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951 No heat!

I have absolutely no heat in my 951. new car for me so I don't know when it failed. The A/c has been removed at some point if that helps.

I have searched all over, but every thing I see relates to heat ON all the time. I have found nothing on no heat at all, except for possibly bleeding the coolant. It seems to me that this would cause poor heat, not no heat at all. I have also tried to manually operate the vacuum valve (which doesn't seem to operate on it's own), but it doesn't help. As I understand it, it fails to full heat anyways.

I have also checked all fuses etc, and the fan works fine.


Any ideas? It's getting cold here in Canada!

Paul
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Old 10-07-2010, 04:22 AM
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Try bleeding the cooling system again, and make sure you turn the heat FULL on when you do, usually a no heat situation is caused by air trapped in the heater core during cooling system bleeding.
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1989 944 S2 Alpine White T-Boned (totaled) by a lady dressed in a CLOWN costume (RIP ) Apr 89 - Mar 08
1988 944 Turbo S Silver Rose Metallic, K27/6, Vitesse MAF, Tial 38mm DP WG
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Old 10-07-2010, 05:50 AM
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Check the fuse for the climate control in the underhood fuse box. Mine was blown and I had a no heat situation. If that checks out OK then check the plastic connector under the dash drivers side for the heat control flap/motor.
Old 10-07-2010, 10:33 AM
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There is a vacuum heater control valve which opens to let hot water into the heater core.....it's either by the firewall behind the intake or just above and behind your oil filter next to the engine.
The vacuum line which opens this valve is controlled by a vacuum sylinoid which is in behind the glove box.....it is identicle to the sylinoid which controls the a/c flapper so it could be swapped if its still there since tha a/c was pulled.

Find the heater valve and see if you have vacuum at it when the heat is on, if not track down the sylinoid and see if it's opening when you turn on the heat.
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Old 10-07-2010, 06:03 PM
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Ok, I have some things to chase down now, Thanks all! i'll let you know.

One question Bell, I thought the vavle failed to full heat. As in, it is normally open. Is this not the case? The valve doesn't seem tho operate, but if I manually operate it, there is no change in the heat in the cabin.
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71, 79 Targa (both sold)
75, 87 Coupe (both sold), 90 C4 Coupe (tree won...)
73T Targa (current) 2.7, fast, fun, fly!
88 951 (current) slightly modified ;-)
Old 10-07-2010, 06:29 PM
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With no vacuum (heat turned off) the valve is closed , hence when you bleed 944/951's you need to turn the heat on.....all other german cars default to full heat (bmw's/mb's).....
Get it up to temp, and open the valve manually, it'll take about 15-20 seconds to feel full heat.....
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Old 10-07-2010, 06:45 PM
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The on going saga...
when i dug into this yesterday, I noticed that other than the fan, nothing works. None of the solenoids or motors function (i.e. shifting heat to footwell, fresh air mix..), although the fuse is good. If I disconnect the clip to the heat "flapper" in the driver's footwell I get heat, but of course can't regulate it, other than to turn the fan on or off. Om that note, the fan works on "4" only, which seems to be a new development since I manually opened the flapper. Can't be positive of this though, let's face it, I have had the car a month, and only noticed the heat problem when it turned cold last week.
I'll go through the wiring diagrams (again), but I am pretty well stumped. The only thoughts I have are, 1) when the A/c was removed was there some connection that should have been bridged? and 2) I don't see an "outside temp sensor" up near the nose of the car. If this was missing would it break the circuit?
TIA
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71, 79 Targa (both sold)
75, 87 Coupe (both sold), 90 C4 Coupe (tree won...)
73T Targa (current) 2.7, fast, fun, fly!
88 951 (current) slightly modified ;-)
Old 10-10-2010, 02:03 AM
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When the blower is turned on high (4) it bypasses the resistors which reduce the fan speed, these resistors are in the blower assembly under the hood, they look like 2" long coils and are atatched inside the assembly, could just be unplugged? The plug is on the driver side of the assembly iirc.
If the blower works on high then you have power, the control panel sends a signal to the solinoids which then controls the flappers, I would find the solinoids, make sure you have vacuum on the input side, then check at the plug that you're getting signal to turn it on when on heat...
If no signal to turn on get into the control panel, chances are you have signal since the blower is turning on.

If the 2 resistors in the blower assembly are bad or unhooked you will not have the slow speeds on the fan, one side of the resitor will show a full 12v and the output side will be reduced voltage if working properly.
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Old 10-10-2010, 09:13 AM
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The resistors for the blower have built in thermostats to prevent overheating if the air flow is obstructed. There is considerable I**2*R heating at blower speeds < 4 so the incoming air is used to cool the resistors. Clean the thermostats with electronic cleaner.
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Old 10-10-2010, 10:18 AM
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Hello Paul, Check out the link below. It will tell you all about the Heater and location of each unit. You need to start looking at Clark's Garage.com for all your Maintenance help. We all use it, I know it has helped me out.

944 HVAC Operation and Malfunctions

Clark's Garage Shop Manual Index

Cheers,
Larry
Old 10-10-2010, 12:38 PM
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I am having the same exact problem on my 85.5. I pulled off the connectors to the flapper and the footwell motors and found there is no power there at all. Fuse is OK. I will be digging into this electrical problem next weekend.
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Old 10-10-2010, 07:37 PM
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Dave,
Sorry to hear that, but please keep me posted. I'll do the same, but don't know if I'll get around to anything this week. If you need heat the temp fix of disconnecting the flapper clip in the driver's footwell works well. Actually a little too well. Went for a country drive, and had the windows open and the sunroof off. Still a little warm in the cabin.
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71, 79 Targa (both sold)
75, 87 Coupe (both sold), 90 C4 Coupe (tree won...)
73T Targa (current) 2.7, fast, fun, fly!
88 951 (current) slightly modified ;-)
Old 10-11-2010, 01:15 PM
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Still no heat, but have been replacing blown head gasket, so not a lot of time to worry about heat
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Paul
71, 79 Targa (both sold)
75, 87 Coupe (both sold), 90 C4 Coupe (tree won...)
73T Targa (current) 2.7, fast, fun, fly!
88 951 (current) slightly modified ;-)
Old 10-25-2010, 01:41 PM
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Hi Paul,

I have not had much time to dig into this beyond checking fuses again and pouring over the wiring diagram. I will be in Germany until next week so won't have time to dig in until then. Too bad as it looks like snow here in Minneapolis soon.

I will keep you posted with what I find.

Best regards
-Dave
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96 C4 Cab, 85.5 944
82 SC Targa SCWDP #0023
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Old 10-26-2010, 06:10 AM
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Success!

OK back at the heat issue this spring. I strongly felt that when the PO had removed the A/C something else had been "disturbed". So a complete visual check and all looked good. The factory manual has a pretty good trouble shooting guide which, combined with the Clark's garage write-up, leads you through tests on the electrical and vacuum components. "Unfortunately" all looked good!
So I did what I had been avoiding doing; I removed the control unit from the dash. I had avoided this up to now for 2 reasons: 1) these old plastic parts often break when popped off, and 2) If I needed a new control unit, I would probably just continue to manually adjust the heat with the under dash flappers. It is after all a summer car.
guess what? when the control unit came out, the connector at the back had popped off! A quick reconnect and reassembly and all works beautifully!

So being a trained troubleshooter, following procedure cost me about 2 days of work. If I had of just started messing around I would have been done in a couple of hours.

Oh well, I am now an expert on the 944 heating system.

Paul
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Paul
71, 79 Targa (both sold)
75, 87 Coupe (both sold), 90 C4 Coupe (tree won...)
73T Targa (current) 2.7, fast, fun, fly!
88 951 (current) slightly modified ;-)
Old 04-23-2011, 12:46 PM
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Great news Paul! I am happy to hear you are up and running again, so to speak.

I have been ignoring the heat issue as I am trying to get my clutch job done. Due to one thing and another it has taken me all winter to be close to done. Anyway, I have been avoiding tearing into the dash as I felt that was my next step. Now I have hope.

Thank you for updating the thread.

Best regards,
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-Dave in Minnesota
96 C4 Cab, 85.5 944
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Old 04-23-2011, 08:58 PM
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If you go to this site, starting at page 436 of the pdf there is a good trouble shooting guide:
http://www.mikepellegrini.com/Porsche/Porsche%20944%20Shop%20Manual%20-%20Vol3-chassis.pdf
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Paul
71, 79 Targa (both sold)
75, 87 Coupe (both sold), 90 C4 Coupe (tree won...)
73T Targa (current) 2.7, fast, fun, fly!
88 951 (current) slightly modified ;-)
Old 04-24-2011, 04:57 AM
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Just for the record, I have solved my problem. I finally figured it had to be the climate control console as I had fan control and the AC and defrost switch worked but there was no juice at all to the flapper solenoids. Replaced the climate control with a known good used unit and everything now works. Thanks for all the support.
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96 C4 Cab, 85.5 944
82 SC Targa SCWDP #0023
82 928
67 912 60 T-5 B Cabrio
Old 06-01-2011, 04:15 AM
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