air con problem

[e12mat]

In the endless quest for a 100% working Tiv, the air con is next.

Had it in the garage yesterday and they removed all of the old gas and did a suction pressure test which turned out ok and then re-gassed with 750g.

The good news is that the air con started working i.e. clutch engaged and cold air inside, so the electronics are working.

whilst monitoring the high and low pressure sides, the high pressure side kept climbing without the low pressure side equalising. At c14 bar the high pressure switch kicked out the compressor.

I'm going to change the receiver dryer, because after initial research it appears as though that should be changed when a re-gas takes place.

In terms of other possibilities I was thinking of the expansion valve?

I was just wondering if anyone has experienced any similar problems?

[ridds]

I thought they did cut out when pressure got to high anyway?

I suffered from a sticky Trinary switch but this prevented the pump clutch from engaging.

[e12mat]

From what I can gather the pressure switch is working because the compressor is being shut down when the pressure gets too high and it didn't work without gas i.e. pressure is too low.

It just seems like there is a blockage in the system, so my thoughts were receiver dryer or expansion valve?

Do the fans switch on when you switch on the air con? Read a bit about condensing units getting to hot whilst no air moving through.

[peaktorque]

If you have a blockage then the system is more likely to cut-out on low pressure. The LP switch is there to prevent the compressor from pulling a vacuum on the low side (which it will do with ease without an LP switch if there was a blockage)

If your system is cutting out on high pressure as you suggest then I would be looking at a possible over charge of refrigerant, blocked/corroded condenser or condenser fan fault (this should start as the pressure reaches the threshold and then stop again as the high side pressure reduces)

Edited by peaktorque on Wednesday 18th April 21:39

[e12mat]

At the moment the compressor is cutting out at about 14 bar according to the garage.

I presume the condenser is in front of the rad, should one of the fans on the rad turn on when the air con is activated? Cause at the moment that doesn't happen.

P.s. both fans work when water temp reaches 95 ish deg

[peaktorque]

e12mat said:

At the moment the compressor is cutting out at about 14 bar according to the garage.

I presume the condenser is in front of the rad, should one of the fans on the rad turn on when the air con is activated? Cause at the moment that doesn't happen.

P.s. both fans work when water temp reaches 95 ish deg

Yes it is a bit of a pig to access on these. Make sure it's clear of leaves and stuff and the fins aren't corroded/missing.

The fan won't operate until the fan switch has been activated by the high pressure gas. As the temperature of the gas increases so does the pressure. You will find that there should two pressure switches on the smaller pipe going to the condensor, one is the safety switch for the compressor, the other will operate the fan when the gas pressure (relative to the temperature) increases. The small pipe leading from the condensor to the expansion valve should only ever get warm, if it gets too hot to touch then you have excessive heat/pressure on the HP side.

Does the A/C work when blasting along an A road? As the fan isn't required when you have airflow through the condenser - good heat exchange.

[Ireland]

14 bar sounds a bit low for a HP switch to be cutting off.

I'd be suspecting that it could be on its way out, worth checking the manual to see what pressure it should cut out at but I'd reckon it should be over 20 bar.

Is the gas circulating at all?

[peaktorque]

20

14 bar is bang on for R134a HP. It should be running at half that with external temps as they currently are.

The fact that it is getting anywhere close to 14 bar at this time of year would suggest a problem with the condensor fans.

[e12mat]

When you say condensor fans, are these seperate to the two big radiator fans?

I think a road blast with air con on is the next step as that should identify if the lack of air flow through the condensor is causing the compressor to kick off.

[peaktorque]

On Cerbs I think the rad fans are the condensor fan. IIRC

If it stays cold whilst on the move then 100% its these fans that are the problem; or I should say the switching of them.

[ridds]

peaktorque said:

20

14 bar is bang on for R134a HP. It should be running at half that with external temps as they currently are.

The fact that it is getting anywhere close to 14 bar at this time of year would suggest a problem with the condensor fans.

These are the pressures for the Trinary switch I've just been supplied by Racing Green for R134A.

Male R134a trinary high & low pressure switch,

Function	Off or Open	On or Close	Off or Open	On or Close
Low Pressure Switch	28 PSIG	29 PSIG	1.93 Bar	1.99 Bar
Fan Switch	185 PSIG	227 PSIG	12.7 Bar	15.6 Bar
High Pressure Switch	454 PSIG	396 PSIG	31.3 Bar	25.4 Bar

Edited by ridds on Sunday 22 April 21:18

[ridds]

I just need to work out which wires are what on the car now.

Old trinary switch wiring does not match and no gas in the system.

[e12mat]

Ridds you are a legend that's exactly the kind of info we need.

Right, so now I know it's definitely not the high pressure switch which is kicking out the compressor.

Took the car for a spin tonight and the aircon is 100% cold, I know it sounds stupid but all the test work has been done in the garage not on the road so I didn't realise how cool the air actually was.

I'm going to get the multimeter out and start testing at the receiver drier and the thermostat.

[peaktorque]

ridds said:

These are the pressures for the Trinary switch I've just been supplied by Racing Green for R134A.

Male R134a trinary high & low pressure switch,

Function	On or Open	Off or Close	On or Open	Off or Close
Low Pressure Switch	28 PSIG	29 PSIG	1.93 Bar	1.99 Bar
Fan	227 PSIG	185 PSIG	15.6 Bar	12.7 Bar
High Pressure Switch	454 PSIG	369 PSIG	31.3 Bar	25.4 Bar

Well I stand corrected (my defence is that I don't do car AC, well maybe a couple of recharges here and there as favours )

Those rated pressures are frightening TBH and far exceed any MWP tests we have to carry out in the commercial AC field I work in. We pressure test up to 285 PSI for R134a on all equipment from a tiny fridge - upwards.

Another example of automotive A/C doing its own thing outside industry guidelines

Edited by peaktorque on Thursday 19th April 20:34