audi radiator fan question

Krank · Post by **Krank** » Wed Jul 09, 2008 10:02 am

I know, I know. This is a VW forum. Perhaps you can take a few minutes to help me out with this new audi I just picked up.
I just got an '82 Audi 4000 diesel. Since Audi's the red headed step child for VW, almost everything involved in the car is actually VW. The engine is a 1.6 NA that's mounted front / back instead of transverse. It has a 5 speed. It's kissin' cousins to a Quantum.
Yesterday I noticed the radiator fans (it has two of them) didn't seem to be coming on. It was 92 degrees out, and the car doesn't have A/C. Since the car was new to me, I was paying close attention to see how it handled the heat. That was when I noticed that neither fan seemed to cycle, and that the temperature seemed to climb much higher than I was comfortable with.
There doesn't seem to be any documentation on this vehicle... anywhere.
I haven't dealt with a two fan radiator setup before, so I thought I'd toss it out there. Here's what I see.
There's two different kinds of fans on the shroud. The one on the passenger side seems to be hardwired in (from the factory... it's obviously not some sort of hack job). The other fan motor seems to be identical to the fan motor in my '81 rabbit.
The passenger side of the radiator has (what looks like) a thermal switch down towards the bottom. It's in the completely opposite from my rabbit's thermal switch. I jumpered it, and the passenger side fan kicked in. Note that the drivers side fan did not.
I found another thermal switch looking thing down towards the bottom on the driver's side of the radiator, and jumpered the wires for this one. The drivers side radiator fan did NOT kick in. I checked for voltage, and there didn't seem to be any on either lead that came off this switch looking device.
Since there's no documentation and I don't know anyone with any experience in two fan systems, I thought I'd toss it out there and ask if someone else had ever dealt with one of these, or had something usefull to contribute.
Help?

82vdub · Post by **82vdub** » Wed Jul 09, 2008 10:35 am

I don't know this for a fact, but I believe the two fans operated separately off two temp switches, which you've apparently found. If one can't cool it enough, the second fan comes on. That's what I believe, but have zero experience with an Audi or dual fan setup.

Quantum-man · Post by **Quantum-man** » Wed Jul 09, 2008 2:56 pm

In the Haynes manual for the Quantum, there was an option for a 2 fan system. They were fused separately but the first stage had to be running to set off a relay that then allowed the 2nd fan to come in when the higher temp switch was also triggered. Audi may be similar...ish

So you may have a combination of a fuse out, or the temp sensor out or the relay out or ,.... you haven't reached critical temp?

tylernt · Post by **tylernt** » Wed Jul 09, 2008 8:48 pm

Quantum-man wrote:So you may have a combination of a fuse out, or the temp sensor out or the relay out or ,.... you haven't reached critical temp?

Yeah, I wouldn't trust the gauge. Stick a meat or candy thermometer into the coolant somehow (hopefully it has an overflow tank with a steady stream of coolant coming into it, like a VW) and measure directly. Fans should come on somewhere north of 212Â°F I would guess.

Krank · Post by **Krank** » Thu Jul 10, 2008 9:20 am

You guys are great! Thanks.
(competitor's name removed by moderator) lists a radiator fan relay for this car, NAPA showed two seperate thermal switches (one that went closed at around 190 and opened at 180, the other cycled both on and off at just over 200), and my fuse panel cover does seem to show two fuses. I think you've described what's in this car, so now I'm just going to shotgun all the parts and see what starts working!
Thanks again!

vstech · Post by **vstech** » Thu Jul 10, 2008 12:07 pm

any chance a bently or haynes manual would show the wiring and fuse layout on this setup?
I would test before replacing parts. could just be a fuse, and a thermostat issue.
post some pics of this car!

Quantum-man · Post by **Quantum-man** » Thu Jul 10, 2008 1:28 pm

vstech wrote:any chance a bently or haynes manual would show the wiring and fuse layout on this setup?
I would test before replacing parts. could just be a fuse, and a thermostat issue.
post some pics of this car!

I'd hotwire the secondary fan direct from the battery to see that it worked and then check the rad switch by removing and playing a flame on it gently whilst checking it's resistance. Hot water or steam from a kettle may not do it

If you can find the relay then some have their circuit printed on it but it may just be a simple 4 terminal job that is easy t otickle into life! Fuses should be easy

Krank · Post by **Krank** » Thu Jul 10, 2008 1:32 pm

I suppose if you could find a Bently or a Haynes for a diesel of this model, then yes. Thus far the only thing I've been able to get is a Haynes manual for a gas version (schematics don't seem to compare well) and a factory manual (800 pages) that I've ordered from Amazon but haven't recieved yet.
I've got a freind with an A2 Jetta that has the same exact setup, so I think it's a fairly universal design. I just went down and bought a sensor and a relay for a whopping $25. If it doesn't cure it, then I can be assured it probably was due for renewel anyways.
I'll pop in some pictures when I get home. It's a really amazing car. The engine leaks oil (surprise surprise), but the body is almost show room clean! I just had a stereo installed this morning, and the installer had to take time out to tell me how amazed he was at the quality of the car... how it was in almost mint condition after 26 years. He'd never seen a car in such condition for it's age. He just about dropped a brick when I told him I got it for a mere $200! The PO really didn't know what she had.

tylernt · Post by **tylernt** » Thu Jul 10, 2008 2:31 pm

Krank wrote:I've got a freind with an A2 Jetta that has the same exact setup, so I think it's a fairly universal design.

Interesting, I've never seen an Mk2 Jetta with two fans. The 16v Passat got dual fans (unsure if that's Mk2 or Mk3), but there is only 1 fan motor and the fans are connected to each other with a belt. Some Mk3 cars got dual fans with dual motors, but I've never seen them on a Mk2.

82vdub · Post by **82vdub** » Thu Jul 10, 2008 2:44 pm

And I will add that the single fan on my 82 Rabbit sure moves a hell of a lot of air when it runs. More than I would have ventured to guess by it's size.

Krank · Post by **Krank** » Fri Jul 11, 2008 8:06 am

The 16v Passat got dual fans (unsure if that's Mk2 or Mk3), but there is only 1 fan motor and the fans are connected to each other with a belt.

You are so right, and I was so mistaken.
I went to my freind to ask him about how his two fan system operates, only to discover he only had one motor with a belt that connected both fans.

I replaced one temperature switch so far. I bought a relay as well, but there appears to be more than one relay of that size / shape on the panel. Without some sort of clue as to which is the one I want to replace, I'm stalled until that 800 page manual shows up. Hope the guy delivering it has health insurance. That's one BIG book!

Back on topic, though. The new sensor allowed the passenger side fan to cycle properly. It came in 3 temperature ranges, so I chose the middle one. I'm already regretting it. It would seem I wanted the highest temperature one. The difference is only about 7 or 9 degrees, but on the gage it's the difference between barely over cold and reading mid range (a more efficient operating temperature anyway). It's so simple to change the sensor, that I'm likely to swap it out with the higher temperature version in the near future.

Thanks to all those that helped. I'm not worried at all now that I have at least one fan cycling. I know from my 81 bunny that one fan's all that's needed... the other is just gravy for when I find myself stuck in traffic, idling my way across Death Valley. Since I don't even live in that state, it's not likely to be an issue!

82vdub · Post by **82vdub** » Fri Jul 11, 2008 8:51 am

If it were me, I probably wouldn't worry about the temp setting of the switch you got. If the cooling system is working properly, the fans will never run while running down the road (of course without the AC on) and will only run when you slow down, are stopped, or in stop/go traffic etc. Then the fans will cycle on and off. So, the switch will do it's job when it's needed to work. In addition, if the second fan/switch combo is in fact a secondary fan as I think it is, it's only going to work when the other fan can't cool the coolant enough to keep the second fan from running.