Paranoia - electrical fire?

When I bought my 1990 coupe, I had a lock issue in the pass side door. I made a new part so the lock linkage connected to the piston again, and was happy with my work. Later that day, I took it to a restaurant and locked it for the first time with the door panel button. When I came back to it 40 minutes later, it was filled with smoke. I ended up having to amputate the wiring for the lock back below the driver side seat and remove some damaged wiring that killed the pass side courtesy lights too. The fuse melted but the wiring into the fuse box didn't burn. It hasn't shorted out again, but I haven't rebuilt the harness either.

My fear is reoccurrance. My driver side lock is slow. Is there a chance that this could happen again? What would cause this? I'm afraid to let it sit, even unlocked. Should I be worried, or was the fire caused by the lock position sensor being off because I bent the linkage? If it is a danger, is there a way to prevent it without cutting wires or losing other functions?

The big unknown is the history before you purchased the car. I do not recall anyone having a "fire" problem among the posts here.

The previous owner may have disconnected the lock because he had a problem and could not find the source. If you do not own a service manual, there is one at www.reatta.net and you can trace the wiring.

Good luck

Only thing I can think of is a hot wire got cut/pinched. Have not seen that happen before. Also sounds like the wire saved the fuse. What size was it and which one ? Perhaps a PO had it blow before so put in a bigger one.

It had a 10A fuse. The only thing I could not get straight was why it behaved that way, drawing so heavily after I walked away. Is this not something these cars can do? Does the lock try to fire again after it is shut off? There's a small off Chance I was sitting on the key fob because I didn't know it worked until months later.

Where was the damaged wiring found? Sounds like it was under the driver's seat not in the door. I suspect that is where the short was. Many of the splices in the wires under that seat are hot all the time and problems with them are pretty common.

There is no position sensor involved. The power to the motors runs thru a circuit breaker rated at 30 amps. Plenty to fry wires before it would blow. Might be a problem with the door lock relay which controls the flow of the 30 amps.

There is a circuit breaker in the locking motor which should have prevented this problem if the problem was in the door. So I expect an issue with the relay or a switch keeping the relay closed, and the splice under the seat was the weak point that caused the wire there to melt the insulation.

Is this not something these cars can do?

In almost 10 years of posting here, this is a first!

So, no, it's not something these cars do.

John F.

In almost 10 years of posting here, this is a first!

So, no, it's not something these cars do.

John F.

Au contraire, it is something these cars are quite capable of due to several circuits that are fed by fuseable links and highly rated circuit breakers. Luckily, failures are rare but not unheard of. Don't you recall posts about the 80s headlight switches and wiring harness going up in smoke? Same issue, just a different circuit.

McR,

I was speaking to the issue of a problem with the door specifically.

John F.

It burned from the door wiring back through the harness under the seat. Is this a problem I should be concerned about happening again? It didn't happen until I used the pass side lock, and hasn't happened since.

If you want to hook the passenger's door lock motor back up you need to figure out what the problem is or it could happen again. This assumes the driver's side is still working. Same would apply to it too if it isn't.

The driver side works fine. For my purposes I don't really need electric locks anyway, should I disable the driver side or should I assume if it hasn't happened in the 2 years I've owned it it wont? The thought process being the problem was in the lock harness to the pass side door only?

The part I can't figure out is why it happened after I hooked up the pass side locks mechanically. The wiring was always hooked up, I just had to hook the linkage back up. Then it burned. The piston had been firing the entire time, but once I put it under load it burned up. The drivers side works all right, should I assume by removing the damaged wiring I am safe?

It would seem from what you describe, the problem was with the pass locking motor. When put under load it pulled too much current thru the wire from the splice under the drivers seat melting the insulation. There is a circuit breaker built into the motor that should have shut it down before this happened, but for some reason didn't. Also, the flow of current to these motors should only occur for a short time when a switch is momentarily pushed, and the relay activated allowing the high current supply to flow. So two things had to happen to cause this to come about. A switch had to remain closed to hold the relay closed, (or the relay had to stick in a closed position), and the circuit breaker had to fail inside the locking motor preventing it from shutting it down. The door switches, key FOB, and relay are common to both sides, and are still working properly since you have no problems with the driver's side, so I believe the problem was just with the motor in the passenger's door. The motor in the driver's door probably shut down on its own as it's supposed to when the relay stayed closed, so no problem occurred there. If no other problems with the door switches or key FOB have been noted, I believe the pass door motor was the major culprit, and while hard to believe, butt dialing of the FOB may have contributed the other part of the equation.

If there is no other reason for that relay to have stayed closed, then replacing the wire and the door locking motor should repair this situation safely.

Thank you. I really appreciate your help and advice. You all are very knowledgeable and I'm glad to have such people helping me on this project

There are a few guys here that you should take there word for...

That would be Mc_Reatta, Padgett, Drtidmore, and kdirk. All are highly knowledgable in electronics. Sorry if I slighted anyone else.

May as well chime in here. I think MC has covered it pretty well. I would only add the possibility of a chafed wire shorting somewhere in the line. Most likely in the door near moving parts, though most of the mechanical linkage for the lock actuator is well guarded.

I think the 1990 cars have the hold to unlock feature (I know 1991 does) where there is a ring contact attached to the rear of the outside lock cylinders. When you turn the key to unlock and hold it there for a couple of seconds, it will unlock all doors (just the two on a Reatta, but many GM sedans also had this feature). Equivalent feature to the double tap on the unlock button of the key fob (drivers door unlock on first press, both on second). So, there is a possibility of this contact and its lead wire being at fault also. I've seen the wiring for this get chewed up by a slim jim, so I'd not rule out the possibility.

May also check the power lock switches in each door panel. I've seen these go bad, perhaps one stuck in lock and the failsafe in the passenger motor failed to trip causing an overdraw that melted wires.

I almost have to think this was a compound failure - more than one thing went wrong concurrently - to cause this kind of damage without blowing a fuse or breaker.

These types of incidents are quite troublesome. It is difficult to be confident the problem is ever 100% fixed unless a definitive cause can be established. Personally, I'd probably replace every possible component that may have been at fault in such an instance. That would be as close as I could get to being sure it was repaired with no likelyhood of recurrence. I don't ever want to come back to my car after being parked a while and find an ash heap.

I hope you can come up with a satifactory answer. You are rightly concerned about this, as I would be in the same circumstance.

KDirk

Right now I've got the fuse pulled. I almost want to rewire the courtesy light on that side and disable the leads to the locks. The passenger side is disconnected already, so it would be simple. I would bet it was the sensor on the lock cylinder in the door that trips when the key turns. That and a lock motor that was unhooked for a reason. Thanks guys. I love my Reatta and couldn't bear to see it burn, so I've been worried.

PD,

If you don't already, It might be a good time to start carring a fire extinguisher in your car.

I'm not being facetious or trying to be a smart-Alec. I have one in my truck. Probably should throw one in my car too.

John F.

Hey guys, I was digging through the archives looking for something else and noticed something. Someone else reported this problem, but he caught it sooner. Remember how I said the courtesy lights cooked too? He found it was a courtesy light wire shorted out. I think it's reasonable to call that the cause, seeing how I didn't check the courtesy light wires in the door when I reassembled it.

A possibility, but the lock motor wire has to come into play too. The courtesy light is powered all the time. The locking motor is grounded most of the time only going hot when commanded on. So look for where the courtesy light wire could have shorted to the lock motor wire in the door or under the seat.

If you are still worried about fire, you could always install a battery cut off switch for when you are not driving the Reatta. Kind of a PIA, but, no juice, no electrical fire.