Factory heated windshield

[RatBox]

In a 74 (1st available sometime between 1974MY - 1977MY) - 88 911 (not available after 1988...some private option lists say later. But PET does not list it available past 1988MY).

Apparently , it was option number M577 at some point (heated & tinted).

Is there an on - off switch ? If so , where is the factory location , and what type of switch ?

And if anyone knows what year this option was 1st available , please do tell.


*SORRY , put this in wrong section. I will try the normal tech. section later , if it doesn't get an answer here.

[spuggy]

Originally Posted by RatBox

In a 74 (1st available sometime between 1974MY - 1977MY) - 88 911 (not available after 1988...some private option lists say later. But PET does not list it available past 1988MY).

Apparently , it was option number M577 at some point (heated & tinted).

Is there an on - off switch ? If so , where is the factory location , and what type of switch ?

And if anyone knows what year this option was 1st available , please do tell.

I was seriously considering fitting this option after the fact, when I replace my 250,000+ mile original. I'm told the on/off is the rear defrost knob; on cars with a heated front screen, you apparently twist it for heat on the front.

[RatBox]

Thx spuggy ,

If anyone ever finds any info. regarding year first available .....please let me know.


From some research , I believe it's going to be 1977MY or 1978MY. But i'm not 100% certain , it could have been earlier.

[pht9]

it was definately available for 76MY, my RHD UK supplied 3.0 turbo has one

[RatBox]

Thx much for that info. pht9,

Do you have a report on your car to know if M577 is the correct option number ?

And is yours Tinted all one tint . Tinted with bolder tint also (top darker) , or clear with bolder tint ?


And would it be possible to snap a photo of the markings in the corner ? I would appreciate it.


Best Regards

RB

[GWhite]

Here are the markings from a 1979 Turbo screen, does 'therglas' ferer to the heated screen.

Guy

[RatBox]

Thank you Guy


Yes , Therglas is the registered name of the system. And those are the exact markings I have seen before. I believe Kinon / Kinonglas is the glass manufacturer using the Therglas patented technology.

I have not been able to find it referanced. But DOT 31 , is either registered to this glass co. itself. Or a parent co. that owned it. I have a list of DOT number / to companies up to 700. But it starts at 15 ...goes to 27. Then skips 28-31 , and starts again at 32 ...all the way to 700. DOT number system starts in 1969 by the way.


For referance, I found out this heated , tinted windshield is combined with tinted side glass & tinted 2-stage rear window under option M443. Starting in 1974 model year as far as I know (this is the first year I can find it listed so far). At some much later point (mid to late 80's ?) it must been have changed to M577. This technology was developed decades earlier , but this seems to be the first Porsche use.




pht9 , if you read this . And your 1975 has the exact same markings ...please post. Or let me know whats differant if anything , if you would.

[pht9]

gents, I enclose a picture of the label on my screen

it is green tint with green top tint

[70SC]

Here's mine out of my 70SC . I think it came from a Euro 81 SC ?

[budge96]

I don't recall Porsche windsheilds past or present having heat elements if this is what you're
suggesting ,rear glass yes front screens ,...uhmmmm no.

[spuggy]

PET shows 911-541-101-04 "windshield, tinted, heated" available for the 1974 MY (as well as "901-541-101-24 "windshield" and 901-541-101-34 "windshield, tinted").

Part number changed in 1978, 911-541-011-21 is "windshield, tinted, heated", and there is also 930-541-011-02 "windshield, tinted upper part: dark green, heated".

1973 lists only 901-541-101-21 "windshield" and 901-541-101-31 "windshield, green"

1989 lists 6 different variants of the windshield, tinted/tinted upper part and clear - for cars "with trim frame MOD.89" and cars without.

So 1974-1988 seems to be the years it was a stock option. Last time I got a quote for heated, top tint, 911 windscreen from a national auto glass franchise, it was $1000 as opposed to $250 (from memory) and special-order.

[RatBox]

Correct spuggy .

I thought I went over this in one of my previous posts :

"Starting in 1974 model year as far as I know (this is the first year I can find it listed so far).".

I'm the type that does not make a definative statement , until I know for certain.

I found it listed (m443) , in an august 1974 printed factory options list (for 1974MY obviously).



*I should add for further clarification. M443 includes tinted side glass & heated , tinted rear window.

[drb930]

Can anyone help identify this heated windshield that I want to sell, and what they are worth?

[drb930]

Originally Posted by spuggy

PET shows 911-541-101-04 "windshield, tinted, heated" available for the 1974 MY (as well as "901-541-101-24 "windshield" and 901-541-101-34 "windshield, tinted").

Part number changed in 1978, 911-541-011-21 is "windshield, tinted, heated", and there is also 930-541-011-02 "windshield, tinted upper part: dark green, heated".

1973 lists only 901-541-101-21 "windshield" and 901-541-101-31 "windshield, green"

1989 lists 6 different variants of the windshield, tinted/tinted upper part and clear - for cars "with trim frame MOD.89" and cars without.

So 1974-1988 seems to be the years it was a stock option. Last time I got a quote for heated, top tint, 911 windscreen from a national auto glass franchise, it was $1000 as opposed to $250 (from memory) and special-order.

All these part numbers according to Porsche are now NLA...