utfan01ss

iTrader: (1)

I'm having a hard time tracking down this no heat issue. I recently installed new injectors and had to replace the intake manifold on my 89 IROC. Before doing this my heat worked fine... now it doesn't. So that tells me its something I did. When I tore it down the vacuum lines fell apart, old and dryrotted.

I noticed it would not blow through the vents, only defrost... as this is the default setting. So I ran a new vacuum line from the intake to the HVAC hard line that enters the firewall and a new line to the heater valve on the passenger side. It blows through the vent in the vent position and the heat blows through the bottom as it should. But its blowing cold air... so it sounds like the door that switches between the heater core and A/C is not working properly. Is this ran on vacuum or cable?

Now for reference... the HVAC controls are ran on vacuum from the vacuum canister correct? It comes from the drivers side canister, through a one way check valve then into the HVAC. And the other line runs to the heater valve on the heater hoses? That long plastic line that runs from the throttle body to the vacuum canister broke so I eliminated it. Capped off the throttle body vacuum port. As I didn't know if I could get a replacement hard line. But my heat should still work as long as its getting constant vacuum from the engine correct?

Driving to work in 14 degree weather sucks with no heat... thankfully I had the car in the garage so it wasn't too bad. Any help would be greatly appreciated. Thanks

l_dis_travlr

After reading your description, I'm still a bit confused, but here's
my based on removal/restoration of my unit.

If you're getting cold air (regardless of where) when the heater
temp control is in the hot position, my first response is that there isn't
hot water flowing through the heater core. Where the air flow is directed,
is controlled by the function lever directing vacuum to 3 (if memory serves
correctly) vacuum servos moving small "doors".

Possible checks, when the controls are set for heat function:
-- are both heater hoses hot to the touch?
If not, the heater control valve is not functioning properly.
-- check for vacuum at the heater control valve.
(Sucking sound when removed...)
If so, the heater control valve is bad.
If not, and vacuum into the control panel is confirmed, then the
problem will be in the control panel. Probably unlikely since the problem
can be correlated to the manifold switch.

Good luck, & keep us posted.

utfan01ss

iTrader: (1)

Thanks,

I think that Heater / water control valve may be my issue. Does vacuum open the valve or close it? I ran a line from the drivers side front on the throttle body, that little vacuum port on the bottom, but wasn't getting any vacuum at all. I may try to run one from the rear of the intake plenum to see if it'll work.

The control panel is in fact getting vacuum, as it switches between vent and heat. But it should send vacuum through the firewall to the water valve shouldn't it? I'll mess with it tonight and see if I can figure it out. Thanks again for the help!

And it doesn't feel like the heater hoses get hot... but I have a 160 thermostat. Even with it the heater should work... so hopefully its just that valve staying shut.

IROCU2

Any progress on the heat? I am experiencing the same issue.

utfan01ss

iTrader: (1)

My heater control valve wasn't working properly. I also noticed I had a small hole in the heater hose which runs into the metal pipe along the frame... so I eliminated that pipe and heater control valve. Ran new 5/8 hose from the core to intake manifold and 3/4 from the core to the radiator.

Blows nice and hot, not an issue since. Once the weather gets warm again I'm going to install that metal pipe, run the hoses as they were factory, and install a new heater control valve so it won't affect my A/C. Try that and see if it helps... I spent less than twenty bucks on heater hoses from O'Reillys. They come in a bag with 6 feet of hose. Perfect amount to run them...

JohnnyT/A

Utfan01ss I have a 160 thermo as well and could of swore that was the reason I wasn't getting any heat??
You have one too and is it very hot?
I've read on here that if you have a thermo under 195 then you will never get really warm air. My issue is driving me nuts. I'm no mechanic but can do small fixes. Any chance you can post some pics of what you did to make this work?