So one of my trucks has decided that every now and them it will fully inflate its rear air bags to the max. Nothing works to deflate. Manual override wont work, unit controller wont either. What could be wrong.
Can’t really help out with that I’m afraid but the same thing happens occasionally with the Actros I drive; if I manually lift or drop the suspension it will not no matter what I try go back to normal ride height until I’ve driven a mile or so. As I say it doesn’t happen every time, perhaps once a fortnight or so.
Pierce a hole in your airbag.
I had a Volvo which did the same thing quite often. It was almost always one or other of the electro pneumatic ecas valves that was faulty. New valve only answer. They are around £300 from the factors. I think the Renault uses the same valve.
It will be intermittent to begin with, then one day will die completely. Does it happen more with an empty trailer and or with solo unit?
Could be a faulty level valve
I drove an FH that did the same thing, started off as an intermittent fault, then failed to go to ride height completely.
They replaced the ride height valve, sensor, gizmo, basically the bit on the chassis that has a link rod to the axle that detects the ride height, never been a problem since.
Found my thread on the subject.
Dont know about the Renault but the Actros tractor units used to do it quite often.
The way to get them down was to disconnect one of the plugs onto one of the rear crucifix sensors on the chassis,turn off the ignition then back on,Because the suspension ECU “saw” a fault(no signal from sensor) it reset itself to default which is back to standard ride height.Then you reconnected the plug and the suspension was fine.Usually happened when the tractor was pulled out from under a trailer too quick.The air bags didnt get time to deflate through the suspension control valve and pushed the crucifix sensors over their parameter limits and they locked out.The ECU cant accept a signal outside its parameters but if you fool it into thinking its got a fault it resets its self to the default.Hope this helps.