1993 Mercury Grand Marquis Air Bag Module

[Arquemann]

Thermal resistor might be the single black thing in the middle of the board. Thermal fuses look kinda like resistors, so it's hard to say from that. Dunno if there should only be one or multiple...

[friskyfrankie]

Thermal resistor might be the single black thing in the middle of the board. Thermal fuses look kinda like resistors, so it's hard to say from that. Dunno if there should only be one or multiple...

Thanks bro - I'll take a more careful look. I assume you mean the black round item in the middle? According to a YOUTUBE video, there is only one thermal fuse and resistor. They just look vastly different from what I have in front of me hence the confusion. I'd just like to find them and see if I can repair it to keep as a spare as new ones are extremely if not impossible to find. That is assuming the caps are good - they look ok but need to test them for sure. The new unit, so far, is working well so I'll look into it when I can. By the way, wonder what the black and white thing on the board is?

[Arquemann]

Disclaimer: I don't know much about electronics.
But this:

Looks like this:

Thermal fuses look like normal resistors, there's quite a few of resistor looking things on that board. But they are easy to check, just check continuity from one side to another. It's a fuse so it should be ok or blown. You could check resistance through them, I believe a thermal fuse should not have much resistance like normal resistors do.

[friskyfrankie]

Excellent info - thanks!!

[sly]

Nope... the black and white plastic case has a resistor and the 10A thermal fuse. (I think it's 140C, but I'll have to look that up again).

Sorry, it's been a BUSY week around here.

[sly]

172C
Found a video showing how to fix it:

[friskyfrankie]

172C
Found a video showing how to fix it:

That's the same video I've seen but my "guts" look different as per my photo. I'll still try to figure this thing out. By the way, I greatly appreciate your help so no need to apologize - busy is busy!

[VicCrownVic]

According to this guy:

The black and white thing is the thermal resistor. I believe the internals of the black and white thermal resistor are the same as the 2 resistors the guy in the other video Sly posted.

Edit: LOL, finished watching the video, it is the same thing just in that black and white case.

[friskyfrankie]

Wish the video was not fuzzy but you can certainly make it all out. He had a Code 51 where mine was Code 52 (which I think are the caps but I need to verify). Still need to check each component but this definitely helps - so many thanks!!

[sly]

Yeah... the 4 large can shaped caps on the edge are the "backup battery". Doesn't really matter what version of that blue box you have, they all work the same basic way.

[friskyfrankie]

Yeah... the 4 large can shaped caps on the edge are the "backup battery". Doesn't really matter what version of that blue box you have, they all work the same basic way.

Difficult to get a straight answer (on the Internet - not here) but if I remember correctly, Code 52 points to defective caps. Maybe someone can verify?

[sly]

Yes, typically. Sometimes it's cold solder joints on the pins to the connector or broken/corroded traces on the board. One module I pulled from a junkyard to diagnose my system with had corrosion on the board under some caps. I used it for the diag and found out the real issues eventually and swapped back to the original one after replacing the fuse. Then made a dummy out of the junkyard module (resistor between 12V and airbag light) that only lasted about 2 weeks before the resistor failed (most probable issue - not a large enough resistor). I didn't feel like making a "smart" enough circuit to really function properly (omnifet and a few complimentary components). But anyhoo. Having repaired that module a few times... I don't know if I actually have the dummy in the car or the OG module with a blown fuse... I know more than the average bear about the stupid thing.

[friskyfrankie]

I'll be checking for corroded/faulty solder points in addition to caps, fuse etc. Have several doctor appointments next week but hope to get to it soon. So far, the replacement module is not throwing any codes so I hope to repair the old one to use as a spare.