'72 rear defroster questions

Am I correct in my understanding that a single-stage rear defroster was standard in '72, but the dual-stage was optional?

I'm looking at all the various things I'll want to deal with while the glass is out for paint, and the rear glass and defroster is an open question.

The car is wired for 2-stage (brown, red/white and red/black). It has a two position switch. The glass now in the car (with a probably non-functional grid) looks like single-stage (9 grid lines, no obvious zones, and looks like there would have been only 2 connector tabs if they weren't already missing).

Wouldn't surprise me much to find the rear glass is not original. But while I don't have a CoA or whatever they call it now, I do have a verbal report of the car's option numbers that was obtained from Porsche by someone in the UK. That list of options does not list 2-stage defrost. Nor does the Tourist delivery order form for '72 list it.

I've seen that the 2-stage may have only been available with full tinted glass, which my car does have (option 568). Did full tinted windows include the 2-stage defrost in '72? Inquiring minds want to know...

Quote:

---

Originally Posted by Arne

Am I correct in my understanding that a single-stage rear defroster was standard in '72, but the dual-stage was optional?

I'm looking at all the various things I'll want to deal with while the glass is out for paint, and the rear glass and defroster is an open question.

The car is wired for 2-stage (brown, red/white and red/black). It has a two position switch. The glass now in the car (with a probably non-functional grid) looks like single-stage (9 grid lines, no obvious zones, and looks like there would have been only 2 connector tabs if they weren't already missing).

Wouldn't surprise me much to find the rear glass is not original. But while I don't have a CoA or whatever they call it now, I do have a verbal report of the car's option numbers that was obtained from Porsche by someone in the UK. That list of options does not list 2-stage defrost. Nor does the Tourist delivery order form for '72 list it.

I've seen that the 2-stage may have only been available with full tinted glass, which my car does have (option 568). Did full tinted windows include the 2-stage defrost in '72? Inquiring minds want to know...

---

Yes, 2 tinted windows all came with 2 stage heater grids after 1969. Clear glass had single stage heating. Look at the logo on the glass. The top line will read "Sekurit or Sekurit 1 if it is clear. Tinted glass will read Sekurit - F.

Here all this time I've been focused whether the defroster grid was single or dual stage, never looked closely at whether that glass was tinted or not. It is clear. All the rest of the glass is tinted with the '-F' suffix. So the rear glass is not original to the car, and I'll want to find a tinted replacement while the glass is out for paint.

Attachment 494418

Quote:

---

Originally Posted by Arne

Here all this time I've been focused whether the defroster grid was single or dual stage, never looked closely at whether that glass was tinted or not. It is clear. All the rest of the glass is tinted with the '-F' suffix. So the rear glass is not original to the car, and I'll want to find a tinted replacement while the glass is out for paint.

Attachment 494418

---

You should be able to find a tinted rear glass locally. I can tell you that tinted back glasses for 911 Coupes are one of the least saleable items on the car. Don't let anybody tell you they are rare and worth a lot of money. I smashed about 100 of them when I closed my business. They are actually fun to destroy! Don't plan on the heater function working, either. If the glass has been cleaned a few times, they will have broken the continuity in the painted on wires. By the way, there is no such thing as an "unscratched" back glass.

Regards

Jim

This is the 1 thing on my car that doesn’t work. Even if i can’t get it to “work” due to glass connections being broken, id like everything else to function. OCD problems.

I did some searching, but is anyone aware of a methodical debugging approach to troubleshooting this?

It's electrical, so the same as any other electric accessory. Trace the power flow and check the grounds. The normal issue is as Jim notes, the painted "wire" traces are easily damaged over time. While I too would prefer to have it work, my main concern is to have tinted glass to match the rest of the glass in the car.