1988 CV HAVAC Question

[friskyfrankie]

On the above mentioned car, there are two vacuum lines that come out of the HVAC Check Valve. One goes to the vacuum canister ("coffee can"). Does anyone know EXACTLY where the oner one goes? I would think it would go to the firewall for the HVAC system, inside the car. I can see a broken line, from the line in question but no corresponding broken line near the firewall. Any ideas?

[kishy]

You are correct, it goes through the firewall and if I recall correctly, it joins into a big bundle of vacuum lines that go into a big connector just behind/below/to the left of the HVAC control head. It passes through the firewall in a grommet, which when seated in the driver seat, is vaguely in the location your right thigh is pointed at.

It is possible that it tees off and goes over to do something with the automatic climate control as well, but the basic idea is, that black line is the supply for all of the HVAC controls.

[gadget73]

yep, into the firewall and there is a tee. One side goes to the controls on the dash, the other goes to the thermal blower lockout switch, so any leak there will make the whole thing go stupid.

[friskyfrankie]

yep, into the firewall and there is a tee. One side goes to the controls on the dash, the other goes to the thermal blower lockout switch, so any leak there will make the whole thing go stupid.

Two small vacuum lines are seated vertically at the firewall to the right of the tee (looking from the passenger side under the hood). One probably foes to the TBL and one is probably an input to the HVAC controls in the car. Any idea which is which? Looking for the one that goes into the HVAC Check valve.

[sly]

The two coming out the top of the check valve goes to the vacuum (soup) can on the driver inner fender and the other to the HVAC system. The one that goes to the TBL is a line from the HVAC controls IIRC.

[friskyfrankie]

The two coming out the top of the check valve goes to the vacuum (soup) can on the driver inner fender and the other to the HVAC system. The one that goes to the TBL is a line from the HVAC controls IIRC.

Got it! Just strange that I didn't see where the opposite end, away from the check valve, is broken off. I guess it will take a closer inspection as I know a larger vacuum hose was slipped over the factory hose. The broken line has the replacement hose with a partial OEM stuck to it but I did not see a corresponding broken OEM on or near the firewall. If I do see it and it is not broken off right at the firewall, it will be an easy job to repair. I am just curious where the other end is on the car?

[sly]

Both lines should run driver side... ish... of the check valve. One to the passthrough in the firewall (not very far away, but may be under the wiper motor location and not visible from the driver side at some angles) which should be more towards the middle of the firewall, along with the vacuum line to the parking brake release, and the other completely across to the soup can. This line goes under the wiper motor and over the brake booster before making the bend to the soup can.

Hope that helps.
Also, the TBL vacuum line is the floor vent actuator line.

[friskyfrankie]

Found the broken line today after an EXTREMELY frustrating exercise. Every time you try to touch the OEM line, it breaks. It is really a "two handed" job but NO way you are going to get two hands in there. Was able to hold the broken line with a parts picker and slide a slightly oversized vac line over it about 2-3 inches. Same result - mostly air just coming through the defroster vents so still appears to have a vac leak. Not sure if it is coming from the new line being too big (seems tight, however) or broken under the dash somewhere or at the firewall. Would love to know where it comes out, under the dash and then just re plumb a completely new line since the OEM lines suck donkey Kong! I am sure there is a main distribution port, under the dash and then vacuum is distributed to whatever selection is chosen.

[sly]

Yeah... I imagine that the original lines are trashed at this point and you're probably best replacing the hard lines. PITA to do that though. BTDT.

[friskyfrankie]

What is BTDT?

[gadget73]

Been There, Done That

I've found the lines in the dash are usually still OK but the ones under the hood, forget it. None of my original plastic lines are still there. it got to the point where there were more patches than original line so I just ripped them out and ran new in rubber hose.

[friskyfrankie]

Thanks for the explanation - sorry for my denseness. Would be nice to know where the line that is just under the wiper motor goes to under the dash so I could bypass it with all new line. The other end goes to the AC Check valve. There is one line going to the "soup can" and the other goes through the firewall to under the dash but where does it end up under the dash. Now that is the question....

[sly]

It goes directly to the HVAC controls. It's the black hose in that multicolor pack of hoses (vacuum source).

[friskyfrankie]

It goes directly to the HVAC controls. It's the black hose in that multicolor pack of hoses (vacuum source).

One could probably access it from under the dash without pulling the HVAC Control unit? Then find a way to get the replacement line to the AC Check Valve.

[sly]

Yup. access the HVAC controls from the passenger side is a bit easier than from the driver side, but you only need that if you're going all the way. Probably won't need to since you can couple the line where it's inside the firewall from the driver side. You will need to pull the controls to verify that the vacuum lines are still attached to the controls though. There's a couple of speed nuts (those press on metal disks) that hold the vacuum harness to the controls.