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  #41  
Old 10-06-2021, 02:40 PM
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Quote:
Originally Posted by daki50 View Post
The clutch catches when I turn on the snowflake
Aux fan not work
https://youtube.com/shorts/kVLFzk-FyRk?feature=share


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Aux fan doesn't always run from AC on. Temp dependent.

Disconnecting the freon pressure sensor should spin the aux fan.

When my AC wouldn't work I had to replace my aux fan. I was able to get AC to work by manually engaging the compressor with my foxwell.

Can you see the inner part of compressor clutch turning? The two main possibilities are:

➀ clutch air gap too much and not engaging. (Click yes, spin no)

➁ variable displacement compressor stuck at zero.

Since revving makes a difference, I think it's 2. You get higher pressure than me once it kicks on.
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  #42  
Old 10-06-2021, 02:42 PM
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Given that you have to do all the exact same work to replace the valve, why not just put a brand new compressor in there? It seems like a penny wise / pound foolish decision.

You have to evacuate the system, remove the compressor, clear the lines, clean, etc. It would take more time than just putting a new compressor back in, which at the age/mileage of our cars they probably are due anyway.

But totally your call. Regardless, this is the problem AFAIK.

BTW this is not just me speculating. I had a very similar problem, when through the diagnosis, found that thread and replaced the compressor and everything worked again.
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  #43  
Old 10-06-2021, 02:43 PM
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Quote:
Originally Posted by andrewwynn View Post
Aux fan doesn't always run from AC on. Temp dependent.

Disconnecting the freon pressure sensor should spin the aux fan.

When my AC wouldn't work I had to replace my aux fan. I was able to get AC to work by manually engaging the compressor with my foxwell.

Can you see the inner part of compressor clutch turning? The two main possibilities are:

➀ clutch air gap too much and not engaging. (Click yes, spin no)

➁ variable displacement compressor stuck at zero.

Since revving makes a difference, I think it's 2. You get higher pressure than me once it kicks on.

To rotate the inner part, I will have to change the valve of the variable compressor or I will take a new compressor


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  #44  
Old 10-06-2021, 02:46 PM
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Originally Posted by Corellian Corvette View Post
Given that you have to do all the exact same work to replace the valve, why not just put a brand new compressor in there? It seems like a penny wise / pound foolish decision.

You have to evacuate the system, remove the compressor, clear the lines, clean, etc. It would take more time than just putting a new compressor back in, which at the age/mileage of our cars they probably are due anyway.

But totally your call. Regardless, this is the problem AFAIK.

BTW this is not just me speculating. I had a very similar problem, when through the diagnosis, found that thread and replaced the compressor and everything worked again.

Because the price of a compressor is much higher than the price of a valve (a compressor would say itís good because it cools like crazy). But it is possible that I will buy everything together. Thanks a lot.


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  #45  
Old 10-06-2021, 04:20 PM
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Quote:
Originally Posted by X5chemist View Post
The fan does not start up when I pull the sensor off the coolant line. So I guess my sensor is toast. Time to drain the coolant and replace it.
Just trying to add some accuracy here, copying from my notes back when debugging my failed aux fan on my 2001 3.0i (same fan on all gas-engined E53s) ...

====
Pulling the connector off the coolant temp sensor on the lower radiator hose will not turn the fan on. As detailed below, the ECU considers that to be a temp of -54*F, so not hot at all, so no need for the fan.

This has nothing to do with the temp gauge in the instrument panel. No warnings result when the temp varies to extremes.

Tests done with ignition ON, engine not running, battery charger maintaining voltage.

I used the foxwell to monitor live data on that temperature. Measured about 71F (ambient temp) when starting.

Disconnected the connector, simulating infinite resistance ==> -54*F

Measured resistance of the sender = 2.8 kOhms

Put the following resistors across the connector to simulate different temperatures:
temp [F] resistance [kOhms]
-54 infinity (unplugged)
71 2.8 (actual sensor)
94 1.48
122 0.80
159 0.40
213 0.151
241 0.100

These were done to confirm how I could simulate an overheated radiator hose, to hopefully trigger the fan to turn. Interweb lore says that you can just unplug the sensor, but that does not seem to work, which makes sense.

The 100 Ohm resistor simulates 241F, and successfully triggers the fan to come on (the command comes [command voltage signal drops], even though the fan did not spin while I was doing these tests - because my fan was broken).

====
Pulling the connector off the AC pressure sensor, nearby, while the AC is turned on and the engine running, the aux fan should spin. More specifically as I tested it on my car:

(AC pressure sensor voltages given in an earlier post in this thread)

When the AC was turned on, the fan control signal dropped from its normal (fan off) state of 14V to 12 .. 11V, as before.

When the AC pressure sensor connector was removed, it very quickly ramped down, at about one Volt per second, ending at about 2.0V, which should be almost top speed for the fan.
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  #46  
Old 10-12-2021, 05:03 AM
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Originally Posted by daki50 View Post
Because the price of a compressor is much higher than the price of a valve (a compressor would say itís good because it cools like crazy). But it is possible that I will buy everything together. Thanks a lot.


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Corvette is right.
Even though the valve is the problem; itís more than that -
Itís the design of the variable displacement compressor that leads to this issue, that pressure must increase ( by you increasing rpmís to 3000) ; that even if you replace the valve with a brand new one , the issue may still be there - due to wear surrounding the valve or other unknown issues ;

Thatís why itíd make sense to replace compressor with a conventional type , rather than another variable displacement, because even a brand new one problem may still be there , or return after a relatively short time as tolerances possibly grow requiring your 3000 rpm fix to get the compressor to actually kick in - once itís working- itíll stay working-
until the next day when itís cooled down, and retracts and youíve gotta go through it all againÖ-
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  #47  
Old 10-12-2021, 05:33 AM
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Originally Posted by deepblonde View Post
Corvette is right.
Even though the valve is the problem; itís more than that -
Itís the design of the variable displacement compressor that leads to this issue, that pressure must increase ( by you increasing rpmís to 3000) ; that even if you replace the valve with a brand new one , the issue may still be there - due to wear surrounding the valve or other unknown issues ;

Thatís why itíd make sense to replace compressor with a conventional type , rather than another variable displacement, because even a brand new one problem may still be there , or return after a relatively short time as tolerances possibly grow requiring your 3000 rpm fix to get the compressor to actually kick in - once itís working- itíll stay working-
until the next day when itís cooled down, and retracts and youíve gotta go through it all againÖ-

Are you sure about what you're saying? Do you think that the problem could continue after the valve is replaced?


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  #48  
Old 10-12-2021, 05:03 PM
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Originally Posted by daki50 View Post
Are you sure about what you're saying? Do you think that the problem could continue after the valve is replaced?


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Am I certain?

Nope I could be wrong.

You may be lucky and replacing just valve fixes everything;
or maybe you only need to rev to 2000rpms , or your 15 year old compressor lasts another year or two with the fix Ö

The more expensive V8 models just use a conventional compressorÖ

Wouldnít it be nice to just turn the key and get ice cold air almost immediately while itís idling at only 600rpm?

Iím merely giving you a heads up Ö
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  #49  
Old 10-12-2021, 05:07 PM
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Are you really willing to bet all that time to try and change a valve in a 15 year old compressor vs. putting in a brand new one that will likely outlast the car and work perfectly?

I understand there are cost considerations but I can't see any benefit to even trying this.

Regarding converting to a conventional compressor - my understanding is that making that change requires other changes to the system (I can't seem to recall which ones) but it wasn't as straightforward as just changing it out like-for-like.

I just kept it simple - my original compressor went 16 years and 160K miles before it started acting up. It was no more $$ to put the variable rate one back in, and it will likely never need to be changed again and it worked great for a long time, so the effort to swap didn't really seem to be worth it.
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  #50  
Old 10-12-2021, 05:26 PM
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Nothing, it is best to replace it with a new one and then I am sure it will work properly. Thank you for the tips a lot


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