Hey guys I was wondering if anyone could shed some light on my AC issues.

I've owned my ls430 for a few years now and it's never had working AC. The condenser was shot to crap so it was the obvious issue, I replaced it easy enough.

​​​​​I had the system vac tested and gassed up on Friday. I drove home and the AC was nice and cold. Today (Sunday) I went shopping which is a 20 minute drive, again Ac was nice and cold. Did my shopping and on the way home the AC didn't work at all, it just blew ambient.

I got home and had a little nose about, the AC clutch engages as it should, switching AC on/off engages and disengages the clutch. Still ambient air.

​​​​Changing target air temp on display does nothing.

Things worth noting:
There is a cable/solenoid activated coolant valve on the bulkhead in the engine bay for the heater matrix. This disintegrated a month ago and I've temporarily replaced it with a 90degree joiner, this means engine coolant isn't being cut off when heat isn't needed.

Also the rear AC system has been removed and the pipes blocked off in the engine bay.

The only thing I can think of has something to do with the coolant valve missing. I've driven the car 3 separate times, twice with a cold engine (and therefore heater matrix) the AC worked. But the time the engine and matrix were hot it didn't work.

Perhaps a sensor at the matrix is seeing all that heat and it's causing the AC to not engage? But the compressor is running at that time??!?!

I dunno, I'm hoping someone can shed some light on this.

Cheers

 

Try bypassing your heater core and see if that fixes the problem for now. It sounds like you are reheating your conditioned air. Also check your AC sight glass while the system is running to make sure the refrigerant is full and flowing.

 

Yeah I was thinking of bypassing the matrix completely to see what happens, not as if I need heat atm!

I did think I might be reheating the air but why would it have worked previously and not now?

Will check the sight glass tomorrow 😊

 

Without gauges, you could run the a/c for a couple minutes then feel the piping related to the system. One pipe should be cold, the other hot indicating that heat is being transferred.

i would also install a ball valve going to the heater, so you could restrict the flow of hot coolant during the summertime.

 

Just got home, at work I blocked off the heater pipes. No change.

Got home and had a look inside the sight glass, there is little movement in there but can't see much happening tbh.

Again clutch engages fine

I've ran the AC on for 20 mins, felt both pipes near the bulkhead and they're both hot

 

are you sure the a/c clutch is staying engaged the whole time?

sounds to me that you are low/empty on refrigerant and if so the low pressure switch should cut power to the a/c clutch to prevent damage to the compressor.

you really need a set of gauges, or at least one of those DIY a/c charge bottles with the built in gauge so you could at least see what the low side pressure is.

 

The evaporator is not visible in any way, correct? Just relating it to a house/central AC, and a refrigerator/freezer. I would expect the evaporator to be iced up if refrigerant has leaked out...

 

The evaporator is inside the HVAC box, so you won't see it. The low pressure switch should kill the power to the A/C clutch long before it ices up.

Really need to check the hi/low pressures or at least as mentioned get a can of refrigerant with the built in gauge to see what your low side pressure is.