72 Eldorado Automatic Level Control

Ant M

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What vehicle(s) do you drive?
1972 Eldorado Convertible Sumatra Green
Hi All. Ant M from Illinois here. I have a Sumatra Green 72 Eldorado Convertible, that I do a little bit more work on each year. This year , my goal is to try and get the ALC to function. All of the parts seem to be in place, compressor up front , no air lines connected, will start out with that. Air lines front to back are in order. Switch on the axle is there. Don't know if it functions. I noticed that one of the last posts was on this subject was a while ago. Has anybody had any success in getting these systems up and running ? Thank you
 

Cadillac Kid 1

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Simple system. The factory service manual is QUITE helpful in diagnosing and repairing these systems. Parts are a bit scarce though and with that quite costly.
Greg Surfas
 

Caddylackn

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Its pretty common for these old relays to get corroded and no longer get good connections, same with the factory grounds. I would start with a voltmeter and see where you are getting voltage to first. Relays can be upgraded, easy fix.

Also remove and clean every ground you can find. You can check grounds by using an ohm meter to test the wires between two different grounds (one should be the one on the frame for the battery if possible). It should be close to zero if they are fully grounded.
 

Schurkey

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Dear Old Dad had a '74 ElDo with the auto leveling system; air-shocks on the rear with a manifold-vacuum-operated compressor up front.

I dicked with it multiple times. Fixed it twice, but the third time I discovered that the "compressor" was seized. That was the end of the auto-leveling. The way I remember it, (it's been decades since I pulled it apart) there was a two-sided piston inside a housing. Manifold vacuum "pulls" the big end of the piston against spring tension. When the piston is at the end of it's travel, the vacuum is switched off, the spring pushes the piston the other way, which builds pressure on the small end to pump the rear up. Then vacuum is re-applied. Sounds like a heartbeat when it worked: QUISSSSS quisssss...QUISSSSS quissss...QUISSSS quissss.

Simple system; typical GM "cost-conscious" design. (i.e., cheap beyond belief.) Of course, GM couldn't use standard air shocks, the OEM units were plumbed differently.

Replaced the leveling valve attached between the frame and rear axle at least once.

Dear Old Dad wasn't sharp enough to figure out that if the bumper dragged going out of the driveway, and other motorists were always flashing their bright lights at him, the self-leveling wasn't working, so it'd be broken for months until I came to visit. That's probably what killed the "compressor"--running constantly, or not running at all.
 
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