Prado 90 A/C issue

[campertaylor Lurker Find all posts View Profile Close campertaylor]

Hi Guys,
Just after some assistance. The A /C on my 90 runs for about an hour, then the cold air stops. The compressor clutch engages. But no cold air.
I've just had it regassed, but the the filtered was not changed, the A/C guy didn't think it was necessary. I hadn't had it regassed for about 5 years, it had been working fine.
I have replaced the fan switch resistor.
I have checked the relay(heater/ A/C in the box under the bonnet.(I'm not sure if there are more under the dash).
I have taken the glove box out to earth the thermistor on the evaporator ,it gets cold again. The amplifier seems to be operating.
I was thinking maybe Tx valve or thermistor on the Evap.
I'd appreciate any assistance.
Cheers
Les

[Steve M Addicted PP Member Find all posts View Profile Close Steve M]

Not freezing up is it ?? If the Evap (behind glovebox) freezes up it will not let the air flow through. Thermistors are cheap so might be the place to start. Seems funny it's just started doing it after a regas. Are you saying no air flow out vents or there is air flow but not cold ??. TX mmm maybe but never heard of them playing up in the 90's. Sounds like a blockage of some sort. But to be honest, for this aircon guy to do a regas and not replace the filter I'd be questioning his work ethic. Should have replaced the filter, vacced it out, put in amount of gas by weight, with a dye in it (usually green) to check for any leaks if needed down the track. There was a question asked a while ago not sure of the exact symptoms but turned out it was running a tad low on gas and was freezing up but if you still have air flow out the vents then it's not freezing up....

[JKAF Junior Member Find all posts View Profile Close JKAF]

I was getting a strange problem with my A/C that would start cooling and then warmup.
It turns out the cable to the heater seems to be getting tight.
This stops the knob from going all the way to max cold or when it does it then slowly goes back a bit.
It ends up with some hot water getting through and heating up the cold air.
Fix so far has been to squirt some WD40 into the cable to loosen it up but still a bit tight.

[scottkz Senior Member Find all posts View Profile Close scottkz]

When its gone warm and suposed to be cold get out and check if the compressor is running... if its still running i would first look at the thermistor

[topic97 Senior Member Find all posts View Profile Close topic97]

If it shuts down & your compressor clutch is still engaged, it wont be your thermistor/thermostat that's causing the drama - all they realistically do is regulate the temperature by shutting the compressor on & off - which if its still engaged and you have no cold air it wont be the thermistor/thermostat.

I've been out of the industry for a few years, so I cant quite remember which system the 90 series uses (TX/Drier or Orrifice/Accumulator), but next time it shuts down, if the compressor clutch is still engaged, locate where the pipes go into your firewall.
Put your hand on the fat pipe & check the temperature - if its warm, it will be your TX/Orrifice that's malfunctioning & causing the system to shut down, but if its cold, the issue is elsewhere.

Its a bit hard to diagnose without getting the head pressure readings, but if you have any dramas, any competent a/c workshop should be able to pinpoint the troubles.

[scottkz Senior Member Find all posts View Profile Close scottkz]

If it shuts down & your compressor clutch is still engaged, it wont be your thermistor/thermostat that's causing the drama - all they realistically do is regulate the temperature by shutting the compressor on & off - which if its still engaged and you have no cold air it wont be the thermistor/thermostat.

I've been out of the industry for a few years, so I cant quite remember which system the 90 series uses (TX/Drier or Orrifice/Accumulator), but next time it shuts down, if the compressor clutch is still engaged, locate where the pipes go into your firewall.
Put your hand on the fat pipe & check the temperature - if its warm, it will be your TX/Orrifice that's malfunctioning & causing the system to shut down, but if its cold, the issue is elsewhere.

Its a bit hard to diagnose without getting the head pressure readings, but if you have any dramas, any competent a/c workshop should be able to pinpoint the troubles.

I can tell you now that my thermistor failed/not connected witch caused the compressor to run non stop... the ac system thought the evaporator was not cold so it continued to keep trying when infact it was well cold enough then froze up. Only way i knew was mist coming out of the vents