Bill Ball

Hi all:

As part of Konstantin's Murph Stage 1 install, I have 4 small fans that Murph provides wired in parallel to the Fan 1 lead and a 16" auxiliary pusher fan to the Fan 2 lead. Yesterday they all operated OK in the garage, tested by pulling the air temp sensor leads on the top of the intake manifold.

Today I found the auxiliary fan not working and fuse 30 (Fan 2) blown. I replaced the fuse.

None of the fans work when I pull the air temp sensor or push the AC button. All the fans run when I disconnect the lower radiator temp switch, which I gather is like an emergency override.

The auxiliary fan seems to draw too much power for Fan 2 power supply (although possibly I just shorted it) and the 4 small fans are not completely happy on Fan 1 circuit. Even if I disconnect the auxiliary fan, the other fans do not run in response to the air temp test or AC button. They did run before when I had the 4 main fans split into pairs on the two fan circuits with no auxiliary fan.

I'm thinking of switching the 4 fans back to be split over Fan 1 and 2 circuits and wiring the auxiliary with a direct power supply from the charge post controlled by a relay driven by the Fan 2 circuit. Will the fan 2 circuit be able to trip the relay? I ask because the circuit does not provide 12 volts AFAIK.

Any advice on the wiring? I'm electrically challenged. Any other ideas?

Kevin Michael

Bill, same for me when I first installed. Believe it or not I only have two of the muffin fans in the car now. The big Spall fan up front works harder than all 4 of those together. The muffin fans run SLOOOOW when you daisy chain them. I repositioned the muffin fans to one per bracket, running them on the secondary. Then the front (spall) is on the primary. Runs nice and cool. Hard to believe when I told you about that hotspot in the center of the rad and the big fan would cure it huh? Glad to hear your getting K's car staightened out! He's a nice guy.
Kevin

hacker-pschorr

I'm using the same four fans off a 30amp relay & 30amp fuse straight off the jump terminal. Mine are turned on using a manual switch in the cabin.

On Shane's car I installed a 2-way switch in the radiator replacing the factory 1-way switch. This keeps the front fan working as stock, turns on the rear fans at whatever temperature the switch is rated for. These switches are standard Audi / VW so there are many choices to pick from.

I also have Shane's fans powered via a 30amp relay / fuse off the jump post.

Kevin,
If I were you I would rebuild your radiator. On Shane's carn (and mine) the four fans are more than enough. It's funny how every hot running 928 people look at the fans.
With a healthy radiator, fans are almost not necessary.
I was driving around town in 95+ degree weather testing my cooling system. Unless I was stopped at a light longer than 20+ seconds, I didn't even turn my fans on. This is with the stock thermostat.

shaaark89

bill,
my front fan is wired to a temp probe in the radiator and has it's own power supply and relay/fuse off the jump post. the rears are wired as you initially did them. you can get probes that come on/shut off at various temps. works very well.

Kevin Michael

Doesn't Shanes' car have the factory front fan still in play? Also I'll take note of your radiator suggestion. I guess since my car always ran cool before my SC, which then it overheated, Reconfiguring and adding the front pusher brought it back within spec. This is why I don't suspect the radiator. That and it's only 2 yrs or so old. But anything is possible with these cars! You say you can ride around with no fans and you don't overheat? I want whatever radiator you have!

Larry928GTS

The fans are supposed to come on when the leads for the temperature sensor on top of the intake manifold are shorted together, not by just having them disconnected from the sensor. Shorting the leads together simulates high temperature.

Larry928GTS

When I bought my S4, there was a previous owner's mechanic wiring problem related to the fans. I didn't find out about it until the initial trip home with the car. I drove it probably around 3,000 miles with no fans almost that whole time, and only one fan for a very brief part of that time. Stock radiator and thermostat in the car at the time, and the only time the temperature would get up high enough to get close to the warning light coming on was when stopped and idling for a while, like Hacker mentioned for his car too. The car was from the south, and had a higher percentage of water to coolant than the usual 50/50 mixture, which may have helped some.

Tim Murphy

I suggest wiring all four fans together, in parallel, and run them off the primary fan circuit. If this does not work, you have other electrical issues.

The front fan should run just fine off the ac/secondary fan circuit. There is no way the aftermarket fan is pulling 30 amps. Is the AC turning on with the AC button depressed? Do you get 12 volts to the secondary fan plug with the AC button depressed?

Kevin Michael

I may have those electrical issues Tim speaks of. When I ran those fans like that they were very weak.

hacker-pschorr

Yes, but it only came on with the A/C while I was testing it.
As long as I stay moving, even at 25-30 mph. If I sit at a light for a bit I see the temp gauge start to climb, then I turn the fans on.

My car ran without a front fan until last year. I only added it to move more air through the A/C condensor, not because I needed it for engine cooling.

Droplink

Remember that the ingredients in coolant also help with boil-over (i.e. raises the boiling point). So a weaker mixture could also reduce its ability to handle higher temps.

hacker-pschorr

Too much coolant can also hurt performance.

Most track cars run 95% water with 5% water wetter or some other additive.

Droplink

Agreed, too much can also hurt. But 50/50 is usually recommended for most street cars.

I beleve track cars use less coolant for two reasons:

1. Water will evaporate and is less slipery if it leaks out on the track.
2. Water has great thermal transfer properties - I don't think Ethyl-glycol is as efficient

aggravation

Probably a stupid question but...you do have the hood switch pressed down, right?
Mine don't run unless that switch is closed....

Bill Ball

OH! OK, maybe things are OK then.