For some reason I'm getting no heat on my 88 vette. the fan works fine but all I'm getting is cold air. I remember reading something in these threads about a door that may not be opening or closing. can anyone give me some trouble shooting tips. I'm sure it's nothing serious. thanks

 

If you feel the blower, and you're getting cold air, I don't believe this is a stuck door issue.

Heater control valve perhaps.

 

Let me add that both the upper and lower heater hoses going to the firewall(heater core) are getting hot so I know the water is circulating and the blower motor is working but I'm getting only cold air. What gives? What would prevent the air from going thru the heater core?

 

I don't think that it is possible for you to have a heater core at 200 degrees and feel no heat -- especially if sitting in one place. Check the valve that controls coolant flow through the core. I know that you reported both in and out hoses heating, but double-check. Also, with the engine warm and heater on, try to manually move the valve to the other extreme from where it is and see if that makes a difference.

 

If you have the electronic controls there is no valve in the coolant lines. There is only an electric door to divert air through the heater core. All air goes through the A/C core all the time, whether the A/C is on or not. I will try to post the diagram from my FSM.

 

When the core is plugged up - coolant flows over the top, but not through it. Can you imagine what would happen if it didn't? First verify that the temp door is working. It's accessible through the Evaporator Box - right side of the Firewall. Remove the Blower Module on the left side of the case and look inside. Have someone operate the controls between 60 and 90 and make sure the door moves. If not, try pushing on it with a screwdriver or other blunt object. If the door is flopping around, it's linkage is held to the motor that moves it with a plastic clip and it's probably broken. Access the motor, linkage and clip from the interior by removing the passenger side hush panel and ECM. If you suspect the motor, disconnect and reconnect the battery. When you turn the system back on, the motor should cycle the door between fully open and closed and you should be able to see, feel or hear it doing that. Takes a couple of seconds to maybe a minute and while this is taking placing, no other HVAC components - including the Blower - will work.

If the door works, the core is usually plugged up. Try removing the hoses and flushing it with a garden hose or compressed air. Go easy on the pressure as system design is for 15 to 20 psi - though I once unplugged one with a 125 psi blast from my compressor withough putting a hole in it.

If the core is plugged up, the radiator and coolant passageways in the block and heads may be too - so make sure you flush everything - not just the core. Drain the block by pulling the oil cooler hose at the filter (and the knock sensor if you really want to get all the crud out). Of course if you can't get the core unplugged, you'll need to replace it.

 

Hi donivan, welcome to the forum .
Pakzr is correct, there is no valve on our later 80's model year vettes.

Here are some pics to help illustrate:

the blower module removed


you are looking down into the box to try to see the mix door




In the above pics, the casing is removed, don't remove your casing.

On the inside of the car is another door link. Here are some pics, but keep in mind te entire dash was removed. You would have to try to see it from "underneath" the angle I show in my pic.





Try to see if one of the 2 plastic links is broken or if the core is plugged up.
If those fail, we can see if your controller has a loose solder conection on 2 of it's resistors.
Let us know what you find.

 

excellent guide.......
I love this place.

 

Thanks everyone for your help. I'm sure I'll find the problem with the tips from the forum.

 

Heater core clogged?

Like it says above, hard to believe that that at 200 degrees you feel nothing.

 

If it's freezing outside and it's cooking hot inside the house, will you feel any heat as you stand outside the closed door.

 

Check your water level before you get to carried away.

 

My previous '89 coupe had the same issue. After verifying that the door would not move, I reheated a couple of solder jonts on the ac programmer board. It is above the gas pedal. You'll have to pull some vacuum lines off to get it out. Make a diagram because not all of the colors match up.