ELC-3 year mystery finally solved!

[Loekee75]

To everyone who has Electronic Level Control (ELC) I finally got the time to really researched the system schematics to find out just why the system failed on me a few years ago. It worked when I first got the car, except it would keep running after the vehicle was shut off so long that it would totally drain the battery! Well, as it turns out, that battery was very old at the time and couldn't hold a charge very long without the engine running. All that time I blamed the ELC system, assuming that the relay was at fault (or maybe even the level sensor) After replacing the battery with a new one, I disconnected the ELC compressor under the hood, because frankly at the time I had no idea what that compressor was, nor did I know what "ELC" was in the fuse block! The ride maintained its comfortable, plush feel and I never reconnected the compressor again for another 3 years. After I joined the Forums, I soon found out what ELC was and I immediately began working on my car's system as soon as I got a long time off work a couple of weeks ago. When I reconnected the compressor and started the car, the system did not come on. I did all the regular system checks, fuse, directed voltage to compressor, and both checked out. Not knowing that the system comes on when the vehicle shuts off to exhaust, I still thought the relay was at fault, and perhaps was the reason the system was not working at all now. I tried replacing the relay with the same kind, but that plan did not work. For a while I started pointing fingers at the level sensor. And it was scary imagine trying to get a new one (check out the price at GM Parts Direct) or crawing under another PA at the boneyard in the mud. Before "assuming" any further, I spent a good hour on my back under the dash with my voltmeter and my '92 electrical manual, testing all 4 of the relay prongs I was getting readings from everything with the ignition on, but prong #2 was not getting grounded (a shed of light when I added a jumper wire to ground here and the system came on, music to my ears! ) But where did this lead lead to? It was a yellow wire that went back to the level sensor. Again, bad level sensor? I went a little further and checked the yellow wire for continuity, starting at the level sensor connector and all the way up to the relay connector. The voltmeter beeped, indicating the wire was not broken. This started getting on my nerves, because so far all of the tests were pointing at a faulty level sensor. I'm desperate at this time, and I test the yellow wire coming straight from the sensor, and get nothing. Something wrong internally inside the level sensor? I looked again, and this time I unwrapped the 16 year old electrical tape and conduit from the level sensor harness. I actually started laughing when I saw that the yellow wire had a 1/8 in. tear in the insulation and green looking wire underneath! This means that the wire was damaged some time while I had the system disconnected, and the fact that I thought the system wasn't supposed to come on after the vehicle was off REALLY threw me off! South Texas weather is relentless on wiring , I guess. I cut and spliced the wire, wrapped it up with more electrical tape and recovered the whole thing with conduit. Now my ELC finally works as it should (well, I found out that the air bladders are shot, but hey, at least all I need now is a new set of shocks, and I'll be ready to go!) And to think I almost went and bought another level sensor and relay. This whole story was a very good lesson for me, I learned more about ELC than I ever thought I would, and more importantly, I learned so much from researching those wiring diagrams, that I know it'll help me to tackle more electrical problems in the future. I posted this for anyone who is having ELC trouble, and maybe my findings are somewhat alike with yours and you may know more what to look for.

[TopherS]

Nice work

I remember when I had my Roadmaster, that the ELC system wasn't working correctly (it had leaky shocks and the system is ALWAYS on, even when the car was off, so as the shocks leaked, the compressor would cycle on/off to keep it level, every 10-15 minutes or so, 24/7). Luckily, I had a good battery, so never ran dead in the 2 years I had the car (w/ the shocks leaking the whole time). Not knowing anything about the system at all made it very intimidating to even think about investigating the problem. It was much easier to close my eyes and pretend it wasn't there. Now, we have a place to refer to for some good info.

It would be a good thing to know if the system has changed from certain years to others...for instance, as I said, my 95 Roadmaster had (optional) ELC and it was active at all times, on or off. My 2001 Park Avenue (ELC is Standard Equipment) will only level itself after the car is turned on, but will exhaust even after the car is turned off. I don't know if all Park Avenues are the same as my Park Avenue...or...if certain years were designed as my Roadmaster was (active at all times). This would help some people to know exactly how their system is supposed to function and when. (Sounds like this would have helped alleviate some of your frustrations, too).

Thanks for sharing your hard work. Happy Thanksgiving.

[HotZ28]

Thanks Tom for the detailed post on your ALC findings. Most of the time, it just takes persistence and good troubleshooting techniques to find the problem.