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Unusual heater problem - solved!

 
Old 11-08-2011, 11:12 AM
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evoderby
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Default Unusual heater problem - solved!

Hope anyone can help me out with following rather strange heater problem I'm experiencing:

*My car is LHD, the driver's side blows heat / or cold air as regulated on the CCU. The passenger's side does nothing at all, neither warm nor cold.

*Rear HVAC fan has been replaced by a cup-type tube, the relais has been bridged in order for the CCU not to go into fault mode.

*I can hear both front compartment fans running, also when placing my hand directly on top of both fan housings I can feel their electro engines running.

*When turning the controller to red (full heat) I can feel the heater hose in the passenger's foot compartment get very hot indeed.

*Both heat control servo's are 2 years old and functioning correctly, as are the 3 other servo's (windscreen/foot compartment/fresh air) although probably 20 years old now.

Again there's no flow of air through the passenger side vents (windscreen/face/side). Before taking everything apart to look for what's causing the problem, maybe someone has experienced the same before and can give some specific pointers on where to look.

Thanks in advance!

Last edited by evoderby; 11-27-2011 at 09:35 AM.
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Old 11-08-2011, 08:03 PM
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porscheforfun
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There use to be a diy on the servos to test for proper operation i would start there
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Old 11-08-2011, 08:19 PM
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Rocket Rob
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Originally Posted by porscheforfun View Post
There use to be a diy on the servos to test for proper operation i would start there
http://porsche964.co.uk/technical/servos.htm
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Old 11-08-2011, 11:50 PM
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tbennett017
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dumb question, but is the vent open at the dash? (turn the wheel to open them)?
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Old 11-09-2011, 07:03 AM
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Thanks guys,

As mentioned all the 5 servo's are operating correctly, this was the first thing I checked since I initially also thought the problem to be servo related.

The dash vents are open......I was feeling rather ashamed at the thought of them being closed, then I realised the windshield demister also wasn't giving any airflow on the passenger side.....then I checked to make sure, they're open alright! No such thing as dumb questions....thanks for the suggestion ;-)
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Old 11-09-2011, 07:13 AM
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Bertrand
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I once had the plastic part that connect the heater tube to the mixing chamber (through the firewall) disconnected.
That could explain.
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Old 11-09-2011, 08:32 AM
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there are no unusual problems with our vent systems! They are all normal problems
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Old 11-09-2011, 09:52 AM
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evoderby
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Thanks Jim, that's what I told the GF when she complained about her side of the windshield getting all foggy....she doesn't seem to agree;-)
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Old 11-09-2011, 10:04 AM
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Originally Posted by Bertrand View Post
I once had the plastic part that connect the heater tube to the mixing chamber (through the firewall) disconnected.
That could explain.
Thanks Bertrand, I'll look into this although in theory this should only effect warm air (or lack thereof) being blown through the vents, wheras I am also experiencing no air being blown through the vents when set to full cold....

I think I'm going to have a look inside the fan housing this weekend to see whether the fan blades are in fact attached properly to the motort and all trap doors and associated connecting rods are functioning as they should....

....sometimes I wish I had simply bought a Deawoo;-)
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Old 11-27-2011, 09:56 AM
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Decided to go all the way and remove the heater unit for a complete functionality check.

After removing the fuel tank and bulkhead panel I had good access to the driver side fan cover....guess what, this fan was not moving freely at all. A quick lube to get it going confirmed that I had airflow once again on the passenger side...

...sub conclusion: drivers side fan provides passenger side airflow and vice versa (which contrary to what I first intuitively had thought).

I decided to press ahead and remove the entire unit to give it a thorough cleaning, check
all internal flap etc. and give the bearings of both fan motors a good soak in WD40...followed by teflon oil until fully saturated. Both are now spinning freely like there's no tomorrow ;-)

After having put everything back together my heating is working again like new, with a nice and steady stream of air coming from the blowers!!

I have to say the job has taken quite a bit of puzzling at times (nice diy by Wachuko was very helpful, Thanks!) but very rewarding in the end....
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