Air Con randomly working and not working

[climbingmike]

Hello All

I have been having issues with my AC for a while now. I have just got back form a 5 hour drive in about 35c heat. The AC will be working fine and then stop, The blower is still on just no cold air just out side air temp. After a while it will come back, then off again. It sometime takes 30 mins before it stops and sometimes within 10 mins of starting the car.

I have replaced the condenser radiator because the dealer said there was a leak and the system has been regassed but this as a few months ago and am still having the issue. I am thinking the compressor but as this is an expressive unit I want to know if it could be any thing else or if there is a way to test. I also thought that it might be the solenoid that engages and disengages the compressor pulley.

If any one has any advices it would be much appreciated. I dont want to have to go though another long drive with doggy AC

Many thanks
MIke

[ChrisF]

does the condensor fan come on ?

when the system works hard, the high pressure goes up and up, then the fan is supposed to come on. If not, there may be a safety switch cutting out the ac when the pressure gets too high ....


but it could be a number of other stuff as well.

[Mud Dog]

Most units don't have a separate condenser fan and rely on air drawn through by the radiator fan.

I also thought that it might be the solenoid that engages and disengages the compressor pulley.

This is the first place I would look for an intermittent fault as you describe - it could just be a poor connection either at the compressor itself or at the thermocouple that activates the compressor.

[climbingmike]

It turns out to be the engine temp getting to hot and cutting out the AC. I am hoping that servicing the viscous fan will solve the issue :)

[CasKru]

Mike... it could be that the system has been overfilled as well. As Chris said as the temp rises the pressure builds and builds.

I though I was clever on my wives vehicle. The AC worked fine but I though it wasn't cold enough. I then bought one of these cans one can fill the AC one self and followed the instructions religiously.

After I finished the AC was colder but would do exactly the same yours is doing. I then released some gas out of the system to try and remove the ones I added a little bit at a time to get it back to what it was before and not to release to much gas and it is now back to normal.

[climbingmike]

Thanks for the info. I will bear that in mind if the issue continues.

Many thanks
MIke

[Thunder02]

Hi Mike, I found out this past weekend, it is a safety feature built into the vehicle. If the engine starts to get too hot, it will cut off the air con until engine temperature drops down.
So no problems with your Hilux.

[ChrisF]

Hi Mike, I found out this past weekend, it is a safety feature built into the vehicle. If the engine starts to get too hot, it will cut off the air con until engine temperature drops down.
So no problems with your Hilux.

There are actually MANY items that control the clutch of the air conditioning, depending on the brand and model. These may include:

1) thermostat - if the ac thinks it is cold enough the ac will shut down. faulty thermostat could be a possibility
2) high pressure switch - there is a two stage high pressure switch, once the condensor pressure gets high enough the electric fan kicks in. If the pressure continues to go up, at a higher pressure the clutch will cut out as a safety. If the fan does not start, for any one of many reasons the pressure goes up !!
3) low pressure - there is also a low pressure switch to prevent the system running into a vacuum after a gas leak.
4) evaporator fan - the inside fan MUST run for the ac to work safely. Different vehicles have different interlinks and/or air flow switches to ensure this
5) and then with many modern vehicles the engine ECU parameters are used to shut down the AC if the vehicle runs hot, or if the EGT goes too high
6) on some small engined cars a "kick down" switch concept is used to cut out the AC if you need all the engine power.


These are but a few of the factors the modern car designers use.



in terms of solving an intermittend problem .... short of seeing error codes on the computer it becomes a nightmare for an autoelectrician to figure out which one of these many factors are at play .... though a decent air con machie will know how to test for the correct pressures and if the condensor fan comes on, etc.

[Peter Botha]

I am the proud owner of a 2005 Hilux D4D 2.5 4X4 double cab. A month ago I started to have the same problem with the aircon, and after chatting with some motor mac friends, they all told me that the pollen filter needed to be replaced. Well now, there is no pollen filter fitted to the Hilux, therefore the evaporator in the cab gets seriously blocked. I have just had the dash removed, the evaporator pressure cleaned, replaced and the aircon performs like new again!

There is a position for a pollen filter just above the blower behind the cubby hole (glove compartment), only the cover plate is not removable, but can be cut out with a sharp trimming knife, a easy modification to increase the size, purchase a Hilux pollen filter and insert it into the slot, replace the modified cover, and your evaporator is protected!

[Peter Botha]

Further to the evaporator cleaned and refitted, the aircon working again, can anybody please inform me as to why Toyota does not fit pollen filters to some of their Hilux vehicles? Should anybody like to have a copy of the dash removed and a copy of the blocked evaporator, supply me with your what's app or email add and I will gladly supply the pics.

[Mars]

The earlier models did not have a pollen filter.

[Ronwob]

It is possible that the unit freezes up. After switching it off and giving it time to defrost, the unit will work again. This happened to me.

[Mars]

It can definitely freeze up if the evaporator/heat exchanger is blocked.

I had a VW Fox many years back with an aftermarket aircon. The installers blanked off half of the evaporator for some reason known only to them. The aircon was very inefficient and I eventually came to the conclusion that it must be freezing up. When I started stripping I found the plate over half the evaporator. I removed it and the aircon started working really well after that.