Fan issues . conditional overheating .
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1st Gear
Joined: Aug 2012
Posts: 7
From: Riverside , CA
Fan issues . conditional overheating .
2004.5 A4 AVANT 1.8/M6 . Recently i have been experiencing A/C cooling issues . My ambient temp gauge on the dash started reading -40* when the exterior temp. was 105* and my A/C would blow cold at highway speeds but would blow warm in stop and go traffic and would also cause my coolant temp to rise . i have since identified the issue ( faulty G89 sensor ) . The engine wont over heat IF
A. A/C is of during city driving
B. ambient temp is 80* with A/C at idle ( it wont over heat no matter how long i leave it sitting at idle with the A/C on or off ) .
What i did notice is that the passengers side fan does come on when i turn on the A/C but no matter how long i drive the car or how long it sits at idle the drivers side fan wont come on . I have read this can be caused by
A. bad fan motor
B. bad fan control module
C. bad fan relay
D. bad fan circuit fuse
E. Bad fan switch
F. bad coolant temp sensor ( wrong coolant temp readings not allowing fan to turn on at correct temp. ) .
the odometer is read 111,000 , i did the ECS tuning timing belt kit @ 103,356
along with cam chain tensioner , coolant flange and valve cover gaskets .
correct me if i'm wrong but I think the fan control module can be ruled out since the passengers side fan does come on . i would like to check for the fuse but don't know where it is located . i have read that the relay is under the ECM , but don't know witch number it is . and as for the fan motor , well , i will leave that for last as long as fuse and relay check out ok . Can a bad G89 sensor affect fan operation ? i think the only thing keeping the engine from over heating right now is constant air flow or the passengers side fan . any advice that brings me closer to solving this issue would be greatly appreciated .
A. A/C is of during city driving
B. ambient temp is 80* with A/C at idle ( it wont over heat no matter how long i leave it sitting at idle with the A/C on or off ) .
What i did notice is that the passengers side fan does come on when i turn on the A/C but no matter how long i drive the car or how long it sits at idle the drivers side fan wont come on . I have read this can be caused by
A. bad fan motor
B. bad fan control module
C. bad fan relay
D. bad fan circuit fuse
E. Bad fan switch
F. bad coolant temp sensor ( wrong coolant temp readings not allowing fan to turn on at correct temp. ) .
the odometer is read 111,000 , i did the ECS tuning timing belt kit @ 103,356
along with cam chain tensioner , coolant flange and valve cover gaskets .
correct me if i'm wrong but I think the fan control module can be ruled out since the passengers side fan does come on . i would like to check for the fuse but don't know where it is located . i have read that the relay is under the ECM , but don't know witch number it is . and as for the fan motor , well , i will leave that for last as long as fuse and relay check out ok . Can a bad G89 sensor affect fan operation ? i think the only thing keeping the engine from over heating right now is constant air flow or the passengers side fan . any advice that brings me closer to solving this issue would be greatly appreciated .
1st Gear
Joined: Aug 2012
Posts: 8
Not sure if your model fan relays are in the same position as mine, But I checked mine today. There are two relays under the ECU and two fuses in the same box. I also am not sure which is for fan, but all checked out ok. The relays closed ok and the fuses were'nt burned out. You need to take off the windscreen wiper to access the back screw on the box cover. Good luck if the wiper is stuck like mine.
Tech Certified
Joined: Jul 2009
Posts: 779
From: Connecticut
The passenger side fan is your condensor fan, it will operate when the a/c is on.
The driver side fan.
I would made sure its plugged in. When aftermarket shops or owners perform timing belt replacements they always tend to remove the entire radiator support from the car, which isn't needed.... but they do it for lack of knowledge. It is possible they unplugged it during this process.
From there i'd start with the fan relay, you need to be able to jump the fan to make sure it spins, then you need to be able to check for power at the relay. If the fan spins and the relay checks out you most likey need a fan module
The driver side fan.
I would made sure its plugged in. When aftermarket shops or owners perform timing belt replacements they always tend to remove the entire radiator support from the car, which isn't needed.... but they do it for lack of knowledge. It is possible they unplugged it during this process.
From there i'd start with the fan relay, you need to be able to jump the fan to make sure it spins, then you need to be able to check for power at the relay. If the fan spins and the relay checks out you most likey need a fan module
Thread Starter
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1st Gear
Joined: Aug 2012
Posts: 7
From: Riverside , CA
The passenger side fan is your condensor fan, it will operate when the a/c is on.
The driver side fan.
I would made sure its plugged in. When aftermarket shops or owners perform timing belt replacements they always tend to remove the entire radiator support from the car, which isn't needed.... but they do it for lack of knowledge. It is possible they unplugged it during this process.
From there i'd start with the fan relay, you need to be able to jump the fan to make sure it spins, then you need to be able to check for power at the relay. If the fan spins and the relay checks out you most likey need a fan module
The driver side fan.
I would made sure its plugged in. When aftermarket shops or owners perform timing belt replacements they always tend to remove the entire radiator support from the car, which isn't needed.... but they do it for lack of knowledge. It is possible they unplugged it during this process.
From there i'd start with the fan relay, you need to be able to jump the fan to make sure it spins, then you need to be able to check for power at the relay. If the fan spins and the relay checks out you most likey need a fan module
well , i found the fuse for the fan , it was located in the fuse panel on the side of the dashboard on the drivers side . The fuse is ok , i also found the relays (3 to be exact ) under the ECM . relay #219 controld the fans and a couple of other things . i also checked the fan control module and all the wires look fine . Fan switch is plugged in also . if the fan module was bad , would the aux. fan not work ? thats the only fan keeping my engine from over heating even with the A/C off . Oh BTW i replaced the G89 senosr but that only fixed my A/C cooling issue and nothing more .
Thread Starter
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1st Gear
Joined: Aug 2012
Posts: 7
From: Riverside , CA
Ever since I replaced the G89 switch my AC blows ice cold and my car doesn't over heat
I think that my auxiliary fan is what's keeping my engine from overheating. I still haven't seen my main fan kick on, I'm thinking of replacing the 219 relay under the ecm ( $31 from VW dealer ) . I also notice my coolant temperature Gage goes down to the second notch when going down big hills with a long slope on the highway.
I think that my auxiliary fan is what's keeping my engine from overheating. I still haven't seen my main fan kick on, I'm thinking of replacing the 219 relay under the ecm ( $31 from VW dealer ) . I also notice my coolant temperature Gage goes down to the second notch when going down big hills with a long slope on the highway.
1st Gear
Joined: Aug 2012
Posts: 8
As Audi Tek says, check the relay before you buy a new one. I'm no expert, so I try to be methodical. My relay and the fan work ok when tested independantly. The fan control module I'm told is not testable. Other people have replaced it to find that the problem was still there. It has permanent current to it (low and high amperage). I suspect it works like an up market relay and varies the current to the fan. It is an expensive part, so I figured an old 40 amp relay with an independant low amp switch would do the same. It isn't a perfect solution, (the fan will only run on high) but it has solved my overheat problem. Just flick the switch to run the fan in high mode when needed or stuck in traffic. 
Thread Starter
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1st Gear
Joined: Aug 2012
Posts: 7
From: Riverside , CA
As Audi Tek says, check the relay before you buy a new one. I'm no expert, so I try to be methodical. My relay and the fan work ok when tested independantly. The fan control module I'm told is not testable. Other people have replaced it to find that the problem was still there. It has permanent current to it (low and high amperage). I suspect it works like an up market relay and varies the current to the fan. It is an expensive part, so I figured an old 40 amp relay with an independant low amp switch would do the same. It isn't a perfect solution, (the fan will only run on high) but it has solved my overheat problem. Just flick the switch to run the fan in high mode when needed or stuck in traffic.
also found these two links . one on how to test the fan system and the other shows the internals of relay 219
http://forums.vwvortex.com/showthrea...ns-run-on-high
http://forums.tdiclub.com/showthread.php?t=266230
and a thank you to the people who made it possible to share this knowledge .
Last edited by catburner909; Aug 19, 2012 at 05:37 PM.
Thread Starter
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1st Gear
Joined: Aug 2012
Posts: 7
From: Riverside , CA
tested
going into the main fan motor but only the small auxiliary fan turned on and the main fand did nothing . Are both fans supposed to turn on ? . The auxiliary fan is on all the time and that is what's keeping from overheating unless i have the AC on in stop and go traffic . relay and fuse check out fine . also , is there supposed to be a crimp from factory connecting the fan control module and the main fan ?