Dreaded HVAC problem returns

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27 Apr 2012 12:24 #9009 by mm928
Time to troubleshoot the vacuum system again for the HVAC. I have checked the engine with the mighty-vac following Wally's advice and the heater valve is new last year (although could have failed of course).

The symptom is warm air all the time, but occasionally the cold will kick on fully and work a few minutes, then go away again. I found a check valve in the wrong place in the engine bay but that did not resolve it.

I have replaced all the internal vacuum manifold solenoids last year, but I will go through those with the mighty-vac as well. But I am thinking it may now be a setting motor or a bad temp sensor circuit or maybe a bad vac line.

Wish me luck! Will let you all know how it goes.

1983 928S - 16v 4.7L L-Jetronic
Dark Grey w/ Blue Leather
85/86 exhaust manifolds
Y-Pipe
SS Hi-perf Cat
S4 springs
Bilstein shocks
Air pump delete
VIN: WP0JB0926DS861180
- - Isn't Life great? - -

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27 Apr 2012 21:23 #9013 by 928mac
Replied by 928mac on topic Dreaded HVAC problem returns

Time to troubleshoot the vacuum system again for the HVAC. I have checked the engine with the mighty-vac following Wally's advice and the heater valve is new last year (although could have failed of course).

The symptom is warm air all the time, but occasionally the cold will kick on fully and work a few minutes, then go away again. I found a check valve in the wrong place in the engine bay but that did not resolve it.

I have replaced all the internal vacuum manifold solenoids last year, but I will go through those with the mighty-vac as well. But I am thinking it may now be a setting motor or a bad temp sensor circuit or maybe a bad vac line.

Wish me luck! Will let you all know how it goes.


Good luck, I haven't gone there yet

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29 Apr 2012 19:59 #9035 by mm928
Replied by mm928 on topic Dreaded HVAC problem returns
Trust me - you don't want to.... :) I think it is something that will just nag until I get a lot of old rubber line and bad flaps etc. replaced,,,unfortunately the ones on the inside are bears to deal with. Even then it may haunt for a while.

To start I may wire the heater valve shut to prevent Hot h2o from entering the tank. It is a quick fix while I take time to troubleshoot. Even then, I may wait until I get the dash out to get the interior done....do it all at once. Until then I will have A/C for the sweltering Va summer....and the trip to NC for SITM on I-81. Will keep you posted.

1983 928S - 16v 4.7L L-Jetronic
Dark Grey w/ Blue Leather
85/86 exhaust manifolds
Y-Pipe
SS Hi-perf Cat
S4 springs
Bilstein shocks
Air pump delete
VIN: WP0JB0926DS861180
- - Isn't Life great? - -

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29 Apr 2012 23:43 #9047 by 928mac
Replied by 928mac on topic Dreaded HVAC problem returns

Trust me - you don't want to.... :) I think it is something that will just nag until I get a lot of old rubber line and bad flaps etc. replaced,,,unfortunately the ones on the inside are bears to deal with. Even then it may haunt for a while.

To start I may wire the heater valve shut to prevent Hot h2o from entering the tank. It is a quick fix while I take time to troubleshoot. Even then, I may wait until I get the dash out to get the interior done....do it all at once. Until then I will have A/C for the sweltering Va summer....and the trip to NC for SITM on I-81. Will keep you posted.


I bought some of that cool orange, blue and red and gray silicon line and is it ever sweet.

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30 Apr 2012 07:49 #9048 by denhamfly
I put a manual valve in my heater line. I block it in the summer and open it in the winter works great. I got tired of not knowing if it was going to work or not! Too hot in Louisiana not to have a/c blowing 100%.

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05 May 2012 19:33 #9090 by mm928
Replied by mm928 on topic Dreaded HVAC problem returns
Hey - great minds think alike! That is exactly what I ended up doing today.

Went to Napa and bought the BK 6601413 (3/4" hose), all metal manual heater valve. It fit in line as a direct swap with the normal heater valve I took out. Just capped the Vac line going to the inside. Didn't not lose too much H20 either just plugged the ends with rags during the work.

Went for a drive and voila! A/C or Fresh Air,,,,either or! Since I have owned it I have never experienced such normalcy in the HVAC. I am ecstatic :D

Taking off the air cleaner itself is probably harder, so it is not a big deal to do the swap. I heard some people put it inline along with the regular valve against the firewall, but that looked really to hard to get to and cutting that hose made me VERY nervous. So it works great as-is and is just an hour job or so now that I have everything.

I am keeping the regular valve to put back for winter. The reason is because it does seem to allow some temperature variation for heat. For Summer, all cool 100% is no big deal, I can switch to a lower fan speed. In Va, when it is really hot, you need 100% cool. And when it is nice, the sunroof and fresh air is plenty.

Total cost - $20.00. Best bang for the buck you can do most likely if you are having all hot issues. it also showed that most of the rest of the system was in pretty good shape since I have get fresh air or Econ and defrost along with A/C whenever needed. I was getting hot all the time, now everything works, (except heat of course) even out of the door vents which were especially hot, and all I did was cut the hot water off.

I tested the old valve a little. It is actually only a year old, the replacement plastic one. But I filled the end with water and it would drip a little, so it was likely leaking even when closed. It would hold a vacuum. But now I can be sure hot water is not getting in....AWESOME.

1983 928S - 16v 4.7L L-Jetronic
Dark Grey w/ Blue Leather
85/86 exhaust manifolds
Y-Pipe
SS Hi-perf Cat
S4 springs
Bilstein shocks
Air pump delete
VIN: WP0JB0926DS861180
- - Isn't Life great? - -

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05 May 2012 19:35 #9091 by mm928
Replied by mm928 on topic Dreaded HVAC problem returns
Hey MAC I like your orange lines. I bought Yellow silicone for everything that was vacuum. Did not get it all yet but I got about 80-85% probably converted.

I think it dresses things up, not to mention makes it easier to see what you are looking at...;)

Fun to make the engines look interesting.

1983 928S - 16v 4.7L L-Jetronic
Dark Grey w/ Blue Leather
85/86 exhaust manifolds
Y-Pipe
SS Hi-perf Cat
S4 springs
Bilstein shocks
Air pump delete
VIN: WP0JB0926DS861180
- - Isn't Life great? - -

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06 May 2012 00:11 #9096 by 928mac
Replied by 928mac on topic Dreaded HVAC problem returns
Glad you are having fun Michael.
I had a lot of fun dressing up my engine.

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09 May 2012 17:31 #9116 by mm928
Replied by mm928 on topic Dreaded HVAC problem returns
What would really be cool is a switch controlled metal valve we could open/close from inside! That would add a funky switch to the inside and negate making the change 2 times per year. Maybe even locate it on the dead switch where the Windows and sunroof switches are.

1983 928S - 16v 4.7L L-Jetronic
Dark Grey w/ Blue Leather
85/86 exhaust manifolds
Y-Pipe
SS Hi-perf Cat
S4 springs
Bilstein shocks
Air pump delete
VIN: WP0JB0926DS861180
- - Isn't Life great? - -

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09 May 2012 21:25 #9117 by pcar928fan
Michael, that would be an excellent idea. Not sure the best way to make it happen, but it would be nice to have that set up so it was easily controlled as it is a common failure point for our cars!

James
78 Silver / Black-white #295
84 Ruby Red / Black AO84
88 Dark Blue / Linen-Black
92 Polar Silver / Dark Blue 92EURO
93 Arrow Blue / Black

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09 May 2012 23:44 #9122 by 928mac
Replied by 928mac on topic Dreaded HVAC problem returns
Something like this

www.thermotion.com/topic/19-automotive-h...r-control-valve.aspx

www.thermotion.com/pdf/Automotive_Heater...Valve_Data_Sheet.pdf

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10 May 2012 09:22 #9126 by mm928
Replied by mm928 on topic Dreaded HVAC problem returns
Now maybe we can get Paul Champagne to look at it since he developed that replacement switch panel already? Hhhhhmmmmmm
Anyone near Paul down there in Texas?

1983 928S - 16v 4.7L L-Jetronic
Dark Grey w/ Blue Leather
85/86 exhaust manifolds
Y-Pipe
SS Hi-perf Cat
S4 springs
Bilstein shocks
Air pump delete
VIN: WP0JB0926DS861180
- - Isn't Life great? - -

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10 May 2012 09:24 #9127 by mm928
Replied by mm928 on topic Dreaded HVAC problem returns
Purists might not like the idea, but I kind of think it would be fun for those us who enjoy a few customizations :)

1983 928S - 16v 4.7L L-Jetronic
Dark Grey w/ Blue Leather
85/86 exhaust manifolds
Y-Pipe
SS Hi-perf Cat
S4 springs
Bilstein shocks
Air pump delete
VIN: WP0JB0926DS861180
- - Isn't Life great? - -

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