Thread: D4 A/C Compressor issue

Originally Posted by haydent

Here is a screenshot of my ac pressure from car off, to start car with ac on full.

Screenshot_20221231-103201_IIDControl.jpg

Looks fine after the 4 minute mark,but cycling at just over 3000Kpa before that doesn't seem correct?

But then again last time i played with auto air the systems had a glass and ran on R12.

See what the others think.You may have another fault that caused the compressor failure.
What were the ambient temps at the time?

Not sure, but when I had it regassed and first started running it the tech said the pressure was a high and asked if it had a thermo fan, i said i thought there was put not sure where. then it kicked in and the pressure became normal, so likely its just this, that the thermo fan hadnt started running yet, i can do another capture with this plotted too.

That graph is a bit disturbing. I'd much prefer to see a set of gauges to work out what is actually happening.

Originally Posted by scarry

Looks fine after the 4 minute mark,but cycling at just over 3000Kpa before that doesn't seem correct?

The manual says "Increases to 33 ± 1 bar (479 ± 14.5 lbf/in 2 ): the ATCM loads the A/C compressor again when the pressure
decreases to 23.5 ± 1 bar (341 ± 14.5 lbf/in 2 )." So looks like it's oscillating on the protective limiter.

I've *never* seen a SCT of >80C even under the worst ambient conditions.

Originally Posted by BradC

The manual says "Increases to 33 ± 1 bar (479 ± 14.5 lbf/in 2 ): the ATCM loads the A/C compressor again when the pressure
decreases to 23.5 ± 1 bar (341 ± 14.5 lbf/in 2 )." So looks like it's oscillating on the protective limiter.

I've *never* seen a SCT of >80C even under the worst ambient conditions.

As i thought,cycling on the HP switch.

With 2.7l D4 i could see the revs the fan was doing on the Gap tool,but i am not familiar with the set up on the 3.0L,that is if it is a 3.0L.
But something is not correct,probably with the fan,air over the condenser is too low,at a guess.It isn't coming on at start when it should be.
We set our safeties for R404a/R22/448,etc, at 400PSI,run around 280PSI,depending on ambient,and this is 134a

I wonder if thats how long it takes the viscous fan to speed up from dead cold?

It starts off normal, slowly ramps up due to no cooling then slowly comes back down. How long does it take the ECM to heat up the fan and get it moving.. Especially at idle.

Go for a drive with this log on, include fan command, I'll log mine the same this morning and report back.. It doesn't good.. But it might not be that bad.

Ok, just tested my D4.

On start up the fan was running at 1000rpm.. So basically 1:1. Never went past idle.. Pressures started at 140psi and creeped to 170psi but never any higher..I had the knobs on full cold with the windows down.

You can do it again watching fan speed or get a hose on mist and cool down the condenser at the same time. Also log other things, my air con saved list on gap has evap temp. Ambient. Pressure valve current etc.

Start with the fan

Here I was thinking it was a separate thermo fan turning on a minute or so after startup, but it must be the viscous ramping up.
I ran the test again (everything cold) and this time pressure didnt go so high, much more stable, will try again another day. Maybe this time due to ambient temp being a bit lower. Engine is TDV8

edit: (this graph is a bit off, car was only idled, so fan rpm is wrong and viscous control is not changing, yet fan speed is)

Screenshot_20230101-190927_IIDControl.jpg