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Discussion Starter · #1 ·
hi guys i recently changed my aircon pump/compressor as it was noisy with a 2nd hand one. I now notice my fan does not come on. blowers fine in the car as is the switch but at 16c all i get is warm air any ideas welcome please.
 

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how is your air temp sensor under the front bumper? does the dash read the correct outside temp?
 

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Discussion Starter · #3 ·
hi
thanks for the prompt reply. My mates got it out today so i dont know (sods law) would it make a difference like to the aircon fan? or are you thinking possibly the panel inside the car?
 

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Check your final stage unit, it's a small module under the dash, passenger footwell. Does it blow very gently (but cold)? The FSU controls fan speed and is a common failure.
 

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Discussion Starter · #5 ·
hi
no it blows fine(the motors blow good) the problem is that the aircon takes ages to come through cold and even then its not that cold. When i turn off the aircon and the temp gauge shows the lowest on the lcd as 16c it still comes through as warm air.the aux fan for the aircon is not coming on at all (the one in the front grille).it was working fine until i changed the compressor though
 

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hi
no it blows fine(the motors blow good) the problem is that the aircon takes ages to come through cold and even then its not that cold. When i turn off the aircon and the temp gauge shows the lowest on the lcd as 16c it still comes through as warm air.the aux fan for the aircon is not coming on at all (the one in the front grille).it was working fine until i changed the compressor though
The auxillary fan ahead of the radiator comes on only after the A/C develops a little pressure (4 bar IIRC), i.e. it is doing some cooling. It does not start simply because the A/C has been turned on.

The auxillary fan not coming on and the lack of good cooling are both consistent with a problem in the A/C. Perhaps a low refrigerant charge &/or the used compressor is a little too used.

If a shop did the work, can you not go back and insist they correct the problem?

If you replaced the compressor yourself did you change the drier (& perhaps expansion valve) plus flush the system to ensure any debris from the old compressor is out of the system? Was the charge done correctly: vacuum at ~10mm Hg absolute pressure for ~30 minutes, verify no leaks, refrigerant added by weight to spec? How confident are you that the "new" compressor is in good condition.
 

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Discussion Starter · #7 ·
tahnks for that rdl. i have my mate checking these things today (the guy who fitted the used one) i have another used one coming tomorrow or today with 90,000 miles on so may swap for that one. He said that they only filled the refrigerant coolant 3/4 as if they filled it all up with no fan working it would blow the valve on the pump? is this true?
I also had another bmw tech guy on ebay who tooh his fan off believing it was faulty, bought a new one from "the stealers" and still no fan- ended up being a faulty dash unit? he wants £70 for his original fan? all help is greatly appreciated by the way thank you
 

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Discussion Starter · #8 ·
what I dont want to do is to change fan, pump, relays etc just to find out its a blown fuse or something stupid as it was all ok before he changed the faulty compressor/pump which was making a noise but was still working
 

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The auxillary fan being inop will not cause the refrigerant to vent even with a full charge. If pressure gets too high, the compressor clutch should disengage automatically and thus limit further increase for self protection. Assuming of course that the sensors and circuits are intact. Regardless, a 3/4 charge should still provide decent cooling. BTW, reduced refrigerant charge does not significantly reduce system pressure until the refrigerant charge is very low.

However, an inop auxillary fan will result in much reduced cooling at slow road speed; both A/C in cabin and engine coolant temp. It would be best to check aux. fan function if for no other reason than to ensure adequate engine cooling in all conditions. Note that the auxillary fan control changed sometime around 1998/1999 or so. Early design used relays with 3 stages or speeds. Later design uses a PWM signal from the engine controller with 20 or so speed increments. At least for gasoline engines & I notice you have a diesel, which may be different. Testing procedures are different of course.

Here is a link to WDS (wiring diagrams) and TIS (service manual.) WDS also describes system operation to assist with diagnose.
http://spaghetticoder.org/

I wouldn't have any regrets about changing out a noisy compressor. If it was noisy, something had obviously broken and it was probably sending debris toward the condenser and drier which would eventually make repair more expensive.

Regards the auxillary fan being offered. First, is yours really defective? Second, is it the same design as yours?
 

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Discussion Starter · #10 ·
hi rdl, thanks again for that. I think the best thing is is for me to put a live to the fan to see if it works first then if no then a new fan probably,or to change the pump again to the original one and to fully charge it to see if the fan works then if not change pump again for another.
 

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hi rdl, thanks again for that. I think the best thing is is for me to put a live to the fan to see if it works first then if no then a new fan probably,or to change the pump again to the original one and to fully charge it to see if the fan works then if not change pump again for another.
If you have the new PWM controlled fan, simply applying 12V will do nothing. In fact, that fan should have 12V at all times already. A good fan runs only when it is receiving the PWM signal from the engine controller.
If you have the older style with relays and resistor block, 12V to the fan motor leads is a workable test. With this style relays and resistor blocks are also suspects too, not the fan only.

Swapping the compressor again strikes me as a very complicated and time consuming method to test. Faster & easier to dig into WDS and check the circuits and components. It would also be worthwhile to have someone with a set of A/C pressure gauges check the A/C while running. A pressure check would take no more than 10 minutes.

A good BMW compatible diagnostic system would help. It will be able to return all the sensor values as well as activate the fan, valves etc. to aid in diagnosis. Half an hour's diagnostic from an A/C expert may well save you many hours and pounds of expense.
 
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