Relay module. The Relay module is located near the driver's right foot if seated. Below are pictures to help you find the Park lamp relay. Links are provided to higher resolution images.

1. Picture 1: View of the Instrument panel steering column cover plate removed. Note you do not need to remove this plate to access the Relay module. I had it removed for other reasons.

2. Picture 2: Under the steering column facing right.

3. Picture 3 Close up of the Relay module.

4. Picture 4 Relay module with cover removed. The cover is held in place by two tabs; one on the top and the other on the bottom. Mine also had a piece of tape around the box.

The relays shown in picture four listed from the top left to right: Head lamp relay, Anti-theft relay, Park lamp relay, Dimmer relay, Accy delay relay (the large one), Battery saver relay, One touch down relay. I suggest you swap out or replace the Park lamp relay to see if it is the problem.

 

[whatsonfire]

Thank you very much for the information! Is this a standard two pole, single throw relay or is it a specialized one? Are all four top relays the same model? Do you think I could swap the anti-theft with the park lamp relay to see if it works?

The cruise control light is working now. It's just the front marker, dash, tail, and license lamps not working. I'm thinking its 99% for sure that it is the relay.

 

[OneLever]

The small relays are the "micro" single pole double throw (SPDT) type I believe. All of the micro relays in that picture have the same serial number so I expect they are identical. You could swap the Head lamp and Park lamp relays to test since you know the head lamp relay is good. The Head lamp relay is the top left one and the Park lamp relay is the second from top left one. I wouldn't swap the Anti-theft one because the PATS system will shut things down if it isn't working correctly. The amperage and voltage ratings for the relays should be marked on them somewhere.

 

[whatsonfire]

Sweet. Thanks for the advice. Any locking mechanism holding these in or do they pull straight out pretty easy? I am going to give it a shot tonight.

 

[OneLever]

They should pull straight out. Most relays are held in place by friction between the male pins and female slots. Might take a bit of wiggling though since that friction is reasonably high.

 

[whatsonfire]

Thank you very much for all the help! I swapped the headlamp and park lamp relays. To my surprise they both started working fine. Seems like a stuck relay was the cause. I am going to replace the relay even though it is working now.

 

[OneLever]

You're welcome! Because relays are just simple mechanical devices you could possibly shake one to get it to work a few more times. After awhile though no amount of shaking will get it to work so it should just be replaced. Drive to the auto parts store and then pull out the one you're replacing. That way you can take it inside and compare it with the new one for proper size and electrical specifications.

Here are two links to pages describing how relays work:
Link 1
Link 2