that_tg

I got this idea from a write-up on this forum but I have been searching for it and can not find it. I bought the same fan as the poster did and am now almost ready to do this conversion.

Here is the link to the fan

He had wired the fan to the smaller electric fan so it would go on when that one did. I am looking to go a different direction and have the main fan turned on with a coolant temp switch. Now, I am not sure how to do this. I am looking at this.


The kit has the temp sensor. I have that positive terminal from the battery near the right front wheel for power but am looking for help or ideas for getting the switch working. Any ideas are welcome. I have not bought the wiring kit yet so if you have a better idea I am open to it.

I plan on documenting my procedure to help others in what to or not to do.
Please help with some electrical how to. Thanks.

Razman

I admire your bravery and look forward to the outcome.

hillpc

Using that wiring kit, this should be simple electrically. The temp switch when it gets hot sends power to the coil of the relay (through the thin wires), which then pulls in the contacts of the relay. The contacts of the relay send power to the fan through the fat wires, from some place on your car (under the hood? exact location to be determined) that has lots of +12V current available to power the fan without blowing an Audi fuse. That terminal you spoke of sounds ideal, if it's protected from rock damage, etc, and you can protect the wiring from same. Just make sure the fan harness has a fuse in it. This is similar to how a starter solenoid/relay or horn relay works. (On an old US car, the coil circuit for the starter relay is powered on by +12V from the ignition switch, while the coil circuit for a horn relay is powered on by a ground coming from the horn switch; the +12V side is always connected.) Also need a place to hook a fat ground wire. You also need to find a place to install the temp-activated switch that screws into some water passage somewhere to sense the coolant temp. (You have this scoped out yet?) I can give you more specific wiring details (colors) if you post the wiring harness instructions. The wiring diagram on the relay could also help, but it may not have colors on it. I also can't speak to the adequacy of the airflow from that fan compared to the stock fan. (Did the other guy say it was OK?) I suspect the cfm (cubic feet per minute of air moved) ratings don't tell the whole story, since the actual cfm will change depending on how thick the radiator + condenser is, and how tightly the fins are spaced.

Y888

Whats better Mishimoto or Spal?

that_tg

Where to put the temp sensor is the big question. I am confident in getting the positive to the fan. I also have heated washer fluid installed under the right headlight, next to the washer bottle. Took a large gauge wire from the terminal near right front tire up to the heater. That heater has an inline 60 amp fuse. Will tap onto that wire. It is rare that I use the heater spray but will be careful to not use it when the fan is running just to be safe.

Thanks hillpc for all the info on the wiring. I am more confident doing this knowing you are available.

Back to the big question. How do I get this temp sensor to read the temp of the motor? What about a sensor that fits in the fins of the radiator? Not my first option.

Not sure about Mishimoto or Spal. The other guy used Spal so I am going for it.

audinutt

quattroworld.com Forums: Okay here are some more details on what/how I did it. A8 Electric fan conversion * revised video *

that_tg

Well, searching the wrong forum would be the reason I could not find it. Thanks!


How was it this summer?

Any new tips now that you have driven with it for sometime?

that_tg

Am still hoping audinutt will give some feedback on how it handled the summer. Sure it worked great.

Here is my next idea. Radiator temp probe. Turns the main fan on and off with temp. Also has an AC override. might not use the ac part.?

What do you guys think? Has anyone tried this before on any vehicle?

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twentysevenlitres

Audi have put a perfectly good temperature switch in the radiator for you in the form of the trinary switch.
I can't recall the pin outputs, but there's a lower temp output and a higher temp output, which correspond to different fan speeds from the auxiliary fan.

Tapping into the lower temp output from the trinary switch is your best bet, as that will be closest to the thermostat opening temperature and will reduce the chance of overheating.
Just remember the trinary switch is likely -ve switched, so you'll have to be use it to earth your relay. It's also up to you where you source your power from to power the trigger side of the relay, but most switching (including ignition/accessory switching) on an Audi is -ve, so you may end up with standalone wiring.

If you want the relay to be triggered by ignition and aircon switching, use the auxiliary fan wiring from the resistor output. This will still use the lower temp output from the switch, but will also run with the aircon, just as the aux fan currently does. Don't worry about any lower voltage output from the resistor, 9 or 10V is plenty to trigger a relay. You could even tap into wires at the aux fan plug.

If you insist on using the independent temp switch, the best place to mount it is on the radiator side of the thermostat, probably in the tank (funnily enough where the trinary switch is mounted!).
That mounting plug that comes with the temp switch kit may be able to cut its thread into a suitably sized hole in the rad tank. I would seal it with a high quality plastic/rubber/metal glue like Loctite 438 as well.

If that power junction under the wheel arch has come from the battery, it should be good for a few amps. Just use high quality wire and good earth's.


Have I done this before? Yes I have (but not to an Audi)!

audinutt

I can report it worked fantastic all summer long. The only thing I do want to change is to add a resistor to get low and high speeds for the fan. I will be doing this most likely when I tear the front end apart to do the timing belt service.

-Richard