Heater blower on a 75 911s

[privatepang]

So i've done the search and most of the issues I've come across are for the later 911's. Mines a 75 with no AC and I recently replaced the blower motor as my last one was shot.

So at the moment when i turn the key on without ignition , the blower starts. If i push the 2 red levers between my seats down, blower still runs. So i've read on other threads that its a yellow cable that might be the issue and I have to remove the seats to get at it.

I'll be giving that a go soon. My other question now is that I'm still not getting warm air in the cabin? played around with the heater controls and I can get cool air come in through the vents at the windscreen but not warm air even with the 2 red levers pulled up.. I put my hand near the blower and there's deiftnley warm air there so I'm thinking either:

a) Heat exchanger is broken
b) read somewhere that if the lever is down, warm air vents to through the exhaust? So cable on the lever might be stretched ? Is this cable just a single black cable? As i can see that going under my carpet from the hand brake assembly going towards the rear.

Sorry for the long thread. Just not sure whether I'm on the right track.

[86 911 Targa]

Originally Posted by privatepang

So i've done the search and most of the issues I've come across are for the later 911's. Mines a 75 with no AC and I recently replaced the blower motor as my last one was shot.

So at the moment when i turn the key on without ignition , the blower starts. If i push the 2 red levers between my seats down, blower still runs. So i've read on other threads that its a yellow cable that might be the issue and I have to remove the seats to get at it.

I'll be giving that a go soon. My other question now is that I'm still not getting warm air in the cabin? played around with the heater controls and I can get cool air come in through the vents at the windscreen but not warm air even with the 2 red levers pulled up.. I put my hand near the blower and there's deiftnley warm air there so I'm thinking either:

a) Heat exchanger is broken
b) read somewhere that if the lever is down, warm air vents to through the exhaust? So cable on the lever might be stretched ? Is this cable just a single black cable? As i can see that going under my carpet from the hand brake assembly going towards the rear.

Sorry for the long thread. Just not sure whether I'm on the right track.

I'm not familiar with your model year, but it might look like this:

[privatepang]

So that photo is the underside of the levers?

[86 911 Targa]

Originally Posted by privatepang

So that photo is the underside of the levers?

It's the cables that are connected to the levers.

[enzo1]

Pelican Technical Article: Heater System Repair - 911 (1965-89) - 930 Turbo (1975-89)

[Walter_Middie]

I'm not familiar with your model year, but it might look like this:

Yes, yours looks just like the picture provided. The vents shown are under the car, just in front of the rear tires. Make sure they are closed with the levers between the seats up, and open with the levers down.

So at the moment when i turn the key on without ignition , the blower starts.

Your blower on the 1975 is on all the time. The levers don't shut it off. The blower comes on when the key is turned on and it stays on.

With the levers down, the heat escapes under the car through the open vents shown in the picture. When the levers are up. the vents are closed and the heat goes into the passenger compartment. You can direct the heat from the heat exchangers with the dash board controls. The dash controls also direct the cold air from the front. You have to mix and match cold and warm air to get what you want.

[privatepang]

Thanks all.

Looks liek i'll be backing the car up to see if the vents are working!

[wwest]

Left and right operate independently, separate push/pull cables and flow/vent valves. With the handles down the valve is open to atmosphere and simultanously BLOCKED against cabin flow. As you raise the handle the BLOCKING opens to cabin flow as the atmospheric vent closes.

Even by yesterday's standards the blower is HORRIBLY inefficient. You can improve it dramatically with an easy modification. Use a larger squirrel cage blower wheel that minimizes the opening between the inlet and the outer edge of the blower wheel or add a metal circular band to block the forced airflow from flowing back into the inlet side of the blower wheel.

The idea behind the factory design was to allow easy flow around the blower wheel for forced airflow from the engine fan. But the real problem is moreso the lack of system airflow with the engine at idle or nearby, or in some sense, COLD weather, even simply cruising along in a high gear...low engine RPM.

Later models, circa '88, added two BOOST airflow blowers, one each in the left and right kick panels, to assist in HEAT airflow and as an aid, a long needed AID, in defogging the interior surface of the windshield.

[Walter_Middie]

Use a larger squirrel cage blower wheel

WWest - do you have a source for a blower cage wheel that will work? I'd love to make this modification. Heat and defrost have always been an issue for me.

[wwest]

Originally Posted by Walter_Middie

WWest - do you have a source for a blower cage wheel that will work? I'd love to make this modification. Heat and defrost have always been an issue for me.

I actually used the metal ring/band approach on my '78 and it's over in McCall ID at the moment.