Heater trouble- what's wrong?

[kevin-design]

I hadn't had the opportunity to try out the heat in my '92 vette since I bought it until the recent cold. After trying it out, I realized now that it doesn't work- just blows cold air. Seems to me that since the fan is working, and coolant should always be circulating through the heater core, the only way this could not be working is if the core was bypassed or the engine had no coolant. The engine runs normally, coolant level is normal, and it doesn't overheat when I'm driving it. I checked the routing of the rubber hoses and it seems like they are where they should be running into the firewall on the passenger side. I assume these are the in/out ports for the heater core.
While running the car, I went over and squeezed these hoses and they don't seem to be under pressure or have anything flowing through them as I'd expect. Maybe this is a problem with my thermostadt?
If I do need to replace the heater core, will the method described here: http://forums.corvetteforum.com/zerothread?id=531792
work for my '92?
And since I have your attention- the other weird thing that's happening lately is that the starter motor seems to be sticking on the flywheel teeth. It just won't turn at all, then if I put the car in gear and rock it a little, it starts up.
Any ideas appreacited!
Thanks!
-Kevin

 

[Redmanf1]

On the starter it sounds like you need to shim it. First thing on the heater is to make sure that your coolant is full if it is not it will not circulate through the heater core also check your coolant cap it will not heat or cool properly if it does not pressurize correctly. If those are ok I would replace the thermostat and apply presser through the heater core one of two ways either by air or water. If you have access to air you can cut the presser down to about 20 to 25 pounds take both heater core hoses off and apply presser to one of them you can do the same with water but make sure that you have a container for what exits out of the hearer core so you don’t get it all over you and the car. You should be able to tell if it was restricted. I would then flush with water reapply hoses and add coolant. Make sure that you get the air out of the system and all should be fine.

 

[jmccloud]

Heater

Do you have manual or automatic A/C control (C60 or C68 rpo code under the lid of the storage tray behind the passenger seat)? If manual control, could be the control wire on the back of the heater control is loose or broken. If automatic, could be a bad control head or jambed control door.
Which A/C do you have?

To further diagnose the heater core and flow, are the tubes leading to the firewall hot once the car heats up? If so, you have flow. If not, no flow. Normally there's 15-17psi on that core due to the pressurizing cap on the fill tank, once the car heats up.

 

[kevin-design]

thanks guys! Here's more info:
From what I can tell, there is no flow to the heater core, but like I said, it doesn't appear to be bypassed either. I don't understand why coolant wouldn't be flowing through the system as it appears to be flowing properfly throughout the rest of the engine. The hoses are not hot after running the engine. I have the automatic climate control system in my vette.
Since cool air is blowing out the vents, that would indicate that the control door is functional, right?
I have no evidence of a heater core leak (knock on wood) but will try some of tests that you have suggested later today. Overall I'm still confused to how this is happening- the thermostat controls only the flow to the radiator, right? (flows once the engine warms up..?) The pressurinzing cap on the fill tank- what does that control exactly?
thanks for any help!
-Kevin

 

[brookman]

Your heater core is probably plugged. remove the hoses at the engine and stick a garden hose one one of them. water should flow out the other hose. If it doesn't - put the garden hose on the other side.

 

[stumpy]

Yep, probably plugged. Disconnect the hoses and fill the lines with as much water as you can, then blow it out with air pressure. Repeat until the foul dirty gunk is all gone.

 

[kevin-design]

thx!

Well, I have to admit, I was skeptical of the idea that the core was just plugged, but sure enough, after some flushing of both core and throttle body, heat works fine. It never took much pressure and no solid material that I could see came out, but apparently that was the problem. I guess two lines are pressurized such that if there is even a light blockage of the core, the coolant will just flow through the other route?
Anyway, thanks for the advice guys! Good job!

 

[scarbro2k]

No Heat from heater

Hi ! I had the same problem with no heat. I ran the
ECC diagnostic and everything came out ok. But, no heat.
I felt the hoses going to the heater core. One was hot
and the other was cold. I disconnected both hoses and
used my garden hose to flush the heater core. WoW!
It looked like Georgia MUD!! Refilled and removed air from the
coolant system. Bingo ! HOT/warm air !
I should have done this back in July when I replaced the
water pump and Optispark. That task was a fun job.

Still a Happy 94 Vette owner.