HOW TO DO AN ADVANCED SEARCH.

Mon Jul 08, 2013 3:56 pm by Admin


For the benefit of 944Hybrids users there are two search functions available for you to use.
The purpose of this sticky is to explain the "Advanced Search" function because it is much more powerful and is the best choice when researching information.

When you log on to the site a list of options is shown in a line at the top of the page. One option is labelled "Search", use this option (NOT the search box lower down on the right).

After you click on the upper search option, a drop down box appears. At the bottom of this box is a radio button marked "Advanced …

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Heat stuck on high

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Heat stuck on high Empty Heat stuck on high

Post  acorad on Fri Jul 19, 2019 12:17 pm

Hi all, I've been driving my car daily this summer, and it's been great!

Except today...

I turned the temp control knob on my dash about halfway this AM, and the heat came on about halfway just like it should.

A couple minutes later I turned it off, but the heat did not turn off.

I then turned the heat to max, and then tried to turn it off, but the heat stayed on at max. Doh! 🔥🔥🔥!!!

The fuse seems fine, and I checked the infamous fragile plastic clips under the dash, and they are fine (I had replaced them a couple years ago).

I checked the operation of the control arms that the clips are attached to, by starting the engine and turning the heat control knob, and they seem to function just fine.

So now I'm just scratching my head, in a puddle of sweat.  Very Happy

fwiw, I have the standard plastic H-valve - Autozone 74781/Everco 5930. (Although there is no vacuum line to it, and its vacuum port is plugged, so I'm not really sure what the heck it's doing. [edit] I guess that valve is always open, and there is another valve somewhere else? [edit] heat must be controlled by the knob on the dash.)

Any suggestions?

Andy


Last edited by acorad on Tue Jul 23, 2019 5:42 pm; edited 1 time in total
acorad
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Heat stuck on high Empty H Valve Heater control

Post  Porsche951toLS3 on Sat Jul 20, 2019 2:11 am

I have the same H Valve. If you pull the vacuum line off it, it should return to bypass mode since the vacuum line to it has suction when routing the hot water to your heater core. Likewise, you should be able to visibly see the lever moving when you change the heat temp setting from off to high. If not, then you have a problem with your vacuum. My 1986 Porsche 944 Turbo has a vacuum line from the engine to the firewall and then a 2nd line from the firewall to the H-valve. You can see a diagram here to make sure you have the lines correctly orientated. [You must be registered and logged in to see this link.]

You should have the vacuum from the engine going to the top connection at the firewall and the bottom going to your H-Valve.

Hope this helps.
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Heat stuck on high Empty Re: Heat stuck on high

Post  acorad on Mon Jul 22, 2019 11:26 am

Thanks Porsche951toLS3. I think my setup has the under-the-hood H valve always open, and the under-the-dash valve is controlled by the temp knob on the dash.

The under-the-dash valve does look to working when I turn the temp knob on the dash. And when I drove the car yesterday I was able to control the temp with the temp knob on the dash. iow, the whole system seems to be working now as it should.

I really have no idea why it didn't work the other day, I hope it continues to work.

Andy
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Heat stuck on high Empty Re: Heat stuck on high

Post  Rich L. on Tue Jul 23, 2019 5:03 pm

I have a plastic h-valve with a vacuum line to the heater control. If this vacuum line pops off, which it does sometimes, hot water circulates through the heater core in the dash if the hvac asks for it or not. YMMV...

Rich
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Heat stuck on high Empty Re: Heat stuck on high

Post  acorad on Tue Jul 23, 2019 5:22 pm

Rich L. wrote:I have a plastic h-valve with a vacuum line to the heater control. If this vacuum line pops off, which it does sometimes, hot water circulates through the heater core in the dash if the hvac asks for it or not. YMMV...

Rich

So are you saying that if your vacuum line pops off, the HVAC blows full heat into the cabin?

Andy
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Heat stuck on high Empty Re: Heat stuck on high

Post  acorad on Tue Jul 23, 2019 5:41 pm

Here's what I have. Except for the event last week, it's been working great for years.

(Right click and then click "View Image" if you want to see the whole image)

[You must be registered and logged in to see this link.]
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Heat stuck on high Empty Re: Heat stuck on high

Post  Rich L. on Tue Jul 23, 2019 8:11 pm

In my car, not sure if yours will be the same, the HVAC temperature control uses a vacuum signal to the h-valve to allow coolant to circulate through the heater core or not. If that vacuum line pops off, the h-valve's default position is to allow that coolant circulation.

The fan and air direction portions of the HVAC are separate. As is the A/C if you've got it. But if coolant is circulating through the heater core, any air moved by the HVAC will be heated. It may and up being cooled as well if you have the A/C going. Or you might have the fan off and would even notice if coolant is circulating.
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Heat stuck on high Empty Re: Heat stuck on high

Post  acorad on Wed Jul 24, 2019 12:30 pm

Thanks Rich. When the A/C is off, and the dashboard temp control knob is turned down to "Cold," the air I get through the HVAC does not seem any warmer than the ambient air temp, but I guess I can attach the vacuum hose to the Hvalve and see if there's any difference.

Andy
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