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All positions work as far as the fan goes feet, feet face, defrost A/C works replaced the blend door last night still the same result. Help with my step I'm thanking the controller rebuild? Thanks in advance for your time.
From: Clifton Park, NY ............Clearwater, FL ... 85 Original Owner
Originally Posted by temcgregor
All positions work as far as the fan goes feet, feet face, defrost A/C works replaced the blend door last night still the same result. Help with my step I'm thanking the controller rebuild? Thanks in advance for your time.
There is no hot air blowing from the vents into the cabin when selected on the HVAC control panel. Just cold air blend door moves and all vents blow air when selected.
Last edited by temcgregor; Nov 26, 2018 at 11:58 AM.
We need to know more about the Corvette that we are talking about. You need to provide more information so people can help you determine why you have no heat. Some C4's have valves that control the heat and some don't, I may be wrong.
Does your car have the digital a/c controller or does it have the old slide type temperature adjustment? The digital A/C controller is called a C68 and has buttons for up and down temperature. If you have a C68 you might have an issue with the Blend door which is what determines what temperature air goes where. The Blending devices frequently have problems but are fairly easily fixed. The Factory Service Manual (FSM) set would be very helpful in diagnosing a problem like this, If you don't have one then you ought to do that right away, be sure to get the proper year so it can help you. The manuals are available in Print or on DVD. Do not use anything BUT the FSM's as the rest are worthless (imo) and don't have the specific knowledge that the FSM's do contain.
Tell us about the car that is having the issues, please! Then the real diagnostic help starts popping up here on this Forum a there are a lot of years of Corvette experience available on this Forum and most of the members only want to help you solve your issues.
We are glad to help in any way we can, we just need to know what Corvette you own!
Have a great day!
We need to know more about the Corvette that we are talking about. You need to provide more information so people can help you determine why you have no heat. Some C4's have valves that control the heat and some don't, I may be wrong.
Does your car have the digital a/c controller or does it have the old slide type temperature adjustment? The digital A/C controller is called a C68 and has buttons for up and down temperature. If you have a C68 you might have an issue with the Blend door which is what determines what temperature air goes where. The Blending devices frequently have problems but are fairly easily fixed. The Factory Service Manual (FSM) set would be very helpful in diagnosing a problem like this, If you don't have one then you ought to do that right away, be sure to get the proper year so it can help you. The manuals are available in Print or on DVD. Do not use anything BUT the FSM's as the rest are worthless (imo) and don't have the specific knowledge that the FSM's do contain.
Tell us about the car that is having the issues, please! Then the real diagnostic help starts popping up here on this Forum a there are a lot of years of Corvette experience available on this Forum and most of the members only want to help you solve your issues.
We are glad to help in any way we can, we just need to know what Corvette you own!
Have a great day!
I have a 95 with the digital controller and replaced the blend door last night
Hello again,
Since you have a C68 and I am not familiar with the 1995 models you might try asking Bryan at BATEE.COM as he knows the heater control system very well. This is the direction I would go as Bryan is a tremendous resource to the Corvette World.
Have you followed the two heater hoses towards the firewall? If there is a Hot water shutoff valve that is where it would be I believe. Just a thought....
You will have heat again... The "right" person with the specific knowledge will be along soon! That is one of the beauty's of this Forum....
Again, I wish you the very best in solving this wacky issue!
If the heater core is plugged, won't one of the hoses be cold while the other gets warm slowly? Maybe it would be easier to crimp off the heater hoses and try to flush it? Backflushed another car and a bunch of gunk came out and I got heat again.
If the heater core is plugged, won't one of the hoses be cold while the other gets warm slowly? Maybe it would be easier to crimp off the heater hoses and try to flush it? Backflushed another car and a bunch of gunk came out and I got heat again.
I had to do the same on my '93 recently a bit of gunk came out and then heat working. Hot water is always circulating through the heater core and there is a restricter in the line that is flow dependant ( as the flow increases due to higher engine revs it closes up but not completely). My theory is because of this more gentle flow any gunk in the system will accumulate in the heater core. FWIW I couldn't tell by touching the heater hoses that there was no flow through the core, both hoses felt the same.
You said you replaced the blender door. I presume that you replaced the blender door actuator, correct?
you said air vent location changes correctly when selected, fan works, and blender door moves(I presumed that you verify that door moves all the way from colt to warm through evaprator opening - door didn’t move completely to heat position on my 95 after blender door actuator was replaced, only gave out lukewarm heat), and other obvious things are checked - like make sure that core isn’t leaking or filled with air, then I think likely cause of you not getting heat would be heatercore itself.
there are two hoses coming ouT of heater core - inlet and outlet hose. Once car is up to operating temp, both of these hoses should be hot. If not, there is likely a clog.
very common for these cars to be only driven in summer, and heat never gets used, and it clogs up.
had this happened on my old z28 and TransAm I had.
Yes the blend door actuator was replaced. and when this all started I checked the inlet outlet hose and both were hot. What about the programmer could it be that?
We need to know how you verified the blend door was moving? The later cars, including yours are constant flow. Even in the summer with A/C on lowest temp, water is flowing through the core. If coolant is maintained clogging is unlikely. but if you just bought the car someone could have changed out neglected coolant. I've also seen bypassed cores where the hoses would be hot because a bypass tube was way back under the firewall. Have you visually verified that the hoses are connected to the heater core?
It seems odd that you said the blend door moves to hot and the hoses are hot but no hot air. The only thing I can see causing that is a heater core clogged with something on the outside forcing air to go around rather than through. But that should caused greatly reduced air flow.
Have you run the diagnostics on the HVAC controller?
OP, if you haven't checked your blender door action visibly, here is good pictures.
one of my issue with my C4 was that door didn’t move all the way from Colt to hot after blender motor was replaced, because I “clocked” it when I forced it to move.
so it only went about 1/4 of way to heat.
Originally Posted by mwm1993
I replaced my blend door actuator yesterday and wanted to add some of my pics to this thread to possibly help with diagnosis. By the way mine did not throw any codes. I thought a failed blend door actuator might give a 01 or 02.
If you removed the 3 7mm bolts on this thing it will come out:
You can then shine a light down this "sight window" and see the blend door very clearly. The blend door is on the left of this picture
Then I put my phone down into the box to snap a better pic of the blend door:
If you have the blower running and cycle the temperature from hot to cold the blend door should open and close and if it does not then the problem might be the actuator. Here is mine once it was out. It did have a little bit of water in it
The door moves watched it.. too the hoses go into the firewall are cooler then the large radiator hoses and one is even cooler then the other . The only thing I see in the line is picture. no idea air has to go through the HC I'm going to check for blockages this weekend. how has people flushed it before? The door moves. did the battery disconnect and heard it move. too the hoses go into the firewall ar cooler then the large radiator hoses and one is even cooler then the other . The only thing I see in the line is picture.
Last edited by temcgregor; Nov 27, 2018 at 08:51 PM.
NO Heat
