Ideas of what I should check? The blower works and blows air and when I switch it to heat it sounds like the vacuum is working. Are the air diverters controlled by vacuum or mechanically?

 

Vacuum. Do you have the Heater control valve hooked up?

 

Is that part of the AIR system? If so, all that stuff is long gone..

 

No its part of your heater system

 

OK, well my car does not have that control valve..? What have the PO's done to this poor car?

 

oh my.....

At a minimum you should at least have a hose going into and out of your heater core

 

Water hoses, yes. With all the time I have spent with my head under the hood I don't recall any "extra" vacuum hoses. I assume this vacuum hose goes thru the firewall?

 

Yes

 

I'll have a look then...

 

It (vacuum line) would've been back by the coil, going into the wire loom and into the cabin to heater controls as shown where my finger is in the pic.

 

OK, found the vacuum hose coming out of the wire loom. They have it routed over to the driver's side and hooked into this three-way connection that goes to the cruise control. Photos below.


What do I need to do to get this working? It's gets mighty cold here in the winter...

 

Just found a diagram of this system in one of my manuals. It shows a water hose going from the TB to the side of this valve. Two hoses exit this valve. One goes to the heater core directly. The other hose leaves this valve and goes to a "T" in the line from the radiator to the other end of the heater core. I noticed part of this hose is metal and that's where this "T" is.


Mine does not have this "T" connection in it. This is a 1986 and I found this '86 has a few things that are specific to 1986 cars. Wondering if this is another case of an oddity in this year or someone has really fubarred this car again?


Also, the diagram does not show a vacuum line to it. I also can't find anything in my Chilton's manual or the factory shop manual that talks about vacuum lines in this system at all. Talks a lot about cables and their adjustments but mentions nothing about vacuum..

 

So what happens when you slide the temp to hot or cold; any change? You might want to check under the dash and see if the cable is connected to the hot/cold bypass.

You checked pretty much everything else. I got a diagram somewhere, lemme look for it.

We'll get ya fixed up before the snow fly's!

 

This is for a 91 IROC, but will give you an idea whats going on in the dash and the operation of the HVAC

 

OK, I think the vacuum portion of the system is working fine. The air diverts between upper vent, floor, defroster and Bi mode just fine. I can even hear the flaps opening and closing. I even hear them moving when I switch it from cold to hot.


I don't think water is circulating through my heater core. It just isn't getting hot enough to heat the air. I just let it get good and warmed up. Hit both my upper and lower radiator hoses with the infrared temp gun and both up around 190. I hit the heater core hoses and they are only 150-160 and I think that's only from the ambient heat of the engine bay while it sits in the garage.


Does that valve with all the hook ups create some kind of water pressure that forces the hot water through the heater core? As it is set up now I have a hose from the TB straight to the core and the other one goes from the radiator up by the overflow straight to the other inlet on the core. And remember my metal portion of hose down there doesn't even have a "T" connection..??

 

Bump guys.. Does it sound like I don't have water flowing through my heater core? Will the way it's hooked up now prevent water flow in/out of the core?

 

I have the same problem as you, except my car is an LS swap car also utilizing a heater diverter valve. I suspect that my heater core is not getting coolant circulating through it.

 

If my brain cells are recalling things correctly, non ac cars were hooked up from 'TB to heater core' and 'Heater core to radiator'. So that should flow fine. 150-160 should still give to warm air. Sounds like the blend door (temperature valve on the diagram) is not moving, even though it sounds like it is. Probably a pain to get to on these cars. I've only dealt with this on cars that didn't have such a difficult dash board.

 

https://www.thirdgen.org/forums/cool...ng-heater.html Here's some good info.

 

According to the info in that other thread it sounds like I am hooked up OK even though my car is an AC car. (Another project for another time) I guess I will have to dig in there and see if the air flap is moving enough.

Water should be flowing, right?

 

So i resolved my problem today, maybe this will help you. For me the problem resides with the vacuum line that tells the diverter valve when to open. I pulled the vac line with the controls set to heat, it had no vacuum. I plugged it into engine vacuum and bingo the heater works again. I think either the module in the car is messed up or that the system has a vacuum leak (some of my blend doors are not functioning too so this could explain it)

 

That's what I suspected in post #2. Divert valve and vacuum lines to head unit.

 

I had this problem last year, it turned out that my blend door arm was broken and in tiny pieces, its worth a check. All that's required is to take off the lower kick panel on passenger side and see if the lever is attached and the door moves when you switch from cold to hot. if its still attached and moving i would suspect a clogged core which you can replace or try to flush with a hose.

 

Got in there this morning and everything is operating as it should. All the blend doors are opening and closing as designed. Warmed up again and the water is definitely NOT flowing. The hoses to and from the core are cool to the touch while you can't hardly touch the upper or lower radiator hoses.


The car has sat for a number of years. I guess I will try to see if the core is clogged. Any other reasons the water would not flow?

 

Disconnect the hose leading to the heater core and see if you can blow compressed air through it. Also check the nipple that the heater hose is connected to at the pump, it may be blocked also.
Its not that hard for water to go in a circle! This got me. You MUST have a blockage at a connection or like you said, the heater core is plugged solid. Especially if it sat.

 

The hard steel line from the radiator to the core was totally blocked by rust and crap. Got it all cleaned out and the heat works like a charm.


Thanks guys!

 

FINALLY!!! I will sleep well tonight!!! Congrats! You owe us all a round of beers!!

 

Good work. I should've suggested that earlier, my LT1 car had a clogged core a few years ago. Glad you got it.