Thread: Compressor Issue?

Drier desiccant starting to break down possibly, no dash messages or error codes ?

Originally Posted by loanrangie

Drier desiccant starting to break down possibly, no dash messages or error codes ?

no codes and it's a Hitachi compressor

Originally Posted by rocket rod

Recently I changed all struts and all worked well at this stage. Just noticed now at starting the car my compressor runs for a few seconds, stops, then runs a few seconds again etc, etc and after while settles down.

This is for a late D3, but all the info I've seen indicates the D4 is similar but maybe with slightly different pressures :

If you have no leaks and don't drop height it should run once every start*, and twice every couple of starts* (2-3 in my experience).

* Where a "start" is after the vehicle being stopped and idle for some indeterminate amount of time I've not been able to accurately pin down (>5 mins and less than an hour).

After months of observation the algorithm "appears" to work like this.
Start car.
Pressurise gallery from reservoir to measure pressure (open reservoir valve, wait until pressure stabilises and close reservoir valve). Note if pressure is above ~16.(5-7) bar absolute.
Vent gallery to ~2bar.
Start compressor and wait until gallery > ~10bar. Stop compressor
Vent gallery to ~2bar.

If initial pressure measurement was < 16.(5-7) bar then :
Start compressor
Open reservoir valve and wait until gallery > 17.7 bar absolute
Stop compressor
Close reservoir valve
Vent gallery to ~2bar.

2 or 3 pressure tests is enough to drop the reservoir below the 16.x threshold and make it pump up. It runs every start and pumps the gallery up > 10 bar as a compressor test.

If I run into the shops, generally it doesn't re-do the test on a warm start.

Originally Posted by rocket rod

no codes and it's a Hitachi compressor

Are you sure its a hitachi ?, all D4's from 2012 ish should be AMK.

Originally Posted by loanrangie

Are you sure its a hitachi ?, all D4's from 2012 ish should be AMK.

Looked at compressor type in the GP tool and it said it was Hitachi. That's all I was going on. Haven't had a look though.

Originally Posted by BradC

This is for a late D3, but all the info I've seen indicates the D4 is similar but maybe with slightly different pressures :

If you have no leaks and don't drop height it should run once every start*, and twice every couple of starts* (2-3 in my experience).

* Where a "start" is after the vehicle being stopped and idle for some indeterminate amount of time I've not been able to accurately pin down (>5 mins and less than an hour).

After months of observation the algorithm "appears" to work like this.
Start car.
Pressurise gallery from reservoir to measure pressure (open reservoir valve, wait until pressure stabilises and close reservoir valve). Note if pressure is above ~16.(5-7) bar absolute.
Vent gallery to ~2bar.
Start compressor and wait until gallery > ~10bar. Stop compressor
Vent gallery to ~2bar.

If initial pressure measurement was < 16.(5-7) bar then :
Start compressor
Open reservoir valve and wait until gallery > 17.7 bar absolute
Stop compressor
Close reservoir valve
Vent gallery to ~2bar.

2 or 3 pressure tests is enough to drop the reservoir below the 16.x threshold and make it pump up. It runs every start and pumps the gallery up > 10 bar as a compressor test.

If I run into the shops, generally it doesn't re-do the test on a warm start.

That is how my my12 D4 behaved,but I don’t know what pressures it cycled at.

I have a MY 07 Disco 3 with Hitachi compressor and it does the same thing on start up. Exhausting then running the compressor, then exhausting and running the compressor. I never noticed it until I changed my compressor and removed the sound deadening in the compressor housing. I thought it was a fault with the compressor. Seems like a crazy function to drop the air and run the compressor on every start up all that needless work the compressor performs.

Originally Posted by PTCAAR

I have a MY 07 Disco 3 with Hitachi compressor and it does the same thing on start up. Exhausting then running the compressor, then exhausting and running the compressor. I never noticed it until I changed my compressor and removed the sound deadening in the compressor housing. I thought it was a fault with the compressor. Seems like a crazy function to drop the air and run the compressor on every start up all that needless work the compressor performs.

Depends on your point of view I suppose. Is it better for the car to tell you “sorry there is a problem with the suspension” when you leave the driveway, or would you rather find out when you beach it and it can’t extend?