Firewall hole

[Rey S.]

I am going to attempt to post a photo of a hole in my firewall. Well as it turns out my photo will not up load so I will try my best at a written description. So here goes!This hole is 1.5" in Dia. and is located right of the wiper motor angled towards the right side of the car. Its between the wiper motor and the wiper door actuator and is 7"(+/-) down from the top firewall lip. There is another sizable hole next to it that has part of the HVAC harness passing through it. Any ideas as to what this hole accesses. I checked all my grommets and nothing seems big enough to fit said hole.Thanks for any and all help on this matter.

[Thad L.]

Re: Firewall hole

Yea it sounds like the hvac hole.

[Warren F.]

Re: Firewall hole

Rey,
That area you describe has a smaller hole that has a single very flexible vacuum line running through it only. The hole is not as large as you describe, nor is there another hole near it. This is of course on a 1971 big block, non a/c optioned Corvette.

[Alan S.]

Re: Firewall hole

Hi Rey,I too thought of the smaller hole for the vacuum supply to the heater/defroster controller in the shifter console that Warren mentions.Is/was you car an a/c car? If so look on the AIM at the a/c option section C60, Sheet E3. You'll see that the hole at the location you describe has a larger grommet in it than the non a/c car has. Also, there's a note for that grommet that leads to sheet UPC 0, Sheet A-10, which indicates the hole for the NON a/c car is .68" +- .02". So, the hole you're seeing seems to be for the larger a/c sized grommet. But, I can't find where the AIM indicates the size of the larger hole!More information, but no answer, just what you need?!?
Regards,
Alan

Here's that area of the firewall on my non a/c car. You can see it has just the one small hole for the vacuum supply to the heater/defroster control.

[Edward J.]

Re: Firewall hole

I am going to attempt to post a photo of a hole in my firewall. Well as it turns out my photo will not up load so I will try my best at a written description. So here goes!This hole is 1.5" in Dia. and is located right of the wiper motor angled towards the right side of the car. Its between the wiper motor and the wiper door actuator and is 7"(+/-) down from the top firewall lip. There is another sizable hole next to it that has part of the HVAC harness passing through it. Any ideas as to what this hole accesses. I checked all my grommets and nothing seems big enough to fit said hole.Thanks for any and all help on this matter.

Ray, there is a rubber grommet next to the wiper door size is 1.62 and as it looks the vacuum hoses (2 hoses) for C60 go through, and next to that is another .62 is another grommet for a wire harness thinking the A/C harness. My 72 is a C60 car let me know I can look at my car, but was a very cold day in new England today.

[Rey S.]

Re: Firewall hole

Hi Alan Looking at the photo you include The hole in question is if you look at the "V" notch right of the wiper motor area there is a hole (+/- 1.65" in Dia.) on the left side of that notch and this is the hole in question. My car has another hole (+/- 1/8") in the right side of the notch with a single hole grommet that has some AC control wires coming through it. On your car I don't see (am I missing something?) this right hand grommet hole. Mean while I will check the AIM pages you mention. Did you receive the progress pictures of my car I sent to you a while back. If all goes well I should have the engine in by the end of April.

[Alan S.]

Re: Firewall hole

Hi Rey,
I believe what you're describing is what Edward describes being on his 72 a/c car.
2 holes, 1 small (on the left side of that V), and 1 large (on the right side of that V).
Do look at C60, E3.
Regards,
Alan

[Rey S.]

Re: Firewall hole

Hi Edward, I will dig out my old harnesses and check for vacuum hoses. What do these hose supply?

[Monte M.]

Re: Firewall hole

On my 72 big block A/C car there is a hole with two vacuum hoses going through it. It is on the surface 90* from where the A/C harness goes through the firewall. One of the vacuum hoses comes out the firewall through the grommet you are talking about and then goes into the wiper compartment through the small grommet right next to the wiper door actuator. Once inside the wiper compartment it terminates with an open end.
The other one comes out the grommet and hooks into the vacuum line right under the passengers side hood bumper on the latch. It is a plastic "T" on the drivers side of the "T" the rubber hose is about 6" long and then goes on the 3/8" steel line coming from the drivers side. The 3/8" line goes right under the wiper door actuator along with a smaller steel line.
The thher side of the "T" looks like it goes to the wiper door vacuum switch it self tucked away on the fender well.

I will look it up in the AIM to see exactly what it does if you like.
Monte

[Edward J.]

Re: Firewall hole

Ray as it looks two hoses from outside the car one goes to the vacuum switch under the wiper door color?? and the other starts at the cowl intake door that buried under the wiper cowl next to the fender its a green striped hose, Inside the car the hoses- one of a tee fittings has a yellow hose that goes to the recirc door the other, turns green and goes to the green which feeds the outside cowl inlet door actuator.

[Rey S.]

Re: Firewall hole

Monte nice to hear from you, I will do some more research myself as I too have an AIM. In the mean time you have rattled my gray matter enough to steer my in the right direction. would it be possible to post a picture of the area so I may see just how the hoses are routed? Thanks

[Rey S.]

Re: Firewall hole

To Alan Struck and any other members that wish to chime in on what I question. On Mar 24, 2014 I posted a response to Mr. Struck about a grommet hole in the firewall of my 1972. Well I have finally found a grommet in my old wiring harness that fits this 1-5/8' hole. What I am questioning is that there are Nine (9) wires routed through this grommet. They are as follows a small Black, small tan, small dark green, small lite green, small yellow, small dark brown, these all look to be 18-20g. Also in this harness collection are orange, pink, and a yellow wires, these three appear to be 16-18g wire. All these wire were wrapped together in the one harness and passing through the 1-5/8" grommet. I have checked all my wiring diagrams to no avail. The only thing anywhere close is the Lectric Limited diagram but it only shows 5 wires routed through the firewall in said area. The AIM is not helping at all (that I can find) on this particular subject. Is there any member out there that can clear some of this fog. This could possibly turn into a lengthy conversation so if anyone would rather talk than type E/M me you phone number and I will call you at your convenience. My contact info is in my profile or through NCRS private messages.Thanks for any help and info. Rey

[Alan S.]

Re: Firewall hole

Hi Rey,
All my reference materials are applicable to 71 cars so I don't know quite what you're seeing in your 72 information.
I just did pretty much what you did....I first saw the harness as a single unit passing through the grommet in UPC C60, E3. I then went to the Air Conditioning Wiring Diagram (UPC C60, E6) and see the 6 individual wires (in 71) that are in the harness at that point. They are: 16 y, 16 lg, 14 lbl, 18 dbl, 16 lbl, 18 or. Very different than yours.
Is it possible that some other wires pass through this grommet too, but aren't shown on the a/c pages since they're not part of the a/c system? For instance maybe alarm wires?
I'd gladly speak to you about this but can't until Sunday. I'm leaving early tomorrow morning to attend an all day Tech session a couple hours drive from my home.
If you pm me a number and time, we could speak on Sunday.
I do hope though that someone can offer you some help before then.
I understand how frustrating these things can be.
Regards,
Alan