A/C Thermo Fan Problems

[XHPBT1]

Hi All,

I have recently noticed that my A/C isnt working like it should, It turns on then off after a little bit of time and then about 10mins later it turns on again (as in starts cooling)

the Thermo Fan for the A/C seems not to be working at all,

Had it looked by a A/C Mechanic and he said gases are all good, but its most likely the thermo fan.

Has anyone else had something like this?

cheers
DJ

[wopac5]

Haven't, yet, had the issue, but check for power to the fan, use a multi-meter to check for power, or a test light,...this will check the fuse, and the fan motor depending on what you find.
However, once at speed with natural air flow, I would expect the air con to work as normal regardless of the electric fan on or not.
If it's not working at speed, I suspect it may be more than the fan?

[Jason789]

Hello XHPBT1,

Check that your condensor for the A/C isn't blocked with crud. When I changed my radiator, I was amazed at the amount of dirt and bugs that were blocking it. a Karcher with the flat spray pattern will do a good job for this(don't use the spinning head attachment, it will damage the fins).
Compressed air would probably be easier with out having to pull everything apart.
A/C with high head pressures and temps lose efficiency to cool.
Try the blast out of dirt and bugs, then re assess.

Cheers,

Jason

[Urban Panzer]

Hi All,

I have recently noticed that my A/C isnt working like it should, It turns on then off after a little bit of time and then about 10mins later it turns on again (as in starts cooling)

the Thermo Fan for the A/C seems not to be working at all,

Had it looked by a A/C Mechanic and he said gases are all good, but its most likely the thermo fan.

Has anyone else had something like this?

cheers
DJ

The compressor does not run all the time, "coming in and out" as you describe is normal.

also because the engine has the large viscous fan, the Aircon fan does NOT operate automatically when the aircon is on, it only comes on when the temp is +28°C AND the vehicle speed is less than 80 KM/h

It's not uncommon for the Aircon fans to sieze up because of the lack of use on the Diesel engined cars. Dunking it in water and mud dont help either :angel:

If you have access to diagnostics, there is an option to run the aircon fan to test it, failing that use 2 female spade connectors, a length of wire and test it at the plug of a portable jump pack or battery, if it runs, then there is no problem.

If you suspect it is seized, and you have a factory bumper / front end, simply put a long stick or similar through the grille and see if you can spin it, it should turn VERY easily. If you have a bull bar like ARB etc, you can simply lay underneath and spin it with your fingers to see if its free or not.

For a point of interest, the engine ECU can also request the aircon fan for additonal cooling in an overheat situation as well.

[XHPBT1]

Thanks guys for your wisdom, will do a few things suggested on the weekend,

just wondering how to know when the a\c compressor is shagged? Also if the a/c compressor is still cycling is there anything else stopping it cool apart from tr condenser being to hot?

[Jason789]

Hello XHPBT1,

Its hard to do a compressor efficiency test on a car A/C. The suction and discharge ports don't have the appropriate access valves. The only way is to bench test, although this is most likely to be un-necesary. Generally a stuffed compressor will sound like a cold diesel motor on start up.

General faults on a refrigeration system are(in no order of importance)
1) Compressor
2) T/Stat
3) Evaporator
4) Condensor
5) Gas charge

These all have subsidiary problems of their own.

Sometimes it's just a matter of having to pay a professional to fix the problem. It's not because an 'average joe' couldn't fix the problem. It's because of the cost of tools to be able to do the job properly.
Fixing a fridge is easy, I know, I'm qualified and I'm not a brain surgeon.
It's just the price of the specialized tools to fix the problem that make it cheaper to pay a proffesional to do the job.

Cheers,

Jason

[LR2Luver]

Hello XHPBT1,

Check that your condensor for the A/C isn't blocked with crud. When I changed my radiator, I was amazed at the amount of dirt and bugs that were blocking it. a Karcher with the flat spray pattern will do a good job for this(don't use the spinning head attachment, it will damage the fins).
Compressed air would probably be easier with out having to pull everything apart.
A/C with high head pressures and temps lose efficiency to cool.
Try the blast out of dirt and bugs, then re assess.

Cheers,

Jason

Just a word of caution on using a water blaster - if you have grass seeds in your fins they will expand with the moisture (if they haven't already) and be impossible to remove. Compressed air would be a far better way to clean the fins.

[northiam]

Generally just touching or measuring the temperature of the refrigerant pipes can tell you a lot!
With the compressor running (the centre of the comp pulley rotating)


The pipe from the comp to the condenser (in front of the radiator) should be hotter than you can hold on to... 100deg c or so...

The 10mm pipe (liquid line) than connects the condenser to the firewall should be warm to touch up to 20degc above surrounding ambient temp...
If this line gets to hot +60degc indicates lack of airflow through condenser to cool the gases i.e.: dirty condenser or radiator, faulty fans etc....

The larger pipe than exits the firewall back to the compressor would be cold and sometimes icing


The above assumes the compressor can run for a minute or two. The ambient is above 22degc


The compressor can cycle on and off normally thermostatically sensing the cooler temperature.
The comp may cycle off prematurely on the high pressure switch to protect components from over pressure. :)
A really rough guide

[XHPBT1]

Thanks for all the knowledge, today I had a look at it, tested the thermo fan and that's working, installed a monitoring light of the a/c comp. What I noticed is that the comp cuts in and out constantly, like every minute it would cycle then switch off. So me this seems too quick as I had the front air con and rear on fastest fan

Does anyone know where the sensor is for controlling the cycle of the a/c comp?

[XHPBT1]

Replaced the a/c relay and now it seems to be working perfectly