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Steve Brookes

Steve Brookes

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The last case I saw where the front fans stayed on all the time was caused by a faulty final stage relay (the module under the scuttle panel with a big aluminum heat sink). I would start by unplugging that and putting your main fuse back in and see what symptoms you get. Hopefully, your rear blower will then stop running when the key is out (I believe you've already changed the NTC sensor which is the usual cause of the rear blower staying on) but will work when the engine is running and help pass some air from the rear cooling fan through the heat exchangers and dilute that smoke. I can't say I'm sure this will work because like many I find the 964 HVAC system very difficult to understand and trouble shoot. However, I do think that you need to solve this problem of fans running all the time rather than pull fuses to stop them.
 
Hi all

During the last 2 months that I have been driving my car, if I go for a long drive and really warm the car up, on my return I find light smoke coming out of the boot vent and from the drivers side wheel arch. AT first I thought it might be oil that may have been spilt during the service that was burning off. However this has not passed, and yesterday following the drive home from the Harewood House show my daughter also found that the bolt on her lap belt was red hot, as well as the light smoke.

Currently my heater fuse is out as both front and rear blowers are on constant even when the key is removed. Therefore I also get hot air into the cab from the windscreen vents during driving (windows open or roof down always)

Is my smoking issue related to having no rear blower in use?

If not help please.

regards lee
 
Hi Steve Thanks for your reply. I will try unplugging the final stage rely and see what happend, in fact I have managed to pick a spare one up very cheap so I will have a play around and see what happens. I will re post when i have done some checks lee
 
Hi Steve My car obviously does not have aircon, what effect would a CCU without aircon, but a different part number have? Someone has offered me one to try but my part number ends in 046 and this is 049. Is it worth trying or am I just wasting my time? lee
 
I presume you want to see if the CCU is the reason for your fans always being on? In which case you could simply unplug your CCU to see the effect. This was done in the case I mentioned above and the front fans continued to run i.e. the CCU wasn't at fault (it was the final stage relay). Regarding your question, I can't see why the air con version (048) wouldn't work on a non air con car if you want to give it a go.
 
Hi Steve I plugged in the new ccu today which does have aircon on it. As soon as I plugged it in the small fan on the back started spinning (which I understand it should do). when I put the ignition on front and rear fans switch on. If I turn the speed control knob - that works. Both fans then stop when I turn the ignition off. I need to check it on a run to see if it has had any effect on the constant heat into the cab and to see if the rear fan runs when I shut off to help cool the engine and then stop when the temp drops. Is there anything else you can think of, or what other effects should I get from the sliders on the ccu etc. cheers lee
 
Sounds like you have found the source of the problem. The little fan on the back should run all of the time. You can try cleaning it to see if you can get it to work: http://forums.rennlist.com/rennforums/964-1989-1994-911/211207-how-to-fix-a-squeaky-ccu-fan.html However a non-working little fan shouldn't stop the CCU working (it just works more effectively with the fan running). Also try vacuuming out the aperture that the fan plugs into. The rear fan should stop running when you move the CCU knob to the blue dot. The front fans should run in very low speed even when speed is selected to 0. But from what you say they work fine with the new CCU (which also means that the final stage relay is OK). All fans should stop with the ignition off but this can sometimes take a few minutes. The sliders operate servos under the scuttle panel. More information about the servos here: http://porsche964.co.uk/technical/servos.htm I would double check that your old CCU is no good by trying it again. If you're lucky you may find that it just wasn't doing its job because it wasn't plugged in properly or the action of undoing it freed up a bad connection. If it still doesn't work it means finding a replacement CCU.
 
Hi Steve Decided to sell the Aircon CCU and then buy the correct part number for my car (without aircon), so i will update once I get that sorted. i have managed to work out why the car is smoking, after looking under the offside rear arch I noticed a leak which is getting onto the silencer. Another job now on my to do list. Lee
 
ORIGINAL: l.chadburn i have managed to work out why the car is smoking, after looking under the offside rear arch I noticed a leak which is getting onto the silencer. Another job now on my to do list. Lee
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Smoke from the arch and boot lid has aflicted more than one of us. I had it in the past and saw it on a friend's car recently when he took it on its first track day. i.e. you get the smoke when the car gets really hot. It's often caused by oil on the top of the engine coming from a leaking oil pressure sender O ring or the breather pipe next to it (they harden over time and cause the leak). The oil funnels its way down the side of the engine and drips onto the exhaust. Even when you identify the leak there's still plenty of old oil lying on the top of the engine to still cause the smoke. You can see from this pic of my top air cowling how much old oil was lying around:
SDC10918.jpg
 
ORIGINAL: l.chadburn Hi Steve Decided to sell the Aircon CCU and then buy the correct part number for my car (without aircon), so i will update once I get that sorted. Lee
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You've confused me now! [:D] Do you mean that yours is an Aircon CCU and the one you borrowed that fixed the fan problems is a non Aircon?
 
No otherway round. I have a cabby with no aircon. I tried an aircon unit in it. sorry for the confusion. lee
 
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