1990 740 - SRS light on, dash fan not working - intermittent

[DeRail]

Now that you mention it Bill, I know that the key has a significant amount of play in it lengthwise when in the running position, but would this have an effect on the switch itself? I read in the Brickboard FAQ that the 760/960 cylinders can fail, leaving you unable to turn your key and then it has to be drilled. I'm guessing that if I'm able to wiggle the key out like that it's probably time to change it . Do I just go to the dealer and have them code me a new cylinder based on the VIN, or do I have to pull it out and bring it down there?

Will try the key wiggle the next time things start to get wonky.

As for the access to the crash sensor, will I have to remove the drivers seat to gain access to it, or will the seat retract far enough to allow access?

Thanks so much,
Darrell

[billofdurham]

I'm not sure about the lock part of the ignition switch but I would think that, if it failed, you would need to replace it and the keys. The dealer can supply lock kits which include the barrel for the ignition switch.

The electrical portion of the switch has a spring in it that returns the key to the 'run' position. If the spring weakens you can turn the key past its normal 'start' position and that is when electrical problems start. That part of the switch can be found at IPD and FCP.

Very soon you are going to have my whole book!

700 SRS crash sensor1.pdf

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Bill.

[DeRail]

Okay, so this is kind of odd. Today, started the car up, SRS light came on, gave the key some wiggling and the light disappeared (but I can't really tell if it disappeared from the wiggling, as it did take a few seconds, or if it went out on its own volition). However, when I turned the car off and left the key in position 1, the blower motor was working and radio was too, except the vents were stuck in defrost mode, and wiggling the key did nothing. Needless to say, this is very puzzling to me. Classes at university are ending in a couple of weeks, hopefully I'll have more time to dedicate to hammering out these quirks.

Very soon you are going to have my whole book!

Thank you Bill, for taking the time to scan this stuff for us! Don't know what we'd do without it.

Darrell

[DeRail]

Here's an interesting new piece of the puzzle. Started up the car tonight and from the time I started the car to the time I turned it off, the blue light around the A/C button was flashing. Tried wiggling the key around, didn't seem to do anything. Blower was pushing out heat, no problem there, SRS light came on for a few seconds at startup but went out shortly after. Aren't electrical problems fun?

Thanks for the help
Darrell

[billofdurham]

That is not an electrical problem, it is an AC problem. The flashing light tells you that the system has stored fault codes.

760 AC testing.pdf

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Bill.

[DeRail]

That is not an electrical problem, it is an AC problem.

Ah I see. The reason I maybe thought it was electrical is because it's not consistent. Hasn't happened at all since the other night. The weird SRS flickering hasn't happened at all either. The only thing I'm getting now is the light after I start the car for about 5 seconds, then it goes out (before it would never come on other than in position II). What's weird is that there's no belt hooked up to the compressor, so the AC isn't functioning right now.

One thing I noticed today. When I put the key in II, and let the SRS light turn off after its self tests, when I engage the starter, the light comes back on and when the key returns to II, it stays there for about half a second and goes out. I can't remember if it did that before, but does that sound like it could have something to do with the ignition switch? I was thinking of making sure all ground wires in the engine bay are secured, and not corroded (just not sure where all these are). Could this aid in my quest for a bug-free system?

Also, I was thinking about it some more. For awhile, one headlamp has been brighter than the other, don't know if this may point to an electrical problem or not, figured I'd throw it in.

Again, thanks a million
Darrell

[DeRail]

Also, don't know if it lends any help to the problem, but for as long as I can remember, if I have the radio on (on the AM/FM band or on tape, it makes no difference), and I depress the brake pedal activating the brake lights, I can hear a static click. Wasn't sure if this would help pinpoint a ground problem if there was one.

Thanks,
Darrell

[DeRail]

hey guys

sorry for the double post. Im going to crack free and reseat the fuses preventatively and spray them and the sockets with a bit of contact cleaner. Ill also take a look around for ground straps and check those connections. Oddly enough, the issue hasnt happened much lately. I might pre-emptively replace that ignition switch, is it an item worth replacing if I dont know the last time it was changed?

Update: I think it may be the ignition switch after all. Today I started it up and the SRS light was sticking on. I decided to wait a minute... it didn't shut off. But I knocked the key back a little bit and about 7 seconds later or so, it went out. (I also heard my vents moving about) Isn't 7 seconds about the time it takes for the airbag to do its self test when you first move the key to the on position?

Thanks all!

[billofdurham]

It certainly seems like the ignition switch is a major part of your problem.

Bill.

[DeRail]

It certainly seems like the ignition switch is a major part of your problem.

Bill.

Bill, the faulty ignition switch seemed to be the culprit. Swapped it out with a replacement on Saturday, haven't had any SRS or radio issues thus far, hopefully that's the end of that. Next is to tackle putting my drivers power window back on the track.

Thanks again,
Darrell