Aircon help

[Dansrockin]

Hi all! Can anyone suggest a solution to my fan problem? My 75 cdti cooling fan goes onto high speed when the aircon is used. Without aircon, the fan is normal, but if aircon is on, it sounds like a jet engine! 😃
I've changed the resistor to a gold one from Jules as low speed wasn't working. That now comes on if I use the demist test, and also both speeds showed up as ok on a t4. No fault codes showing up at all. The aircon was regassed about a month ago, and it blows cold, although it's not as cold as my old zt used to be.
Thanks 😃

[SD1too]

My 75 cdti cooling fan goes onto high speed when the aircon is used. Without aircon, the fan is normal ...
I've changed the resistor to a gold one ... as low speed wasn't working. That now comes on if I use the demist test ...
Dan,

I have a question before attempting to diagnose the cause of your problem.

You say that the 'demist test' results in the low speed running. This test activates the air conditioning, so why do you say that the fan runs at high speed when air con. is used? :confused: :shrug:

Simon

[Dansrockin]

sorry maybe i didnt explain too well!
when pressing the demist button, i can hear the low speed fan come on if i go to the front of the car.
if i have the aircon on while driving around, i can hear the high speed fan on. also when i turn the car off, if the aircon has been on, the high speed fan continues to run for a few seconds.
it doesnt seem to go straight to high speed, if i put the aircon on when the engine is cold, then it will go to low speed, but once the engine warms up a bit, or if its particularly warm outside, then high speed kicks in.

[SD1too]

OK Dan, thanks for the further explanation. :}
... it doesnt seem to go straight to high speed, if i put the aircon on when the engine is cold, then it will go to low speed, but once the engine warms up a bit, or if its particularly warm outside, then high speed kicks in.
That sounds about right to me. The trinary switch will call for increased forced cooling of the condenser in hot conditions, or when the car is stationary with no 'ram effect'. It could also occur if your condenser has lost a lot of its fins to corrosion, so that's worth checking.

I should also make sure that you didn't regas your air conditioning using a DIY canister of refrigerant. :o If the system was recharged by machine, was the circuit opened prior to that for component renewal? If so, the drier could be saturated with moisture and the servicing agents' standard of ten minutes vacuum is, according to the theory, inadequate to remove it and that can affect cooling performance.

Simon

[Dansrockin]

i did wonder if it was due to temp recently, but none of my other 75s or zts have done this with the high speed unless the fan was faulty.
i didnt use a diy kit!!! :eek:
it was recharged about a month ago by hiq (i know, not as good as a proper aircon specialist, but they were only charging £29! :D )
ive been told its possibly a symptom of the system over pressurising, either due to condenser being blocked up, or missing lots of fins as you said, or they system being overfilled.
its going back in on monday for them to check it and empty and refill, so if it doesnt come back any better, ill have a good look at the condenser and drier.
cheers
dan

[HarryM1BYT]

sorry maybe i didnt explain too well!
when pressing the demist button, i can hear the low speed fan come on if i go to the front of the car.
if i have the aircon on while driving around, i can hear the high speed fan on. also when i turn the car off, if the aircon has been on, the high speed fan continues to run for a few seconds.
it doesnt seem to go straight to high speed, if i put the aircon on when the engine is cold, then it will go to low speed, but once the engine warms up a bit, or if its particularly warm outside, then high speed kicks in.

That sounds to be about right...

If the a/c cannot get rid of its heat fast enough on the slow speed, it will sometimes turn on the high speed. This will most often happen when you are travelling slow and / or when you come to a stop. The action concerned me enough last year, that I had my a/c given a full and proper service last year by a specialist - the verdict was that it didn't need anything done at all, it had lost no fluid and 'the radiator' at the front was in good condition.

'The radiator' at the front might be worth your checking it. The fins suffer corrosion from salt, it can become less effective and that can cause the fan to come on more than it should.

[SD1too]

... or the system being overfilled.
That shouldn't be the case with the special professional machines. I hope that the label stating 450g (± 50g) is still in place beside your bonnet catch. All the operator needs to do is to enter that figure into his machine.
..I'll have a good look at the condenser and drier.
The drier is a dessicant pack sealed into a tube which is part of the condenser. If your circuit hasn't been opened it should be OK, but if you can persuade your operator to hold a vacuum for 30 minutes (most are reluctant) that will successfully remove any stored moisture.

I'd be interested to hear what happens on Monday. :}

Simon

[HarryM1BYT]

The drier is a dessicant pack sealed into a tube which is part of the condenser. If your circuit hasn't been opened it should be OK, but if you can persuade your operator to hold a vacuum for 30 minutes (most are reluctant) that will successfully remove any stored moisture.

I'd be interested to hear what happens on Monday. :}

Simon

The guy I got, did that unasked. I did ask him though what the wait was for;)

[spider13]

Most modern ac machines will hold a vacuum automatically and also should do a leakntest

[Dansrockin]

Well I took it back in today, asked them if they could put a longer vacuum on just to make sure. 90 mins later he called to say it was all done, no issues found.
The aircon is now blowing slightly colder, he measured 5.4c, and so far fingers crossed, only the low speed fan kicks in. I stood there a good 5 mins with him while the aircon was on, before the high speed fan would come on within around 30 seconds.
Seems to be sorted!
Thanks all for the suggestions

[suzublu]

Moved to Technical help, better late than never:o:D