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no heat - at all

Hello all. I have been perusing the forum to see if I can save myself some time and money chasing down no heat on my 86 944.

I have only had it a few months, but it has never had heat. I suspect the plastic clip is fine since I am getting no heat, and would get heat all the time if that clip was broken, correct.

Also, if the heater control valve was broken it would be stuck open as well giving me heat all the time.

I have seen some posts about the air temp sensor in the dashboard, and that may need some investigation, and maybe a vacuum line re-check.

Am I on the right track, and is there anything else to check. Pretty sure my coolant level is fine, and don't suspect any coolant leaks or air, but again, I have only had it 9 months or so.

THanks in advance.

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85 Mercedes 300cd sold
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02 325i sold

86 944
Old 10-24-2020, 06:06 PM
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Going to follow this, as I have the same issue.
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86 Porsche 951
'69 Ford F100
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'17 F150
Old 10-25-2020, 05:50 AM
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Have you properly bled the cooling system?
Is the engine getting up to temperature?

There are all kinds of wild ways to bleed the cooling system but it's not really hard to do it the normal way. My quick way is to blow coolant up to the bleeder via the overflow hose. But just parking pointed uphill with a hot running engine and releasing the air from the bleed screw should also be just fine.

If the engine isn't getting properly hot you won't really feel heat either.

Beyond that, checking the operation of the heater valve, vacuum signal to the heater system, etc. is in order. But that should default into heat all the time and not no heat.
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1987 928S4
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Old 10-25-2020, 07:12 AM
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Hi,

I would start by warming up the car and turning the heat on full. Follow the heater hose coming off the back of the engine head. Feel for heat all the way from the head around the heater valve, to the heater core and the return hose. All these hoses should at coolant temperature.

If the hoses are all hot, you have a climate control box problem. If the hoses are cold you have a heater water valve problem or a general cooling system problem. If this is the case, check the vacuum control to the heater valve.

At any rate, I would not dive into the climate control box until you know it is getting hot water.

Good luck, Peter
Old 10-25-2020, 07:27 AM
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Ok, thanks.

I don't have a lot of time to research or read at this time. Will try to crack it next weekend.
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85 Mercedes 300cd sold
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02 325i sold

86 944
Old 10-25-2020, 05:00 PM
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http://www.944time.com/porsche/images/2009-porsche-944-heater-control-valve.jpg



Warmed engine up. upper radiator hose and lower radiator hose got hot, it seemed the hose at the heat control valve was getting warm, but i need to double check. I tried prying the heater control valve open (i am assuming that like in the picture mine is the closed position since i dont seem to have vaccuum). mine stays like in the picture, and i can push it back in and hold it with a screw driver, but no hot air was coming into the vents in either position. Fan speeds all work fine. the cabin temp hose was techincally just pushing against that hole in the dash trim, but I guess that is all it does.

I did check all hoses and fittings, and everything seems to be ok, although i found my thermo valve fitting only had one hose on it, and one MIA, i saw where that feeds from the throttle body area but my entire hose seems to be removed and one of the two fittings is uncovered.

lastly, i don't seem to be getting enough vaccuum or the HVac Head unit is failing, as the recirculating button does nothing, the flaps stay open in the fresh air mode and don't move. Should I be looking at replacing the climate head unit, if I am getting warm hoses at the heater control valve?
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85 Mercedes 300cd sold
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02 325i sold

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Last edited by spugeddy; 10-31-2020 at 02:24 PM..
Old 10-31-2020, 02:19 PM
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That pic is of the open (heat) position, the valve sucks closed. If you don't have heat maybe you need to bleed the cooling system.

Lack of vacuum to the CC head is usually due to a bad vacuum connection in the battery area. Or maybe closer to the engine.
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1987 928S4
1992 968 cabrio
1994 968 cabrio - Supercharged
Old 11-01-2020, 08:22 AM
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Like I said, I’m in the same boat, but for help troubleshooting, you might try a mighty vac on the valve. It will allow you to open the valve manually and see if you get heat.
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86 Porsche 951
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'17 F150
Old 11-01-2020, 08:25 AM
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Quote:
Originally Posted by cfassett View Post
you might try a mighty vac on the valve. It will allow you to open the valve manually and see if you get heat.
Negative. No vacuum = open = heat. It's for safety, if something goes wrong you can still defrost.
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1987 928S4
1992 968 cabrio
1994 968 cabrio - Supercharged
Old 11-01-2020, 09:27 AM
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Ok, yeah it looks like the heater valve is in the open position and by pushing it back into to the diaphragm side I am "closing it", so there is heated coolant on both sides of the valve.... super hot, but no heat in the cabin.

Does it go into the heater core unit below the fan cage next, and does this sound like a head unit problem then... or blockage going into the heater core?

Any advice. I spent about 4 hours yesterday on it, and getting discouraged!

Also, I need to track down the vacuum on the flap lines, as they don't seem to be operating the open and close when pressing the button inside. Is the brake booster assembly a common replacement item.

Sorry for all the noob questions. This is the second oldest car I have owned. The other was a W123 Mercedes diesel, which is famous for durability.
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85 Mercedes 300cd sold
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Last edited by spugeddy; 11-01-2020 at 02:53 PM..
Old 11-01-2020, 02:51 PM
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Can you describe how you bled the cooling system?
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1994 968 cabrio - Supercharged
Old 11-02-2020, 04:22 AM
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i haven't bled the coolant ... yet....

but do you think my problem is caused by air in the system? I know i am getting circulation via the upper and lower radiator hose, plus hot rubber hoses on both sides of heater control valve, and the return line is also hot.

I am willing to try it, but can't wrap my head around why that would be causing this issue based on my symptoms and what i found by removing stuff and poking around some
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98 323is sold
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Old 11-02-2020, 03:50 PM
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I'm wondering if the PO had a leak and plugged the heater core and just bypassed it...
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Old 11-03-2020, 06:20 PM
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If so, that should be obvious, looking at the hoses at the back of the head to the heater inlet and outlet ports on the firewall. But if not, jfrahm has asked you about bleeding for good reasons, so it would be good to follow thru on that.

John
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Old 11-03-2020, 07:06 PM
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going to research the bleeding process and report back after i do it.

thanks,
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85 Mercedes 300cd sold
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86 944
Old 11-07-2020, 02:02 PM
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Ok, I tried to bleed the coolant via the vent screw, and hot coolant was coming out but it wasn't spraying, or that messy, just kinda flowed out . i let it vent for a good long time but it seemed just coolant was coming out. Then I tried the blow in the reservoir overflow hose and cracking the vent screw method. again, it released coolant but still no heat coming in to the cabin. I think all my hoses are getting hot after about 5 minutes, which seems my thermostat is working, and the car is up to midway on the gauge.

All signs are pointing to bad head unit, right?
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Old 11-15-2020, 05:59 PM
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Thanks for the bleed update. Maybe you already told us, but with the engine hot, were either or both of the hoses to/from the heater core also hot? (Sorry for statement of obvious), one flows hot coolant into the core; it flows out through the other.

John
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82 911SC coupe, 3 seasons near-daily use; 87 924S, project ... see my thread http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/1046846-johnjs-87-924s-rehabilitation.html Past: 6x Alfas; 01 V70 2.4T; 95 Accord CD555; 89 944S2; 89 FJ62 Landcruiser; 82 Celica; 77 CJ5; 74 Beetle; 67 TR4A; 62 Midget; ?Year Lambretta Li 150 (my brother's actually); 76 Fiat 126 (Mum's); ?Year Isetta 300 (Dad's)
Old 11-16-2020, 07:33 AM
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I don't know if there is a failure mode for the head unit for no heat. More likely the heater core is plugged up or there us a big mouse nest in there or something blocking airflow though the heater core.
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1994 968 cabrio - Supercharged
Old 11-16-2020, 09:58 AM
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Why am I not seeing the bowden cable that moves the control valve arm?
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Old 11-18-2020, 10:45 AM
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Late cars use a Vacuum system. The vacuum can pictured closes the heater valve when activated.

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Old 11-18-2020, 11:39 AM
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