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Solved: Engine back in & let's play name that problem

 
Old 12-27-2006, 06:48 PM
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MarkD
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Default Solved: Engine back in & let's play name that problem

Well, the clutch is much nicer now

I have a problem and before I start removing stuff to figure this out I am hoping someone will be able to narrow my search a bit.

Symptoms:
- Idle speed seems low and idles rough
- I give it a little gas and it misfires a bit (stumbles) then smooths out (above 2K rpms)
- Turn car off and electric cooling fan runs forever (car is not hot)

Additional info:
- Heater is not on, A/C is not on. Temp is set to blue dot.
- Wiring harness update was done (years ago)
- I suspect I have 2 problems...

Fun stuff.

I made very sure that the little vacuum lines were all connected and I am pretty certain all plugs are back where they belong.

Ideas?

Last edited by MarkD; 12-30-2006 at 03:37 PM.
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Old 12-27-2006, 06:53 PM
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Phil
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Have you driven the car yet? or just let it idle?
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Old 12-27-2006, 07:05 PM
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MarkD
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yes, let it idle for a few minutes at first... have not driven it.

One problem solved. Too much coffee.
Vacuum leaked found. It is so embarassing I don't want to talk about it. Idles excellent now.

Fan problem still there. I have seen the other threads on this but can't make heads or tails of the fix. Blower resistor may be the victim? It has been hanging around back there all nekkid for a while with other work goign on. Maybe it went south.

Here is a better description of the current problem:
No need to start car, turn key to run position and fan starts.
Temp control unit works, servos move, fans blow normally
Fan never stops until batt is disconnected
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Old 12-27-2006, 07:18 PM
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chris walrod
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Remove and reconnect the sensor on the heater blower tube, near the ballast resistor. Its a black, spring wire type connector. Try reseating it and see what happens.
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Old 12-27-2006, 07:21 PM
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Originally Posted by chris walrod
Remove and reconnect the sensor on the heater blower tube, near the ballast resistor. Its a black, spring wire type connector. Try reseating it and see what happens.
Thanks Chris, that was one of the first things I tried. You are talking about the temp sensor, right? Connector looks good. Nothing broken.

The fan now shuts off normally unless I start the car. Then it runs continously.
I am letting it run now to see if the problem is the same as other threads where it runs for 20 minutes then shuts off.

Anyone know if that temp sensor is supposed to be open or closed (when cool)?

I read 2 other threads with conflicting info.
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Old 12-27-2006, 07:28 PM
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I have seen a few cars that did this. Try turning-up the heat, then reset temp control back to cold.

Have a poke around with a flashlight underneath looking for leaks or anything not normal - and go for a drive. Bring the car back and let her idle for a few minutes and recheck the oil level. See if the fan still runs.
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Old 12-27-2006, 07:32 PM
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Originally Posted by chris walrod
I have seen a few cars that did this. Try turning-up the heat, then reset temp control back to cold.

Have a poke around with a flashlight underneath looking for leaks or anything not normal - and go for a drive. Bring the car back and let her idle for a few minutes and recheck the oil level. See if the fan still runs.
Will do when I can. All looks good underneath. Dry, clean, everthign in it's place.

Can't go for a drive right now. It's on the lift... I need to do the front susp. parts.

I am not too worried about this. The idle issue worried me since I replaced lots-o-stuff while it was out incl. plug wires. I was dreading major disassembly.
It always worries me a bit when many things are changed at the same time. You just never know what might go wrong.

It runs again. Clutch feels like buttah. It's dry, no fuel, oil, ps fluid, etc. leaks.
Life is good.
Thanks!

UPDATE: Fan shuts off after running 20 minutes. Same problem as this thread: https://rennlist.com/forums/showthre...ferrerid=35947
I don't see any answers that make sense. The CCU is very unlikely. I suspect sensor just pooped out on me? Testing it now but I am not sure if it is an open loop thing or closed loop thing. Guess I will try the wiring diagram

Last edited by MarkD; 12-27-2006 at 07:57 PM.
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Old 12-27-2006, 07:57 PM
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UPDATE: Normal condition for the temp sensor is open. Forgot I had a 964... aka spare parts

Still no joy though.
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Old 12-27-2006, 07:58 PM
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Originally Posted by MarkD
UPDATE: Fan shuts off after running 20 minutes. Same problem as this thread: https://rennlist.com/forums/showthre...ferrerid=35947
I don't see any answers that make sense. The CCU is very unlikely. I suspect sensor just pooped out on me? Testing it now but I am not sure if it is an open loop thing or closed loop thing. Guess I will try the wiring diagram
If the fan was not shutting off after 20 minutes then your problem would be transistor T1 on the main PCB inside the CCU. Your is shutting off after 20 minutes so most likely the problem is with/to/from the temperature sensor or ballast resistor. Do the front temperature mixing chambers fans work with the heat on full blast? If so, the ballast resistor should be fine. If not, try resetting the thermal switch. (see image below)

The resistance level for the temperature sensor (NTC) should be;

0'C (32'F) 28.8 - 36.4 k-Ohms
25'C (77'F) 9.0 - 11.0 kOhms
50'C (122'F) 3.1 - 4.0 kOhms

you can check this at the sensor and on pins G10 and G18 on the back of the CCU.

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Old 12-27-2006, 08:03 PM
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Thanks Jason, will test temp sensor in more detail.
Fans in front work as they should.

I tried resetting the therm switch, saw that in the other thread you posted in.
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Old 12-27-2006, 08:07 PM
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Temp sensor is at 9.8K ohms and rising as temp decreases.
Seems to be OK based on temp in my shop, engine was run, and your info above.

Sounds like I need to check wire to sensor?
That harness looked fine when I was plugging everything back in. It was tied up and out of the way until engine was back in.
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Old 12-27-2006, 08:19 PM
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Disconnected batt while I was reading here, testing temp sensor, etc. About 20 minutes total.
Seems to be operating normally now. Hmm....
The only thing I can think of would be that I let it complete the 20 minute cycle prior to the other testing. Maybe the bit that was flipped in the "brain" needed it to complete the cycle in order to read the temp sensor correctly?

If anything changes I will document it here for posterity.

All seems to be well.
Now to do the front struts/springs/sway. Yeehaw.
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Old 12-27-2006, 08:53 PM
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When you get the car buttoned back up.....take it for a 20 min. drive, this will reset the computer.
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Old 12-27-2006, 09:01 PM
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Yep, I just never heard of the fan circuit needing a "reset"... computers, bah!
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Old 12-27-2006, 10:13 PM
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Mark,

There may be something else you can check.

When I replaced the clutch last year, I had similar symptoms to what you are experiencing.

On my car, a '95, the harness recall/replacement was done several years ago. Apparently, when they did the work, Porsche specified a more "generic" harness for the car. It actually has an extra connector on the left side of the engine that is exactly the same as the connector for the blower.

I actually went down the path of replacing the resistor, since that is a pretty common problem, and no luck....

So, you might take a look and see that there is not a "free" conector lying around in your engine compartment.

BTW, I only solved this when I took the car over to Ruf in Dallas to have tires mounted, and they were able to look at my car with another 993 next to it.....

Bill
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