Alan536123 Posted June 19, 2007 Report Share Posted June 19, 2007 Hi, A couple of days ago I bought an A4 Quattro from the auctions. On the way home I got bogged down in traffic and I noticed that the temp gauge started to creep up from the middle towards 3/4. At around 3/4 and just before the red portion the alarm came up to say that I had a coolant temperature fault. As soon as the traffic cleared the temp returned to normal. When I arrived home I allowed the car to run for a while with the bonnet up and the temperature started to rise again. At 3/4's on the temp gauge I turned the car off. At no time did either of the electric fans cut in so I think the fault lies in this area. I checked the fuse and it was OK. This car is a 3 Litre Quattro Auto, it's four years old and it has only done a Warranted 29,000 miles with one owner. I am an electrician but unfortunately the Haynes manual for this model does not come out until next month so I can't get the electrical drawing so I can trace where the fault is. Anyone out in A4 world could email set of electrical drawing ([email protected])? Anyone give me advice on what the issue is, it could be a common fault? By the way, the car uses no cooling water, the oil looks OK and it has no leaks. Alan. Link to comment Share on other sites More sharing options...
paul_tdi Posted June 20, 2007 Report Share Posted June 20, 2007 HI Alan, Welcome to TSN! Cant help at the moment with the diagram but it may be the water pump that has gone. They seem to be a week spot. Best of luck getting it sorted! Paul Link to comment Share on other sites More sharing options...
Alan536123 Posted June 20, 2007 Author Report Share Posted June 20, 2007 Thanks Paul. I have noticed threads about the water pump problem but this always seems to be on the smaller engines? Could someone confirm that the 3.0 Litre uses the same type of water pump as the smaller engines within the range. Talk on this forum suggests that the design has been changed for a pump using a metal impeller but what year was this fitted as standard (if it was). Just been for a run today and the only time the temperature started to creep up above 90 Degrees Centigrade was when I ended up stuck in traffic for around 10 minutes (went up to around 120), the fans did not come on again! Got round this by turning up the heating to full with the fan on full and this brought the temp back down while roasting me when the outside temperature was 24.5 Degrees Centigrade. PS, Just noticed that you are based in Blandford, I had my wife's Mini Cooper S Convertible uprated from 170 BHP to 230 BHP by GT Tuning, long way to Blanford from West Yorkshire. Regards, Alan. Link to comment Share on other sites More sharing options...
paul_tdi Posted June 20, 2007 Report Share Posted June 20, 2007 NO Kidding Alan, I am originally from North Yorkshire and have family in west yorks so know the drive all too well! Your best bet would be to try and get in touch with someone that has vagcom to try scanning for fault codes to assist. As it only happens in stationary traffic hopefully not the pump! Link to comment Share on other sites More sharing options...
Alan536123 Posted June 20, 2007 Author Report Share Posted June 20, 2007 Bit of an update on this issue. I have traced both fan cables back to an Aluminium finned unit that sits just behind the top of the radiator, this appears to be either a pair of solid state relays or it could something a little more sophisticated like a variable fan speed controller. It has the following connections: Orange - Fan 1 + Yellow - Fan 2 + Purple - Fan 1 – Red - 12 VDC supply Brown? - 0 VDC supply Blue - Could be a 12 VDC fan run signal or a variable signal Green - Fan 2 – Black? - Could be a 12 VDC fan run signal or a variable signal Both fans actually work if you put 12 VDC onto the Fan + side. Unit details: Valeo MH 1052 8734 79G A Beuffer 01-333-F 00107998 System HKR STG 600W BEO 959 501D Any ideas on how to test this unit? I don’t have the B***S to put a 12 VDC signal onto the signal connectors in case this comes directly from the ECU. Regards, Alan. Link to comment Share on other sites More sharing options...
Alan536123 Posted June 22, 2007 Author Report Share Posted June 22, 2007 Hi all, here is an update. This problem is now sorted, I spoke off the record to an Audi electrician and he agreed that the tests carried out pointed to the fan speed controller being at fault. Quick trip to Bolton Audi to pick one up (only one in the country), 30 Minutes to fit and both fans burst into life. Speed of the fans now adjust with coolant temperature. Thanks for your comments and I hope this info helps other owners. Ps, the cars fantastic! Alan. Link to comment Share on other sites More sharing options...
chrisan Posted June 22, 2007 Report Share Posted June 22, 2007 Nice work Alan - well done for diagnosing the fault. Link to comment Share on other sites More sharing options...
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