Air con - References

[Bossworld]

Didn't want to override @mulaz thread so starting another, just in time for the end of summer.

A long story short, my 2004 MR2 started its life with a hardtop.  I attempted to have the air con regassed the day before Ding Day 2017.  It was wonderfully cold all the way down to Wrexham and back, but the following day, the system had emptied itself.

The MR2 condenser, in right-hand drive form at least (88460-17121), is unique to the car and there are no known third-party manufacturers.  A new condenser from Toyota is nigh-on £300.   Regardless of what you may find on Facebook, the Corolla condenser fittings are not in the right place, and the only third-party replacements for the MR2, are for left hand drive.

The MR2's condenser also includes the receiver/drier built in.  The official service manual suggests that this can't be replaced, however, there is a hex plug on the underside of the tube that holds the drier, and I believe this takes a 17mm hex (drain) socket.  The reason I say 'believe' is that the factory one is made of plastic and after many years of cooling cycles and road grot, it will be welded in place.

When I took my old condenser out, in the interests of science I attempted to remove the plug covering the receiver drier and bent the condenser in the process. I was only able to remove the plug via destroying it using a hole saw.

The replacement receiver drier is around £20 online and comes with a new metal plug and two o-rings.  Brand NRF, part number 33187 - https://www.autopartspro.co.uk/nrf-2388370  (other manufacturers are available)

Air-con o-rings are specific to air con use.  They're also one of the common leakage points as they dry out from lack of use - hence why you should keep using air con all year round, even if it's just for demisting in winter.  The Toyota O-rings do not appear to match the sizes offered in the eBay kits and Halfords.  The front pair of o-rings around the condenser connections are around £5 from Toyota for the two.

[Bossworld]

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My current state of play - a local specialist spent a couple of hours with me last May changing the condenser.  He did everything correctly, pulling a vacuum for a long time, evacuating the system, making sure the amount of refrigerant was manually measured etc. I then had air con all last summer through to very early this Spring.

I went for a run out to the Scottish borders on a very rainy day and there was a lot of unavoidable standing water.  The day after I got home, I noticed my air con was no longer cooling.

Couple of days later, I noticed green goop around the upper condenser fitting.  So, after getting the remains of the system discharged, I swapped the two front condenser O-rings for the proper Toyota ones.  You must coat them in PAG oil before you fit them.  The Toyota o-rings were a much snugger fit than what went on before.  At this point, the system is now stock with the exception of a brand new Toyota condenser and the two new Toyota o rings.

I then took the car to Kwik Fit two weeks ago - it held a vacuum fine and they regassed it.  Unfortunately, in that two week period, I have noticed that the car is now short cycling (the air con comes on for around 15 seconds, cuts out, then comes back on.  Repeat ad infinitum and it's not good for wear and tear on the compressor.

They're going to take another look and re-gas it on Wednesday morning but I suspect I've possibly got a leak elsewhere (even though the system can hold a vacuum - I don't believe Kwik Fit's machines that do it all automatically will be holding a vacuum for long enough to prove it either way, you need to pull it for at least 1/2 an hour).  Even then, with the knackered condenser it still held a vacuum - I've since read that it's not the most reliable of tests as the system may pull tight under negative pressure (vacuum test), but give up under positive pressure (i.e. charged and running).

The air con pipes also run around the fuel tank, so if you've had to replace handbrake cables, there's another likely cause of any pipe damage.

I saw a couple of other people comment recently about air con, I appreciate I've had very little luck with this car from the beginning but wondered if anyone else had done any ad-hoc replacement of the system?

[Bossworld]

Urghh

Make of this what you will.  Took the car back down to Kwik Fit, they've left it idling for half an hour and during which time the compressor isn't short cycling, and there's condensate coming out of the pipe quite happily.

The gauges also look fine, been speaking to the Master Tech about it.

I've since done some further research and it seems our compressors don't have a shaft seal, there's a couple of snap rings, so again unless the o-rings have gone on the pipes coming on or off the compressor, or elsewhere in the system, I think the compressor is either going to be working or it isn't, it's unlikely to be the source of the issue.

The lad thinks I've either got an issue with the pressure in the system (which he's just about to empty and re-charge) or there's some kind of ambient temp sensor playing up. I'm only aware of the thermistor in the glovebox area, fitted to the 'cooling unit'.  Don't know whether there's a thermistor fitted to non A/C cars' cooling units too?

So, assuming it does gets charged, I can only assume one or more of:

1) Some kind of water shock/freeze caused the undersized o-ring to fail after my first Borders blast in the pouring rain/full of puddles.
2) More recently, the system was possibly not charged up enough.
3) Or, the thermistor is playing up (don't think it is, as I checked the resistance on it a few weeks back), and/or there's some other kind of ambient temperature check that hasn't kicked in, in the heat/sweat of the car idling in Kwik Fit for 30 mins.  Or, I wonder if the fan connector had water in it and was possibly causing a short (though it worked on/off in 20 seconds increments)

Does anyone know of any other HVAC temperature sensors on our cars?

[Bossworld]

With regards 1 - I think this is correct, and/or the receiver drier somehow got a lot of moisture in it.

With regards 3) and some further reading, I don't believe there are any other temp sensors other than this thermistor.  There is a pressure check but other than that it really is quite a simple system.

Paul@TCB kindly advised that our thermistor is out of production.  Luckily I managed to get one from Amazon.com for about $14 shipped to the UK.

The repair manual suggests it's a simple job to prise the carrier out of the cooler box - maybe it was 15 years ago but not now!  Made quite a mess of it as there are two tabs that lock it in place that are buried down the length.

I put the old, removed resistor in iced and warm water to test it - may be a placebo, the resistance didn't get quite as high on the old one, in comparison to the new, but it wasn't a million miles off the correct figures.

Still, gave me a useful position to test, if you strip the thermistor off the plug and bridge the wires then it seems as though the air con permanently runs (with the button pressed).  Probably not good for the compressor but useful as a test.

Fitted the new one, the air con is still short cycling but I would put that down to the cold weather outside.  Guess we'll know more in the spring.

[shnazzle]

Not sure if this helps but I had aircon woes after my last re-gas. I had it done at Northeast Tyres and Exhausts in Silverlink. That's now a Kwikfit. 

Anyway, took my car to AK Automotive a few back to get my system tested for leaks, as my A/C wasn't working, only to find that it was perfectly sealed but only about half full at best. 

So... Wouldn't trust that particular outfit if they couldn't even fill a system properly.
Might be a similar issue at the place you're taking it?

[Bossworld]

Not sure if this helps but I had aircon woes after my last re-gas. I had it done at Northeast Tyres and Exhausts in Silverlink. That's now a Kwikfit.

Anyway, took my car to AK Automotive a few back to get my system tested for leaks, as my A/C wasn't working, only to find that it was perfectly sealed but only about half full at best.

So... Wouldn't trust that particular outfit if they couldn't even fill a system properly.
Might be a similar issue at the place you're taking it?

I do think the air con o rings were wrong (they seemingly are generic sizes in bulk boxes, which is what my original specialist used) and the Toyota spec is wildly different to the generic ones.

Unfortunately most of my troubleshooting came late in the season - the car ran with the air con on without issue in the heat of Kwik Fit's garage and I trust what the specialist they had come down to redo it, said.

It's a rock and a hard place as I've spent too much money and time on it, for it not to be perfect. But my only other reference point is a 7 year newer car with climate control.

Current state of play is that it gets icey cold but the compressor clicks back off, then on again within about 30 seconds. May be innocuous but I won't really know for sure until it's 20 degrees outside again. I've also now got that dummy thermistor I can use to override the temp check, and see if it's anything else daft like a faulty fan.

Glad you got sorted, make sure you keep using it over winter