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> Heater Control question
Black914_4
post Jan 19 2012, 07:11 AM
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Would someone mind explaning how the heater controls work please.
I have the '74 914 with the 2.0.
I need to know what levers does what.
ie. - middle lever moved to left does ..., to the right does.., bottom lever moved to left or right does...
Thanks
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flipb
post Jan 19 2012, 08:19 AM
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This is from memory, so others please correct me if I'm wrong:
  • Red Lever on floor: Opens heat flaps to bring heat into the cabin. When pulled back fully, engages auxilliary blower fan for heat - usually not necessary as engine impeller RPM is sufficient to heat the cabin really well
  • Bottom lever of HVAC: Controls where the heat enters the cabin. Far left = footwell, far right = windscreen defrost, middle = dash vents in later cars
  • Middle lever in HVAC: Controls where fresh/cold/vent air enters the cabin - same positions as bottom lever, but for fresh air
  • Top lever in HVAC: Controls the flow of fresh/vent air. Left = off, Right = full

Oh, and (IMG:style_emoticons/default/welcome.png)
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Dave_Darling
post Jan 19 2012, 12:42 PM
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And far right on the top lever should turn on the fresh air blower. If the fan motor still works, that is.

--DD
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flipb
post Jan 19 2012, 01:13 PM
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QUOTE(Dave_Darling @ Jan 19 2012, 01:42 PM) *

And far right on the top lever should turn on the fresh air blower. If the fan motor still works, that is.

--DD


I always thought that the top lever was sort of a rheostat for the vent fan. Left=off, middle = varying degrees of on; Right = blowing full blast (which isn't much!)

Am I mistaken?

I vaguely remember testing it with the engine off (ignition turned on) and listening to the sound of the fan at different settings.
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Cevan
post Jan 19 2012, 01:55 PM
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Top lever controls the speed of the fresh air fan. There are 3 speeds. At least in my '75.
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Dave_Darling
post Jan 19 2012, 04:03 PM
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QUOTE(flipb @ Jan 19 2012, 11:13 AM) *
I always thought that the top lever was sort of a rheostat for the vent fan.


Not really a rheostat, no.

At the far left, the fan is off and the flaps from the inlet in the cowl are closed. As you slide the lever to the right, the flaps from the inlet are gradually opened up. I think they're fully open somewhere past halfway. Then you get to the fan on low speed, then the fan on medium speed, then the fan on high speed. Those are done with resistors, so that is sort of kind of like a rheostat. Sort of.

Some or all (?) of the panels have marks for the fan, you'll see "I" and "II" and "III". Those are approximately where the fan comes on at that speed.

--DD
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mrholland2
post Jan 19 2012, 05:00 PM
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How "needed" is the fresh air part? Is it a safety issue? I'm thinking of reworking this whole system a teeny bit. . but maybe not? I live in an area where it could be 80 in the day and 40 at night. Or blizzard, like right now, but I wouldn't drive the 914 in the blizzardy weather.

QUOTE(Dave_Darling @ Jan 19 2012, 02:03 PM) *

QUOTE(flipb @ Jan 19 2012, 11:13 AM) *
I always thought that the top lever was sort of a rheostat for the vent fan.


Not really a rheostat, no.

At the far left, the fan is off and the flaps from the inlet in the cowl are closed. As you slide the lever to the right, the flaps from the inlet are gradually opened up. I think they're fully open somewhere past halfway. Then you get to the fan on low speed, then the fan on medium speed, then the fan on high speed. Those are done with resistors, so that is sort of kind of like a rheostat. Sort of.

Some or all (?) of the panels have marks for the fan, you'll see "I" and "II" and "III". Those are approximately where the fan comes on at that speed.

--DD
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Dave_Darling
post Jan 19 2012, 06:32 PM
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Only you can tell how "needed" it is. I like to have it, but I wouldn't say that it is absolutely critical. After all, you can just pop the roof off or open the windows to get ambient-temperature air.

--DD
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GeorgeRud
post Jan 19 2012, 09:23 PM
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It's nice to be able to use both the fresh and hot air system together when you really want some ventilation in the car on a rainy day. I'd leave the system like it was designed and be sure things are properly adjusted (heater control flaps) and not worn out (heat exchangers).
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Black914_4
post Jan 20 2012, 06:54 AM
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I appriecate the help. That was what I needed to know.
Thank you for the welcome flipb, Glad to be here. (IMG:style_emoticons/default/biggrin.gif)
So far I've been pretty lucky with my car. Bought it 2 weeks ago, non running without much history. All orginal, all matching, all there, still fuel injected. Rebuilt/cleaned distribator, replaced vac and gas hoses. So far just about everything works. Been driving it almost every day! I love my car (IMG:style_emoticons/default/biggrin.gif)

Needs paint job, new weatherstripping, and seats redone, and a few other things fixed up but not a bad investment for only $1,500.

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johannes
post Jan 20 2012, 08:00 AM
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QUOTE(GeorgeRud @ Jan 19 2012, 07:23 PM) *

It's nice to be able to use both the fresh and hot air system together when you really want some ventilation in the car on a rainy day


(IMG:style_emoticons/default/agree.gif)
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partwerks
post Jan 20 2012, 08:05 AM
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You'd think that with the squirrel cage helper fan, they would have plumbed it so that it puts in warm air back into the system, instead of sucking in cold air back in when utilized.

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442nd914s
post Apr 14 2013, 08:25 PM
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Hope you guys don't mind if I piggy back off of this topic, but I have a related question.
What makes the defrost lamp cover to illuminate? My bulb, dash controls, and console switch work fine. Both blowers working and heat is available. However Im not getting any voltage to my indicator with the levers in any position. I've checked underneath the cover plate with the nut and screw connection.
If I could just get some assistance on where check next. Everything else on the car works perfect (knock on wood).

Thanks for your help
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Dave_Darling
post Apr 14 2013, 10:15 PM
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QUOTE(442nd914s @ Apr 14 2013, 07:25 PM) *

What makes the defrost lamp cover to illuminate?


The headlight switch. It is tied to the instrument illumination lights.

--DD
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