Slightly Different Heater Control Problem

[Dave DND]

I have a 1996 GMC Safari with a few Heater Vent Control issues.

Please excuse my descriptions, as here in the UK we use different words to describe things, and I am struggling with some of the terminolgy that you guys are using - Words like Panel Blend are leaving me more confused than my fault.

Anyhow, here goes . . . . .

Initially my truck was on the Defrost screen and freeze your feet setting, and after reading some excellent guides on here, I have replaced the broken rigid vacuum pipe that comes from the engine, and also replaced the rubber pipe down to the Vacuum sphere under the bonnet (Hood?).

I now have Vent controls in a few more settings except the ones that point directly at you. The top window setting comes on and off as it should, the passenger feet come on when it should, and the little actuator by the passenger door operates as it should (now that I have fixed that one too)

But from here, I am now stuck.

On the passenger side, I cannot get anything out of the dash vents that are either side of the airbag.
On the drivers side, the one pointing at the mirror is ok, but I have nothing either side of the instrument cluster, nor the one located underneath the steering column.

Any thoughts please?

[Leeann_93]

Is the diverter thingy hooked up under the doghouse cover (cupholder bit)?

[Dave DND]

Hi Leeann_93 and many thanks for taking the time to reply

I have the Doghouse cover / cupholder bit removed, and also I have the front of the dash panel / Radio and Heater Control panel removed also. Not entirely sure what you mean by "Diverter Thingy" but if I understand you correctly, that I should be looking for something around the vacinity of the doghouse cover? What am I looking for exactly? Is this an electronic device, or another Vacuum device? Is a "Diverter Thingy" some form of control actuator then, and if so, does it resemble the one I have just repaired at the lower edge by the passenger door?

Thanks for your help - really appreciated

[Leeann_93]

The black plastic plenum that connects the right side hoses to the left side and also sends some air through the floor to the back seats.

[The Drummer]

This may sound very silly but make sure the vents are opend , just in case .

[paulo57509]

The black plastic plenum that connects the right side hoses to the left side and also sends some air through the floor to the back seats.

The heater duct bit Leeann is referring to is very similar to the one in the link....see the sixth photo from the top in the link.

http://www.astrosafarivans.com/howtotec ... se9195.htm

Sorry...dead astrosafari.com link.

Edit: You can see the HVAC duct Leeann is reffering to in this video:

https://www.youtube.com/watch?v=yMiT5Td8v6o

[Dave DND]

Thats interesting - I now know what you are on about.

However, that duct that comes down over the front of the Dog House in the video has a duct that goes to the right, into the heater box, and a small duct that goes to a pipe under the drivers side. Mine looks different to this, as I only have the duct to the right into the box and then down over the Dog House. All the ducting from the heater box to the drivers side are in separate large ducts that I would like to try and remove, but cannot work out how.

Where that Dog House duct goes into the heater box, above it is a plastic duct, and if I ram my fingers right up there until I can force them no more, I can feel what seems to be a linkage with a big spring on it, that feels very much like the actuator down by the passenger door. Looks maybe like it has a Pink and Blue pipe going to it?

If I can work out how to remove these plastic tubes, I think that this may be a good place to investigate first.

Any pictures / diagrams / videos of how the ducts come out, or what shape they are would be much appreciated

[Dave DND]

OK - an update, as I have now fixed this.

Here in the UK, there is absolutely zero information and our UK Search engines will show pictures of every heater system available except anything of use - the only fault that comes back time after time is that of the broken vac pipe on the engine. Mine was also broken, but did not cure my problems.

I could see that I had vacuum operation, as the actuator by the passenger door was moving correctly, yet no air would come out of the dash vents at all. With the switch panels removed from the dash, I could see that the yellow pipe went into a joint with a grey pipe. the grey pipe went across the dash to the drivers side footwell and then disappeared under the van. I have a rear heater fitted and where the two heater pipes run by the side of the fuel tank, one of them had some sort of valve fitted to it with a piece of the grey pipe attached to it. The pipe had split here and was causing a loss of vacuum. I replaced the pipe and the air vents came to life. I have no idea what that valve does, and my rear heater does not work - something to investigate another day - but at least I now have A/C and air coming out of the correct dash vents.

Hope this helps someone else with a similar problem.

[WoodButcher]

I have a rear heater fitted and where the two heater pipes run by the side of the fuel tank, one of them had some sort of valve fitted to it with a piece of the grey pipe attached to it. The pipe had split here and was causing a loss of vacuum. I replaced the pipe and the air vents came to life. I have no idea what that valve does, and my rear heater does not work - something to investigate another day - but at least I now have A/C and air coming out of the correct dash vents.

Because of the rear heat I'll bet this bit works the way three way electric switches you would find on the top and bottom of stairs. If A is on B is off and visa versa so if one is broke they both don't function.
Glad you found the cure.