Previas Air Con Cools Then Stops

[stjoolzz]

I have a 1996 Previa Motiv-8. The air con works for between 45 and 90 minutes and then stops cooling. The Light on the AC button is on, the fan is on and the revs are still increased however the cooling stops. If I turn the AC button off the revs drop again.

If I leave the car and then try the next day, for example, it works again. I have had it serviced but it does the same thing.

Any suggestions?

[zaphodbb]

Not familiar with the Previa's internals, but, if it's just Air-Con then you should be able to see the compressor clutch engage when the air-con's working. If it drops out after the time you mention then either it thinks it's reached the correct temp or the temp sensor itself may be faulty (this is normaly behind the dash somewhere). Another thing to look at is it may be low on gas, there should be a sight glass down by the heat exchanger (radiator) at the front. See if there are any bubbles when it's working. bubbles=low gas

[stjoolzz]

Thanks. It has just been re-gassed and at the same time they replaced the heater control valve.. the garage that I usually take it to are stumped (although as far as they were concerned it was working after half an hour so its fine) I do not rally want to take it to the main dealer because they will charge the earth. I wil have a look at what you suggested. I have ordered a book :bookworm: which, hopefully, will give me some clues as to what I am looking at

[blobstrom]

There is a thermistor somewhere cabin side of the evaporator, my AC used to cycle on and off after being on for only a few minutes. In the ennd I fund the AC control box (drivers side attached to the heater by your feet) and soldered a 470ohm resistor where the thermistor connects, so now it will keep on running as long as it doesn't go high pressure. Obviously on moist days you have to make sure the evaporator doesn't freeze up, but I don't think thats an issue in the UK, where you would normally run it when it gets hot out, about twice a year for 5 minutes :D

[stjoolzz]

thanks - I will have a look. I do use the air con a fair amount (well I did) Use it in the winter too for demisting (excellent) however the other day I could tell that it stopped cooling because the windscreen misted up within seconds

[stjoolzz]

I noticed today that the aircon not work is not related to whether it has been on or not. Having driven around for an hour or so I turned it on and all I got was warmish air. After leaving the car for a couple of hours to cool down, it worked. This leads me to suspect that it is a temperature problem (fantastic powers of deduction there). I will look up my new book/manual and see what it says.

[blobstrom]

I doubt if you will find anything useful, thats why I went for the resistor

[stjoolzz]

<_<

Of course you were right - there is naff all in the book (these american books are so satety/litigation conscious)

I will try to have a root around this weekend and look at where I would put this resistor. The Toyota garage says it is almost certainly a leak that is causing it but it has dye in now so it should show.

I don't suppose you have any pictures of what you did??

[stjoolzz]

I have a 1996 Previa Motiv-8. The air con  works for between 45 and 90 minutes and then stops cooling. The Light on the AC button is on, the fan is on and the revs are still increased however the cooling stops. If I turn the AC button off the revs drop again.

If I leave the car and then try the next day, for example, it works again. I have had it serviced but it does the same thing.

Any suggestions?

←

Well I finally solved the problem. I posted emails in the yahoogroups toyota previa group and got all sorts of replies. Several pointed the same way (after lots of head scratching) and last month I had the Expansion valve replaced. It had worked beautifully since then.