Aircon turning itself off intermittently

[sandman Member Find all posts View Profile Close sandman]

Hi Folks

As its getting hotter in Alice Springs, its time to track down an intermittent aircon problem. Basically the compressor is turning itself off and staying off (randomly), this I know because load on the engine changes. If I turn the dash switch off and leave for 10 seconds and turn back on it will turn on.. Sometimes it stays on without issue and sometimes it will run for a period and turn itself off again. Though today I turned it off for a while and it wouldn't turn back on however when I got home, it was on again....don't you just love it :-)

It's been to the aircon guy and he cant make it fail, he replaced the relay and pressure tested the system, all ok. I have a few questions that I hope will get answer to help me pinpoint what I need to replace.....

1) On the 120 with basic aircon, does the solenoid in the aircon clutch (driven by belt) always stay on ie: apply load to motor ? OR does the clutch turn itself on and off as needed even through 12V is applied constantly ?
2) I gather that aircon has some sort of safety system to make sure there isnt too much pressure or too little ? Where is this switch ? I've had the system pressure tested and its perfect...
3) Is there another safety system in the aircon to protect it ?

I cant see it being anything outside of the compressor assembly besides the usual wiring ie: switch, relay ?

Any experience in this area would be appreciated

Pete

[rags Advanced Member Find all posts View Profile Close rags]

I had a similar problem,replaced the relay and regassed and been good ever since. There are a couple of threads on PP relating to this issue with the 120s air. Try via google search

[SWR Banned Find all posts View Profile Close SWR]

Gday sandman

I used to do A/C instalation's and it sounds like your evapourator is freezing! Simple way to test this is to put your A/C on reserculate with a thermomentor in the centre dash vent with the fan on low speed and see if temp goes below 6 Deg Cel.

Chances are is that if the A/C temp goes to 3 Deg or lower then your Evap will freez!

Cheers

[sandman Member Find all posts View Profile Close sandman]

I had a similar problem,replaced the relay and regassed and been good ever since. There are a couple of threads on PP relating to this issue with the 120s air. Try via google search

Rags, thanks mate... Yup, done that, relay and regass.....

[sandman Member Find all posts View Profile Close sandman]

Gday sandman

I used to do A/C instalation's and it sounds like your evapourator is freezing! Simple way to test this is to put your A/C on reserculate with a thermomentor in the centre dash vent with the fan on low speed and see if temp goes below 6 Deg Cel.

Chances are is that if the A/C temp goes to 3 Deg or lower then your Evap will freez!

Cheers

Skywalkerrun

Ok, will try that....Where is the EVAP unit, is that where the air blower is ?

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

If the evap freezes it will block the airflow and you will have minimal air out the vents even if you turn the fan on flat out you will have virtually nothing coming out the vents and normally of this occurs the compressor will stay on as the thermistor isn't getting a reading low enough as the air is blocked by the evap freezing up stopping airflow over the thermistor. The compressor on the 120's is meant to cut in and out, when on you will see the clutch engage and will be spinning and when compressor off will not be spinning. You could always bypass the pressure switch just to eliminate that as been the issue. Just use a loop wire on the switch but do not run the air on all the time with this in place as the switch us there for reason which is high and low pressures to protect the system. You can do it just to see if this is the issue. I doubt it's a TX valve as this normally doesn't turn compressor off it just stops the gas getting cold so you would be getting cold and normal temp air coming through the vents. I would try the switch first. Could be faulty. There really isn't a lot involved with an aircon system in a car although they are more computer controlled then they were before. Not sure on the prados but some vehicles if the engine gets too hot the computer will automatically stop the aircon I'm sure patrols have this feature. It may be a temp sender that gives a signal to the ecu to shit air down thinking the engine is too hot, I'm only guessing on this point as I said I don't know if the Prado even has this, I'd be surprised if it didn't....... Cheers Steve

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

What's the engine temperature like?

If the engine gets to hot the air conditioning will shut down.

If there is a lack of cooling the aircon will also over pressure and shut down.

Check you viscous hub on the engine fan, very common for them to loose the
silicon oil and not engage.

If the fan doesn't roar when you first start the engine the hub is most likely
slipping. You will also notice engine over heating when working at low speeds
climbing hills etc.

Cheers
Leigh

[johna Member Find all posts View Profile Close johna]

Had exactly the same problem recently. Finally located fault to the relay being intermittent in operation. Swapped it with the fog light relay ( identical relay, and digital, big $$$ for Toyota relay),, and bought a mechanical relay for $15-00 which is doing the job so far.

[sandman Member Find all posts View Profile Close sandman]

What's the engine temperature like?

If the engine gets to hot the air conditioning will shut down.

If there is a lack of cooling the aircon will also over pressure and shut down.

Check you viscous hub on the engine fan, very common for them to loose the
silicon oil and not engage.

If the fan doesn't roar when you first start the engine the hub is most likely
slipping. You will also notice engine over heating when working at low speeds
climbing hills etc.

Cheers
Leigh

leigh, thanks.. Engine temps are absolutely fine....

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

I am starting to experience he same problem with my MY12 GLX Prado. The aircon works fine then all of a sudden it stops blowing cool air (smells stale etc.) It has happened a couple of times now so I booked it in with Toyota for an inspection yesterday but it was working fine when they looked at it (which I knew would be my luck). What ticked me off is they can't do anything about it, will not replace any parts until they actually inspect it when its not working. Anyone else had this problem and found the problem? Otherwise I have a useless vehicle for the Queensland weather.

Great to know I have a $65 000 vehicle with an aircon. that works when it feels like it, and Toyota does not want to try and fix the problem... A Great Wall probably has better aircon

[johna Member Find all posts View Profile Close johna]

Remember reading in PP long time ago re the thermistor being too close to the evap and causing the compressor to short cycle. There was instructions on how to adjust the distance from the evap coil to stop problem.

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

http://www.pradopoint.com/showthread...03-Cold-Aircon Cheers Steve

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

I had a similar issue last summer but the aircon light would flash when the compressor cut out which turned out to be a relay. Replaced and haven't had an issue since !