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Driver's side cooling fan Inop--FIXED!!!

 
Old 04-23-2010, 10:53 AM
  #16  
DanielD
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The wiring is good from the amp to the fans. There is no physical damage to the harness on the driver's side. I've hooked an ohmeter using spade connectors on the plug eng and wiggled, pulled, slapped around the harness with the ohmeter connected with no fluctuations on the meter; solid continuity.

leadfoot, I've checked around and no one seems to have the BUZ11A MOSFET. Probably out of production now.

For now, I'll move on to my LH airbag sensor high resistance issue. Hopefully that one will be a bit easier to rectify. I'll continue my search for the mosfet. I'll eventually find one.

Thanks for all the input. This forum rocks!!
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Old 04-23-2010, 05:03 PM
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Originally Posted by DanielD View Post
The wiring is good from the amp to the fans. There is no physical damage to the harness on the driver's side. I've hooked an ohmeter using spade connectors on the plug eng and wiggled, pulled, slapped around the harness with the ohmeter connected with no fluctuations on the meter; solid continuity.

leadfoot, I've checked around and no one seems to have the BUZ11A MOSFET. Probably out of production now.

For now, I'll move on to my LH airbag sensor high resistance issue. Hopefully that one will be a bit easier to rectify. I'll continue my search for the mosfet. I'll eventually find one.

Thanks for all the input. This forum rocks!!
I took that MOSFET number with me to the parts store and found an equivalent service part. The ratings all consolidate up, so new ones are better than old. I had to drill and tap holes in the heatsink to mount the replacements after drilling off the original pins. Also, be sure to get a tube of heat sink compound for buth the FET-to-heatsink and heatsink-to-case junctions.
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Old 04-23-2010, 06:12 PM
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Should both fans be running post drive on cooldown? If so I've "caught" mine running badly.
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Old 04-23-2010, 07:18 PM
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Originally Posted by fraggle View Post
Should both fans be running post drive on cooldown? If so I've "caught" mine running badly.
The will run on cooldown if either the temp switch in the top of the intake is hot, or the ATF temp switch in the auto trans says too hot. I'm not sure how running the fans cools the trans when it isn't pumping, but there is a function for that anyway. When either of these switches is engaged, the fan runs at low speed.
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Old 04-23-2010, 07:22 PM
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The "fan" or the "fans". Low speed is verified. Sorry if this is in the manual, I'm on my blackberry so don't have it at hand.
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Old 04-23-2010, 07:49 PM
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Originally Posted by fraggle View Post
Should both fans be running post drive on cooldown? If so I've "caught" mine running badly.
Just to be clear both fans should always be acting the same as each other. Other than that see DrBobs reply.
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Old 04-24-2010, 04:42 PM
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I chased an inop fan for months, as had the PO, who got around it by running a relay off the powertake-off in the engine bay. I did not like that so went back to basics to trouble shoot it. I took the fan controller apart and found some capacitors with corroded legs, fixed those and it still did not run. I replaced the mosfets and took aout and tested each transitor, resistor and diode. So many hours!

I got the controller to work but then shorted it when I put the back on. In the end I got a replacement but that did not fix the fan. To cut a long story short, it was the fuse holder which had lost its grip on the fuse. The fuse would not blow, but would get too hot due to poor connection and increased resistance. The fuse would sag out of the little copper jaws. I replaced those and its been working fine for 4 years now.
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Old 04-27-2010, 11:27 PM
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Here's an update.
I swapped out the fan amplifier with known good. Same problem. Checked the power to the fan amp for fan1 and fan2. Power is good as I jumpered power at the fan amp plug straight to each fan and each fan works fine connected to power through its appropriate fuse. That eliminates the power to each fan, ground to each fan and the associated wiring.
ARGH, frustration is mounting.
Wierd thing: I can swap the signal pins at the controller and the only fan that runs is the driver's side fan. I believe its pins 6 and 8 that are the signal pins.
Any ideas? This one is starting to get to me
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Old 04-29-2010, 05:00 PM
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bump...
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Old 05-23-2010, 06:25 PM
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OK, changed out the MOSFETS on for the driver's side circuit in the fan amplifier. Still no worky...
Anyone know an exorcist???
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Old 05-28-2010, 04:43 PM
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I have also a non working fan on drivers side.
Read all through this post and I feel like leaving it alone (but I don't).
I think first thing to do for me is to examine the MOSFET issue.
My fusebox looks OK so a loose connection would be not the first thing I would look for.

Somebody told me that Porsche could program the whole system differently for different regions.
Are we 100% sure the two fans sould ALWAYS operate at same time or does the 2nd kick in at higher temps on cars with alternative program ?????


Thanks,
Paul
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Old 05-28-2010, 05:37 PM
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Everything I read on the subject states that the 2 fans should run at the same times... I had a fluke the other day after I moved the wire harness a bit. The driver's fan worked for about 2 hours. Then back to the same old problem. I'm sure its a wire. I'm thinking it the signal line from the controller to the fan amplifier. I'm going to work on it this weekend and will update with any results.
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Old 05-28-2010, 05:41 PM
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I read 5 and 8 as the power pins or am I reading this incorrectly?
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Old 05-29-2010, 12:54 AM
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5 & 8 are the power outputs to the fan motors. They are controlled by 7 & 6, the pulse width modulated signals from the controller next to the passenger seat. 1 & 4 are the 12 volt supplies from the power fuses to each fan.

Last edited by DanielD; 05-29-2010 at 12:56 AM. Reason: Clarification
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Old 05-29-2010, 01:57 AM
  #30  
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Originally Posted by DanielD View Post
5 & 8 are the power outputs to the fan motors. They are controlled by 7 & 6, the pulse width modulated signals from the controller next to the passenger seat. 1 & 4 are the 12 volt supplies from the power fuses to each fan.
OK, so why did you swap 6 and 8?
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