downbytheriver

Thanks in advance for checking out my thread - any advice is greatly appreciated!

I've a '97 A6 with the 2.8 that runs great, burns no oil and which has been really great to me over the years. We've been up Pikes Peak twice together and everywhere in between the Northwest Territories and Miami Florida.

I've performed a couple belt changes & water pumps (at the same time), an alternator, an ignition switch and a couple transmission fluid/filter changes...a few other periodic maintainance type things over the years but nothing too awfully labor intensive and time consuming.

Anyway, I recently noticed that neither coolant fans were operating.

I've checked every fuse in the box beside the driver's side door, between it and the dash. I've checked the large fuses in the floorboard drivers side next to left footwell, under the bonnet/hood release lever. I've checked all the fuses in the box under the hood driver's side.

I found no blown fuses.

I replaced the 2 speed switch in the bottom driver's side of the radiator.

I then replaced the relay switch in the #3 position in the box under the hood drivers side there by the firewall.

Still, after all this - When I run the airconditioning it blows cold and yet when I get out and check under the hood neither fan operates.

So, I pulled the fans and connected them to battery and they both spin fast and furiously, extremely quietly even!

Well, knowing they moth work, I splice the wires, put them back in.

Then, I learn theres another relay in the #2 position that may b e the problem, so I pull it, test it with resistance meter and jumper and low-and-behold it makes no "click" so I run to parts shop and replace it.

NOW, when I crank her up and turn the airconditioning on , BOTH fans spin. And when I turn A/C off, they both stop. I let it idle to warm up and eventually the coolant starts to bubble out fill tank and I shut her down.

Well, thinking I was closer to having the problem solved, I cut the fans again and switched the wires in case I'd spliced them back together incorrectly the first time.

well, I let her warm up again and again neither fans comes on (unless I turn on A/C in which case they both run wonderfully).

I don't know where to turn at this point? I'm guessing maybe the coolant isn't flowing past my new switch in radiator? I just replaced the thermostat a few months back when I did a timing belt and waterpump...is it possible I guess that the thermostat is bad? Would it be stuck closed I guess?

Is there a vapor lock or air in the lines since I had to drain the coolant to replace the switch in the bottom of the radiator? If so, does one remove the excess air with the flat-head screw bleeder valve located up almost under the windshield? Does the coolant need to be warm when the bleeder valve is loosened?

Are there other issues I should explore??

Thanks again for taking the time to read my tread - I greatly appreciate any feedback and consideration!

Best,

downbytheriver in NC

downbytheriver

So, I tried bleeding any the air from the system but I'm not convinced I'm getting the proper coolant flow.

I turned the heat on and the heater fan up and then turned the bleeder valve out until I thought I had a fairly steady flow of coolant.

The small hose coming out of the coolant overflow tank joins the top radiator hose and when i squeeze the top radiator hose it doesnt feel taught or solid as though its full and flowing.

What kinds of indicators should I be looking for to tell if I'm getting proper coolant flow?

Thanks.

downbytheriver

Lines bled, fans still only operate when air conditioning is on.

I'm wondering if the parts house sent me the wrong temp sensor that goes in the bottom, driver's side of the radiator???

How would you test that temp sensor to know if the new one was faulty?

No check engine light anymore!! wooo-hoooo!

Now, if I could just get these fans to run when the air is off and the one to continue to run after I shut the car off.

Puzzling.

Feel free to chime in one and all!

downbytheriver

Well, bled the coolant system...took it out for a drive...

...and plowed over a deer killing it immediately.

Have now replaced the headlamps turn markers, pulled dents, sanded...sanded some more... gone to the paint shop and purchased some dupont chromacolor sapphire to re-do the bumper cover, and hood - might do the front clip too.

Had to drive 150 miles each way to find a used set of grills.

Now - I STILL have to fans the run beautifully and no fans running - no matter how warm the engine gets - when the AC is off.

No blown fuses, tested the coolant relay and auxillary relays. Replaced the one.

Replaced that temp switch in the bottom of the radiator...

I'm about to walk out there and send a few .223 rounds through the front of it if I can't figure it out.

DAMMMMMMMMMITALLTOHELL!!!!

that_tg

Did you ever get this fixed?

haraldpost

It would be a good idea to pull up a wiring diagram and use a DMM to verify wiring continuity.

haraldpost

From what I understand there are two fan SPEEDS. I am not sure if the low fan speed (AC on) implies that only one of the two fans should be running.

When the fans on my 12V 2.6 ABC switch on due to high engine temperature, they are not silent. There is a lot of air being moving around.

So when both your fans run on AC setting and you say they are silent, I'm not convinced there is anything wrong with that.