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eddielines
3rd April 2025, 07:52 AM
C1A20-64 (68) Pressure increases too
slow when filling reservoir - Algorithm
based failure - signal plausibility failure

Hi All

Looking for some feedback

D4 AMK Air Compressor last replaced with genuine about 6 years and 70K km ago

Last week after getting 2 new tyres and driving home I got the above code

I think the timing was co-incidental, I can't see what the tyre shop could have done to cause issues.

I did also replace battery 2 days before this.

To prevent further issues I got it to normal ride height and disabled by putting into build mode with Gap IID.

I understand this can be issues other than compressor such as a leak or bunged up.

In the week since disabling the corners haven't dropped, I think rulling out air bag leak, or hoses and valve outlets to the corners.

I did get this error last year at 2 different times doing water crossings, which I chalked down to a potential wiring issue.

Last year I did open up and there was no breakdown of the beads or powder / gum build up. I didn't have seal kits but the seals looked healthy enough so replaced beads and put back on. Checked again yesterday and beads are good and no powder / gumming.

Did some more testing last night
- using gap iid and service test valves the back and front raised quickly using what's in reservoir, which I think means valve blocks and lines are ok
- enabled compressor, put it down to access mode, then into off road mode, monitoring gap iid, with valves closed, it took over 7 minutes for gallery pressure to rise from about 165 to 240 PSI which I assume is too slow, can anyone confirm. It cut out with fault code again
- I sprayed sudsy water around centre valve block, compressor and reservoir and while it was dark no obvious leaks bubbling
- I disabled compressor while reservoir was open and filling while gallery was at high pressures, over maybe 10 minutes pressure dropped by maybe 6 or 7 psi

To rule out other issues before spending $s on a new compressor what else should I do
- replace seals
- could the front or rear valve be leakeding i.e. just at connection back to central valve block, if corners are not dropping ?
- anything else ?
- pressure sensor replacement ?

DieselLSE
3rd April 2025, 08:47 AM
After 15 years and 180,000km, the compressor has done its job and needs replacing.

veebs
3rd April 2025, 04:58 PM
After 15 years and 180,000km, the compressor has done its job and needs replacing.

Only it was 6 years and 70k km ago - a little early for failure, though not completely unheard of i agree.

DieselLSE
3rd April 2025, 05:33 PM
Only it was 6 years and 70k km ago - a little early for failure, though not completely unheard of i agree.
Oops! Sorry. May be worth cleaning out the valve blocks and lines first.

eddielines
3rd April 2025, 06:15 PM
Do you think I need to look at the front and rear valve block or maybe just the centre one. When I use gap iid and service test valves option, the front and back pop up very quickly it's just the time to build pressure seems to be an issue after I have moved the height once or twice and air in reservoir is lowered.

I know for valves people take them apart and clean and replaced seals, it no sign of sum / powder or decicant break down then I assume airlines are ok, but how do people clean them out ? Compressor ?

eddielines
3rd April 2025, 06:16 PM
I will look at alternator health also due to needing to replace battery, I am guessing low voltage to the pump might also impact its performance ?

Mungus
4th October 2025, 04:43 PM
Sorry had to remove my post as it was related to fill too quick, not fill too slow. [bighmmm]

Globetrotter
4th October 2025, 08:08 PM
I had a similar occurrence although my compressor was a Hitachi. My fault ended up being the output solenoid on the compressor, I fixed it with new seals etc. Now I am not sure whether the AMK has this or not but it is worth having a look especially if you still have the old one.

loanrangie
5th October 2025, 03:46 PM
I would start with a drier service kit and exhaust valve, after 6 years it should still be ok and only require a service.

eddielines
6th October 2025, 10:22 AM
I replaced filter and dryer and o-rings, but ended up replacing compressor and all good. I suspect there was a hairline crack or something and compressor is bdes up getting wet