I am trying to diagnose what is lowering my SLS. I have replaced both air bags and it still drops both sides within a few hours. How do the height sensors work? if I unplug both of them will the truck ignore them and leave pressure in the system? That way I can determine if it is an air leak or an electrical issue. Or will it lower them immediately?

 

I believe if you unplug the sensors the truck will stay at its current height.
If it lowers while off it is a leak, the height sensors only work when the engine is running.

 

time for a bottle of soapy water and a flashlight

 

What you need to do is have a shop, with a good scanner capiable of reading SLS codes, check for codes.
Both sides dropping is always electrical and the chance of it being a leak are doubtful, if there were a leak, it would only effect one bag not both.

 

What else is involved in the electronics that could go bad besides the sensors? should I just go ahead and replace both sensors? they both look pretty corroded.

 

I unplugged the 4 electrical connections at the compressor (compressor, left and right solenoid, and what I assume is a main power connection). Still lost pressure within an hour or so. I sprayed the connections under the housing with soapy water, no apparent leaks.

What i did notice was very short very quiet bursts of air noise when I applied pressure to the solenoid plug. Also, there is a strange constant percolating/tapping noise coming from the solenoid side of the housing.

 

i also just noticed a similar electrical clicking/tapping noise coming from my ABS modulator (I have the 3 amigos off and on). It goes away when I unplug the top connector. Both the SLS solenoids and the ABS make the noise with the truck off. could this be an ecu issue?

 

The ABS modulator is supposed to be "live" for 10-15 min after shutting the truck off, so that is normal.
It should not go flat over night, 3 days or more, sure, but not overnight and defiantly not after a few hours.
Height sensors or not with the key off it should stay up.
Height sensors unplugged and engine running it can go flat because the pump will not run.

 

If you are loosing air, with all the wiring unplugged from the pump assembly, you have an air leak, who's bags did you install, did you have to change the air connections between the line and the bags?

 

They are Dunlop brand bags from atlantic british. They have a push connector as opposed to the original brass fittings. I sprayed the connections with some soapy water and didn't see any leaks, but it is a very slow leak.

Could it be a physical leak inside the valve block? The connections at the compressor and valve block do not appear to be reacting to the soapy water either.