HVAC - AC not blowing ice cold.

strummagnet · #1 11th May 2023, 01:33 PM

Hi. I should have noticed this before, weather not being warm enough, but my HVAC unit or the AC bit is not blowing ice cold.

I have:

Checked fuses - no issues
Run a scan on the HVAC unit - No codes present
Visual inspection - all seems good - no loose connections

Cycled through the options, switching ECON on or off does not not seem to indicate any changes to the compressor. I checked the compressor fuse (drivers footwell) and that is OK. Are there any other connections I should be looking at?

Saff · #2 11th May 2023, 02:46 PM

Hi Paul
If the compressor is not kicking in and the fuse is ok then my VERY limited understanding suggests either the gas is low/flat or I seem to remember if the cooling fans aren't working then the compressor won't run. Hope that's some help. Steve

MikkiJayne · #3 11th May 2023, 03:03 PM

Is the compressor spinning?
Is the electric fan on?
Is it cooling at all?
Condensation on the pipes past the header tank?
Is the centre vent switching between hot and cold?

If it'll switch ECON on/off then the HVAC unit thinks there is enough gas, which comes from the pressure switch on the evaporator.

Its becoming increasingly common for the valve blocks to fail and allow hot water through constantly, meaning even if the AC is running ice cold, you still get a face full of hot air. Marcel and I are working on a solution for this which is not tested yet.

steamship · #4 11th May 2023, 05:54 PM

Quote:

Originally Posted by strummagnet

Run a scan on the HVAC unit - No codes present

I'm sure there was somewhere in the measuring blocks where it gave the refrigerant pressure value, but can't find it. Something similar to this video from the 22 second mark:

https://youtu.be/H9wJNAJBcvI?t=22

Turns out, if I switch my ECON off, the engine stalls. I'm hoping that this is because there is no gas in the system (after having the front off), and it just needs pressure tested and regassed, and not issues with the compressor.

MikkiJayne · #5 11th May 2023, 06:53 PM

Quote:

Originally Posted by steamship

Turns out, if I switch my ECON off, the engine stalls.

This is bad and means the compressor is locked up or is about to undergo rapid unscheduled disassembly. There's nothing electrical which could cause that, and the engine doesn't care if there's gas or not. In fact, that implies there is gas since the hvac wouldn't try and engage the clutch if there wasn't. See if you can turn the inner portion of the pulley by hand - it should spin freely with the engine off. I suspect it won't move, so when the clutch engages its putting an untenable load on the engine at idle and stalling it.

I would suggest pulling the compressor fuse (S8 in ST3) until you can get it replaced as what you definitely don't want is the internals exploding and going through the rest of the system. That gets messy and needs the dash out.

There are Hella replacements on ebay for £180 iirc, or thereabouts. I've used a bunch of them and they seem to work well. Its simple to DIY as well - just get it discharged, its about an hour's work to swap even on axle stands, and then recharge.

David's8 · #6 11th May 2023, 07:29 PM

Wasnt "rapid unscheduled disassembly" the term used to describe Mr Musk's latest attempt to get get a rocket into space which resulted in ..... an explosion of several hundred tonnes of oxygen and fuel mix?

Now, MJ usually calls a spade a spade so when she uses a PR spokespersons reality-avoiding terminology it must be REALLY serious

MikkiJayne · #7 11th May 2023, 07:48 PM

Its been a term in rocketry for many years. I think the earliest documented usage is in the 60s referring to the Saturn 5 engine development when one of the engines dismantled its test stand. SpaceX just brought it to public attention recently by making a really, really big explosion this time

Ronin · #8 14th May 2023, 07:31 PM

What about the green AC compressor clutch plug located on the passenger side lower bumper area? I unplugged mine recently as my compressor also is on the verge of seizing, I will be having it changed soon.

tintin · #9 15th May 2023, 02:45 PM

My S8 behaved similarly a few weeks back (on its first long run out for a while....). Couldn't get it to blow cold on any setting, though it did get slightly less "hot" after about 20 minutes.

However, on a subsequent drive about a week later it was much closer to normal, if not ice cold...

strummagnet · #10 16th May 2023, 05:34 PM

Quote:

Originally Posted by MikkiJayne

Is the compressor spinning?
Is the electric fan on?
Is it cooling at all?
Condensation on the pipes past the header tank?
Is the centre vent switching between hot and cold?

If it'll switch ECON on/off then the HVAC unit thinks there is enough gas, which comes from the pressure switch on the evaporator.

Its becoming increasingly common for the valve blocks to fail and allow hot water through constantly, meaning even if the AC is running ice cold, you still get a face full of hot air. Marcel and I are working on a solution for this which is not tested yet.

Is the electric fan on? Yes, running fine.
Is it cooling at all? Not cooling at all, fan on high speed.
Condensation on the pipes past the header tank? No condensation, pipes appear to be warm to touch.
Is the centre vent switching between hot and cold? No discernible difference when switching from warm to cold on centre vent.

Am I looking at Valve block replacement or finding a learned AC person?