dprantl

The recirc flap should not cause this. In cold weather, most cars will leave the flap open when heating. The heater core should have more than enough capacity to heat up even arctic air. If it works for swedish cars, it should work for german ones too. Heater core dimensions are very similar.

Dan
'91 928GT S/C 475hp/460lb.ft

ROG100

Dan,
We find that the outside air does effect the temp of the center vent air significantly paricularly if its freezing cold. Like wise in the Texas heat when testing AC temps from the center vent. It can make a 20F to 30F difference if the recirc flap is in the failed open position.
Just passing on experiances in our shop.
Roger

jcorenman

The recirc flag is above the passenger's feet, on the underside of the heater box assembly. If you lie on your back on the pass-side floor, looking up, you will see a plastic grill, that's the recirc-intake and the flapper is right behind that. (Personally I use a mirror and a big flashlight )

When the recirc-flapper is "closed" (no recirc) then you can see it through the grill and feel it with a finger or pencil. When the heater-control is set to "off" the recirc flap is open (recirculating) with the engine running. The WSM says that it is closed (not recirculating, i.e. fresh air) in the various heat positions but I think that depends on temperature. In "defrost" it should be open (recirculating).

What is the engine-block temp? It should be around 170-190F once things are warmed up.

If the heater valve is open then the hot-side hose temps on either side of the valve should be the same as the block temp, around 170-190F once things have warmed up. If it is hot on the engine side of the valve and cooler on the heater side, then the valve has failed closed. Unusual, but anything is possible

the flyin' scotsman

The recirc flap defaults closed (fresh air) and WSM shows it only open (recirc) when the controls set to off, defrost or a/c on and there's also temp. settings to consider.

Given the 'low' coolant hose temps I'd be looking at the t.stat as the most probably culprit.

Rod Underwood

I think I may have both. The flap is closed - letting in outside air and the bolck temp does not get above about 170. Double culprit. I'm now trying to find an elegant way to block it open, without the screwdriver so I can drive it to Detroit next week end. I can't see the actuator, I assume it may be accessible from the outside, maybe under the fan, that I just replaced. ;-(

Oh well, any ingenious ways to keep it open would be appreciated.

Thanks all for your help.
Rod

renenkel

Funny....you have no heat and I can't turn mine off....so you're fine in summer and I'm fine in winter....and on the average we're perfectly happy! (Actually, you're probably a bit happier than me, since my AC doesn't work either....getting a new condenser to fix that....)

the flyin' scotsman

There is a way to hold the recirc flap open (normaly done for summer a/c operation) but first I'd ensure that there is not a recirc flap issue first.............set the heat on full and the air poistion on defrost. with the engine running the HVAC system should deflect all hot air to the windshield and the fan should switch to full speed (if the fan is switched to anything other than 0 ). All being good check the recirc flap.........it should be open. That confirmed switch the air position to foot only and the fan should switch to its setting and the recirc flap should close.

John P has a great photo description:

http://members.rennlist.com/pirtle/svc.html

dprantl

Maybe I was not clear in my first post. When the car is fully warmed up, the temp slider is set to full hot and the position slider set to on but not defrost, there should be very hot air coming out of the vents and the recirc flap should be in the position where it allows outside air in. This is how it is supposed to work from the factory. The function of the recirc flap is to recirculate air to improve cold A/C performance in hot environments and to facilitate defrosting speed in cold environments. If you don't have heat, you shouldn't be wasting your time diagnosing the recirc flap as there is something else going on causing your issue.

Dan
'91 928GT S/C 475hp/460lb.ft

j.kenzie@sbcglobal.net

t-stat? low coolant level?

jcorenman

Nope, neither. The problem lies elsewhere.

As Dan said, the recirc-flap will normally be closed (fresh air) except max A/C and defrost. But broken or not, that's not the cause of your no-heat condition.

And 170F block temp is hot, that's right around the t-stat temperature and all the warmer that the engine is going to get idling or under light loads.

You need to pull the air-cleaner box and follow the heat: The block fitting for the heater should be hot, too hot to touch for more than a moment. Same with the short hose to the heater valve (it will feel less hot because it is rubber). Now follow the long hose from the valve towards the heater box, that should also feel quite hot (with the engine running).

Pull the plastic cowl cover and follow that hose to where it disappears into the heater box, should be the same temperature all the way along. Right next to that will be the return line, it should be less hot but still pretty warm.

If all that checks out then the heater core is hot. But your feet are cold, which means that the air is not passing through the heater core, which means the temperature regulator is not working. The 928 uses motor-controlled flaps to mix hot and cold air in order to regulate the cabin temperature. When the heater control is calling for max-heat (i.e. slider all the way right) then all of the air passes through the heater core; when the control wants no heat (slider left) then all of the air bypasses the header core. That is controlled by a motor on the left side of the heater box (accessible-- barely-- by removing the carpet panel on the drivers-side of the console). There are some tests described in the WSM, section 87. Short form, you should see the temp-regulator linkage moving as you move the dial from max-cold to max-hot.

And yes, the recirc actuator is buried under the fan that you just replaced . But don't worry about that for now.

Rod Underwood

You got it right Jim, I found the small box attacted to the mixing box with a lever on the side. I moved the slider and nothing happened, so I moved the lever up and I started getting warm air in the car - immediately!!!

Now to find out why. I suspect the control may be unplugged since I went in behind the radio and found 8 feet of lamp wiring connecting the radio to the speakers. When I have the console out recovering it this week end, I can at least check that.

In any event, I'll not freeze on the way to Detroit Saturday, thanks to you..

I owe you a drink of our choice.

Rod

jcorenman

Great!! Just move the level to max-heat and open the window as necessary

That motor connects to the control-box so there is probably a connector loose at one end or the other. Gotta love the PO wiring jobs!!

WallyP

Go to our web site, click on the photo to open, click on the + by Tips/Links, click on the + by Wally's World, click on The HVAC System.

Print it and read it - it should help.

Rod Underwood

Thanks Wally, I'll print out all of those tips. I didn't know they were there.

Rod

Mrmerlin

usually a problem that all of a sudden starts happening requires the question......

what was the last thing I fixed.

I hope that you find a loose harness connection or a vacuum line that might have gotten pulled out when you refit the console, a visual inspection usually will be enough to find the problem