Defrost lever questions

[f3nr15]

Hi all;

Just wanted to clarify something about the heater controls -

In the '74-75 cars, there was only a single red defrost lever between the front seats. Did this single lever open both heater flapper boxes?

In the '75-76 cars, there were 2 defrost levers - I assume that each lever opened its respective heater flaper box only? Does the engine heater blower become activated on raising either lever, or do both levers have to be raised for the blower to start?

Thanks!

[ossiblue]

Here's how it worked on my 75S.

The blower in the engine compartment is always on regardless of the heater--it functions as part of the engine cooling system. As far as the red levers, you are correct in that each lever opens the heater valve separately. By the way, though it says "Defrost" on the lever handle, it really means heat to the cabin. It's up to you to move the dash lever to the defrost position. You probably knew that so please don't be offended by my comment.

[f3nr15]

Thanks L.J!

So the engine heater blower is ALWAYS on when the engine is running? For some reason I was under the impression there was a microswitch associated with the red levers for the blower.

[BZ911SC]

Originally Posted by f3nr15

Thanks L.J!

So the engine heater blower is ALWAYS on when the engine is running? For some reason I was under the impression there was a microswitch associated with the red levers for the blower.

I had the same impression. I can't remember where I read it but I did just recently. It might have been in my Bentley or Wayne's book.

[Mysterytrain]

Yep, I just checked the factory schematics the 74/75's had no switch, the blower was always on. Learn something new here everyday.
From 76 on they used a switch to control the relay that fed power to the blower motor. That relay did appear on the 74/75 cars too.
As for answers to your questions. The single lever opened both flappers boxes. The double lever arrangement allowed the flapper boxes to be opened individually but either lever would power up the rear blower.

[76912E]

To throw a slight twist to the heater lever question, the single red lever, between the seats of my '76 912E, opens both flapper valves AND turns on/off the blower motor in the engine compartment. If you want a switched lever look for one from a 912E.

Fran

912E, #224

[f3nr15]

Okay, thanks guys!

When did the engine heater blower first make an appearance? 73? 74? 75?

What was used in earlier cars, before the blower? Nothing? (i.e. the red lever simply opened the flappers, with no blower to speak of?)

[Milo2361]

my 80's blower kicks on when i turn on one or both levers.... works great


also - - no intention to hijack the thread but waht the heck are the other 2 levers on the dash for? i know the bottom one is defrost for windows, but what are the top 2???? i hear something kick on when i move em but nothing comes out?

[f3nr15]

IIRC, the topmost lever controls the amount of fresh air coming in to the cabin, the same way the defrost levers control the amount of heated air. It also activates the trunk blower if pushed far enough.

The middle lever controls the direction of the fresh air (towards windscreen or towards feet).

The lower lever controls the direction of heated air (towards windscreen or towards feet).

[javadog]

Originally Posted by f3nr15

Okay, thanks guys!

When did the engine heater blower first make an appearance? 73? 74? 75?

What was used in earlier cars, before the blower? Nothing? (i.e. the red lever simply opened the flappers, with no blower to speak of?)

'75. Prior to that, there was no auxiliary blower. The source of heated air has always been ducting that took air from the engine's cooling fan and directed it through the sheet metal wrapped around the header pipes, so there has always been forced air. The auxiliary blower was really used to boost the heater output at low engine revs.

JR