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Re: Old, New 750iL (long) (archive)

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Posted by Tracy Evans on August 12, 2001 at 14:41:01:

In Reply to: Re: Old, New 750iL (long) posted by Wayne McKay on August 12, 2001 at 13:03:52:

Thanks for the comments. Especially with regard to the headrest, instrument panel and lights. I will look into that..


Sounds like you are on the right track but will add a couple of things to shorten your efforts.

1) in your model year the lighting fault detection (except headlights) are handled by a separate relay we affectionately call the "Mustard" relay due to its colour. It is located in the fuse box and this is the one that usually requires the resoldering. Failing that, it is usually poor connection in the contacts that triggers the relay to complain. There are some great sites and archives on this one.

2) the instrument panel problem sounds very typical of failing capacitors in the circuit board. Again some great sites and archives on the fix for this one.

3) recent posts (last week?) and the archives on the headrest should help a lot if you can hear it trying to activate. If not, there is a switch in the seat belt connector that triggers auto up/down feature. If the head rest dow not function at all, you will likely have to start with the wiring in the switch behind the plastic panel to check for power, etc. and trace your way through until you find the problem. My Bentley is at the office, but if you have one you can look through the electrical diagrams to identify fuses and relays that you need to check as well.

4) can't help with the fluid level but would agree that the level sensor would be the first place to look. Have you done the proper level checking routine as layed out in the Bentley?

5) the SEM switch itself can be a problem due to its easy access to spilled Coke and coffee. If things do not clear up, try removing and cleaning.

6) agree on the O2 sensor comment except that you have so few miles on them...I don't think time should cause them to fail. The best way to check is to measure their output with a digital volt meter. Again previous posts in the archives discuss this quite well.

As for the archives, I find the search capabilities to be very inadequate so I wouldn't be suprised to see some of your questions arise again. See what you can find and repost with what you feel you are missing. You will get lots of help.

'88 750iL

P.S. I would have dug out some for you in this post but I am getting the evil eye to get on with some household fix ups I have promised to do for a little too long now.

So a month ago I bought a 1989 750iL with only 18,000 miles on it. It was one owner, miles are documented.. it sat a lot. I got a good deal on it and it's a gorgeous car. I've put about 1500 miles on it since and am just begining to understand my new toy..

The car runs well, it's fast and comfortable, but it has a few issues. Here they are:

Seems like everything works, exept for the power headrest on the drivers side in the back seat.

I get a message of "POW STEER FLUID" on the computer about half the time I start (or shutdown for that matter). Fluid is not low, found a bad sensor on the hydraulic regulator (it was leaking), replaced it and bled the system according to my bently book. I've noticed the two serpentine belts are cracked and losing chunks, goes in tomorrow to have them replaced, but I'm leary of this fixing my problem. I'll not that the steering doesn't really feel quite right when cold and at low speeds, but it's hard to describe, feels fine at speed.

Had "Trans Program Error" on hot days, them my SEM switch didn't work. This was always temporary. I think I've nailed this one, buy unplugging and reseating all the relays and connectors I could find. There was some minor oxidation on the contacts. But the problem has not returned and I've had a lot of hot days since then.

Backing off the gas during high speed (70-80mph) jaunts will cause the check engine light to flicker.

Driving at night with the lights on, I periodically get a message about a Parking Light Failure, though I don't find any lights out. I've reseated the LKM to no avail. I did, once, find my left rear tail light out, but tapping on it brought it back. I've reseated all the bulbs and connectors associated with it that I can find in the trunk.

When I start the car in the morning, and it always starts right up, for about 30 seconds, the temp and gas gauges show nothing and the computer display is blank. Then it 'pops' and everything works.. At least as far as I can tell.. Some times I notice flickering on the LED display. This only occurs in the morning, no other time during the day.

So there's my list.. I consider the power steering the issue needing to be addressed first. My plan is after the belts, if the problem is still there, as I suspect it will be, is to replace the all the fluid (pentozin chf 7.1, this car has the LAD system). Maybe look at that switch in the resevoir. Though I don't reacall seeing that in my Bently. I should note that if I just turn the car on, but not start the engine, I will still get the low fluid message, but I cannot find any fault codes in the computer using the 'stomp on the gas 5 times in 5 seconds' method mention in Bently. (any recommendations on a decent fault code reader, Peake?).. Maybe test the pump pressure, but I'm looking for ideas..

As for the Transmission and Parking lights issue, I'm thinking a fluid and filter change is probably in order for the transmission. And I think I need to break out my soldering iron and touch up joints in the LKM (or whatever it's called).

Check engine light flicker is probably an O2 sensor complaining.

And the odd dash activity may be more soldering..

So I'm looking for comments. Anyone have any ideas on any of the areas I'm diving into, please let me know if you think I'm doing the right things or if I'm missing something. This will be greatly appreciated...



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