Heater core has me steamed
Thread Starter
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
Likes: 1,174
From: Southlake, TX
Heater core has me steamed
Hey All!
I've had my 82 for a couple of weeks now and am fixing her a little at a time. This is my second C3 (I had a 77) and I'm having a great time with it.
I now have a problem that has me stumped- really.
I replaced the heater core on my AC car. The repair went smooth but when I go to turn the heat on, I can only get a brief (3 second) "pop" of heater air before it returns to ambient temperature. I'll have the temp setting on cold and move it to heat-- I'll get a quick rush of hot air then it cools rapidly.
The AC system works as it should.
I've replaced the core, all hoses and the water shut off valve. I've checked the vacuum and replaced the control panel. I thought there might be some trapped air so I worked to make sure that there was no trapped air in the system.
Anyone else have this problem? Fortunately summer is approaching and I've got a little time!
I've had my 82 for a couple of weeks now and am fixing her a little at a time. This is my second C3 (I had a 77) and I'm having a great time with it.
I now have a problem that has me stumped- really.
I replaced the heater core on my AC car. The repair went smooth but when I go to turn the heat on, I can only get a brief (3 second) "pop" of heater air before it returns to ambient temperature. I'll have the temp setting on cold and move it to heat-- I'll get a quick rush of hot air then it cools rapidly.
The AC system works as it should.
I've replaced the core, all hoses and the water shut off valve. I've checked the vacuum and replaced the control panel. I thought there might be some trapped air so I worked to make sure that there was no trapped air in the system.
Anyone else have this problem? Fortunately summer is approaching and I've got a little time!
Race Director
Joined: Oct 2000
Posts: 12,683
Likes: 3,137
From: Shamong, NJ
It sounds like you have a problem with one of the flapper doors, that direct the air from heat, to vent, to defrost, to AC.
I would guess that your problem has something to do with one of the vacuum lines that control the different doors in the heater box. One may be routed wrong or pinched, or maybe something is binding, preventing a door from working properly?
I would guess that your problem has something to do with one of the vacuum lines that control the different doors in the heater box. One may be routed wrong or pinched, or maybe something is binding, preventing a door from working properly?
Thread Starter
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
Likes: 1,174
From: Southlake, TX
Thanks- possibly I'll re check. However all the air diverts correctly for defrost, heat and vent modes.
There seems to be the "interior/exterior" vent doors that may be messed up. This could effecting things?
The
There seems to be the "interior/exterior" vent doors that may be messed up. This could effecting things?
The
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You really need a copy of the AIM and a copy of the Chevrolet Chassis Service Manual for your car. The AIM will show drawings of the heater/a-c controls and the vacuum connections for that HVAC system; the CCSM has the detail on the HVAC controls strategy/logic.
If you study BOTH, you will gain needed knowledge to trouble-shoot your system and find the problem. I believe that your problem is likely associated with 1) a damper door and/or actuator that is preventing warm air from entering the passenger compartment or 2) there is a problem with the HVAC control head not 'calling' for heat when it should.
LEARN how it is supposed to work; then test to find what is NOT working as it should. Be aware that there may be separate little switches that are actuated with the movement of the HVAC control levers. One of them could be defective or out of adjustment.
If you study BOTH, you will gain needed knowledge to trouble-shoot your system and find the problem. I believe that your problem is likely associated with 1) a damper door and/or actuator that is preventing warm air from entering the passenger compartment or 2) there is a problem with the HVAC control head not 'calling' for heat when it should.
LEARN how it is supposed to work; then test to find what is NOT working as it should. Be aware that there may be separate little switches that are actuated with the movement of the HVAC control levers. One of them could be defective or out of adjustment.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The temperature control for then 1977 - 1982 Cars is controlled by a cable that is attached directly to the lever in the heater control. If the cable isn't adjusted properly what will happen is the lever (and cable) will pull back on it's own... can you see the lever moving on the control? If this is the case then
The adjustment is as follows... With the temperature control properly connected, move the temperature control lever to the extreme cool position. There should be .100 +/- .020 gap between the edge of the opening and the side of the lever. Adjustment is accomplished by rotating the cable turnbuckle to lengthen or shorten the cable.
-Willcox
The adjustment is as follows... With the temperature control properly connected, move the temperature control lever to the extreme cool position. There should be .100 +/- .020 gap between the edge of the opening and the side of the lever. Adjustment is accomplished by rotating the cable turnbuckle to lengthen or shorten the cable.
-Willcox
Last edited by Willcox Corvette; Mar 6, 2016 at 11:30 PM.
Thread Starter
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
Likes: 1,174
From: Southlake, TX
Thanks Everyone! I appreciate your help! Couple of things...
1) I have the official GM Corvette service Manual. This was my first purchase. While I'm a noob with Vettes, I have taken apart dozens of Mopar B bodies and the service manual always saved me.
2) I believe the Heater cable attached and adjusted properly- the actuator "push in" on cold to disengage the water valve. I checked the vacuum from the and it all works as it should at the water valve. Funny as I have a different (square, cream colored unit) heat vacuum unit rather than the ones everyone sees that is more of a cylinder. huh.
3) I did notice that I had a actuator that was not working. It was the air flapper door (green vacuum line) located on the passenger side of the firewall and in between the fender. I looks like it is the on/off to the outside air right by the fan. This actuator was stuck, so I took it apart, cleaned it and now it works as it should. I have not tested/fixed the vacuum lines.
Could this door be the problem as it would let in outside air when stuck open and overwhelm the heater core? I'll be able to test/fix screw up these vacuum lines Thursday after work!
Thanks!
1) I have the official GM Corvette service Manual. This was my first purchase. While I'm a noob with Vettes, I have taken apart dozens of Mopar B bodies and the service manual always saved me.
2) I believe the Heater cable attached and adjusted properly- the actuator "push in" on cold to disengage the water valve. I checked the vacuum from the and it all works as it should at the water valve. Funny as I have a different (square, cream colored unit) heat vacuum unit rather than the ones everyone sees that is more of a cylinder. huh.
3) I did notice that I had a actuator that was not working. It was the air flapper door (green vacuum line) located on the passenger side of the firewall and in between the fender. I looks like it is the on/off to the outside air right by the fan. This actuator was stuck, so I took it apart, cleaned it and now it works as it should. I have not tested/fixed the vacuum lines.
Could this door be the problem as it would let in outside air when stuck open and overwhelm the heater core? I'll be able to test/fix screw up these vacuum lines Thursday after work!
Thanks!
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Yes. That could be your primary problem. But, you should still understand all the actions performed by the HVAC system and what makes them function, if you want to be sure that it is all up to par.
Sounds like you are well on your way to sorting things out.
Sounds like you are well on your way to sorting things out.
Thread Starter
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
Likes: 1,174
From: Southlake, TX
Well, I'm feeling stumped.
I followed the system to the letter according to the AIM. I tested all diaphragms, hoses for leaks, routing...etc.
The A/C Works perfectly and in all modes. The vents are all working as they should. The heat still *puufs* in all setting then gets progressively cooler and more ambient. I slide the level to cool for about 5 seconds, then back to heat and get that quick blast of super heated air, then the slow fade (if I keep sliding back and forth, the system would stay warm!)
Any ideas?
I read how some guys have nothing but hot air all the time-- I have the same problem but in reverse!
Could my can just be "cold blooded" and need a hotter thermostat?
I followed the system to the letter according to the AIM. I tested all diaphragms, hoses for leaks, routing...etc.
The A/C Works perfectly and in all modes. The vents are all working as they should. The heat still *puufs* in all setting then gets progressively cooler and more ambient. I slide the level to cool for about 5 seconds, then back to heat and get that quick blast of super heated air, then the slow fade (if I keep sliding back and forth, the system would stay warm!)
Any ideas?
I read how some guys have nothing but hot air all the time-- I have the same problem but in reverse!
Could my can just be "cold blooded" and need a hotter thermostat?
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
I've not owned an '82, but I can tell you why early year C3's have the symptoms you described. There is a weatherstrip-like seal at the rear of the hood; it seals the heat in the engine compartment from 'getting loose' and leaking at the base of the windshield. If that seal is bad, the engine heat has a direct path into the passenger compartment air inlet door, which is under the cowl area on the right side of the windshield. And that heat can override whatever the HVAC system is requiring.
In addition, the seal on the vent door at the right-side kickpanel is likely worn out and/or completely missing. Any hot, ingested engine compartment air will get directed through that kick panel vent door into the passenger area. So, even if that door is closed by the HVAC system, the bad/missing seal on that door will just allow all that heat to bypass it.
Fix the seal at the rear of the hood (check the AIM for 1982; it should show that seal...if there should be one), and fix the seal on that vent door; then you may have better results from your HVAC system.
P.S. If you need to rebuild the seal on that kickpanel door, PM me for inexpensive (but almost identical to factory) method to fix it.
In addition, the seal on the vent door at the right-side kickpanel is likely worn out and/or completely missing. Any hot, ingested engine compartment air will get directed through that kick panel vent door into the passenger area. So, even if that door is closed by the HVAC system, the bad/missing seal on that door will just allow all that heat to bypass it.
Fix the seal at the rear of the hood (check the AIM for 1982; it should show that seal...if there should be one), and fix the seal on that vent door; then you may have better results from your HVAC system.
P.S. If you need to rebuild the seal on that kickpanel door, PM me for inexpensive (but almost identical to factory) method to fix it.