Power regulation problems...
 

I've been having problems with my 1989 Audi 200 Turbo Quattro regulating power between tasks. The car is a fairly hot running car and it needs the auxiliary fan to cool it quite frequently. The problem arises when the fan kicks in, it takes too much power to run it. There is an audible click from the dash, my volts instantly drop to just below 12v, the interior dash lighting and headlights both visibly dim and if my aftermarket deck is drawing enough power there won't be enough residual power getting to it and it will shut off completely. Is this a common problem with the 10v engine? Is the cooling fan the problem or is it the battery or the alt or is the car just heating up too much? There are many things running through my head and I need some guidance here. Any help would be great.

Re: Power regulation problems...
 

Your car should be able to support operating the radiator fan along with the A/C, lights and wipers. All the things you mention, that is, battery, alternator, fan motor and your stereo can contribute to the performance you are experiencing. I'd check that the fan's fuse has not been bypassed. If the fuse is intact, the fan probably is OK. The next easiest thing to check would be the battery. If the battery is up to par, I'd consider the alternator performance suspicious.

Regardless, why is your fan coming on all the time? If your engine runs so hot the fan comes on even when you're not idling or pushing it hard, you also may have a cooling system problem.

First, measure voltage at the fan
 

<center><img src="http://musser.us/y-ongoing/RVfiles/SearsMeter.jpg"></center><p>
These fans run at three different speeds. You can determine which speed is active at any given time by measuring the voltage at the fan motor while it's turning:

Speed 1: approx 6 Volts (draws approx 10 Amps)
Speed 2: approx 9 Volts (draws approx 25 Amps)
Speed 3: approx 12 Volts (draws approx 42 Amps)

I'll bet that your fan's speed 2 (and maybe speed 1) is kaput, so it's running at speed 3, which will suck the life out of your battery if the lower speeds aren't working.

I've found that an inexpensive multimeter with an AC/DC clamp-on ammeter is handy for troubleshooting this circuit. With it, you can determine the motor sealed bearings' condition by measuring the current drawn by the motor. (The motor will draw more current as the bearings' lubrication dries out.) Sears sells the Craftsman multimeter (Part # 3482062) in the above photo for less than $50.00. You can frequently find them on eBay for less. I use mine once or twice each month.

I suppose it's possible that your fan speed 2 circuit is working, but that the fan motor's bearings are dry (it happens with heat and time), so it's just sucking lots more current than it did when new. If so, the good news is that the fan motors are eminently rebuildable by the DIYer. (Search this forum for how to do it.)

Search this forum and sjmautotechnik for methods of determining which component (prolly the thermoswitch, a relay, or the fan motor resistor pack) has failed:<ul><li><a href="http://www.sjmautotechnik.com/trouble_shooting/cooling.html#fan">http://www.sjmautotechnik.com/trouble_shooting/cooling.html#fan</a</li></ul>

hmmm, heres my guess
 

ok, if you still ahve the fuse for the fan in place, its hasnt grossly overdrawn power. It shoudl ahve a reasonable route tot eh battery and be able to drap a TON of power without dropping your voltage below 12v. At idle the alternator isnt producing full power, but the battery should if charged and hooked up well be able to provide many hundreds of amps for short periods of time and maybe 200 amps for a while while it drains. So the fact that your fuseable 80amp link hasnt blown, would suggest that the fan isnt the real problem.

My guess is you have an alternator that is barely charging your battery, you ahve a battery that is going bad, or you ahve a wiring issue, mayeb loose connectiosn somewhere, loose ground wire, corroded connections, or the infamous line that goes though the firewall is severly corroded and causing a lot of resistance.

Try to check voltage at the battery itself, and at the posts under the hood, or voltage at the fuse panel. It shoudlnt differ by more than .2-.3 volts, anymore than that and you probably have some bad wiring.

Also, if the radiator fan itself is going bad, they generally, or so i've experienced make some noise for a while before they go, loud squeel or squeek, and if you try and spin the blade by hand it will not feel smooth. check that also.

Good luck,
Paul