No Heat
12-24-2014, 08:51 AM
#22
Intermediate
12-24-2014, 01:11 PM
#23
heat and air
afgunn I have a 1996 that currently only blows only from the defroster and floor vents, even using the air conditioner the cold air comes out of the defroster and floot vents. For the last couple years on a trip using the air conditioning after about 15 minutes on the road trip it would change blowing air out of the vents for normal air conditioning selection. Stop the car on the trip and the air conditioning would again come out of the defroster and floor vents cold until on the road again for about 15 minutes. The heat selection works fine, but comes out of the defroster and floor vents even though defroster was not selected.
In my search I believe I have found my problem. The Control Unit for the air distribution selections is on the drivers side mounted on the firewall above the gas pedal from what I have understood. The Control unit has nipples coming out of it that vacuum hoses connect to that supply vacuum to operate the vacuum motors for heater, defroster, and air conditioning. The nipples were reported in my search to collapse and prevent appropriate vacuum distribution.
I have went no farther in doing anything about the Control Unit since I read about the problem with it.
Did also read that the vacuum valve replacement mentioned I other posts on the passenger side of the engine is good if the cruise control which uses vacuum performs okay. Mine cruise works great like it always has since my 1996 was new.
My 1996 does have the electronic air conditioning and heating unit.
With the system turned off when driving my 1996 I can feel just a little bit of heated air coming from the floor vents and defroster outlet driving the highway roads.
I have checked for codes using the control panel and every time it reads no codes.
In my search I believe I have found my problem. The Control Unit for the air distribution selections is on the drivers side mounted on the firewall above the gas pedal from what I have understood. The Control unit has nipples coming out of it that vacuum hoses connect to that supply vacuum to operate the vacuum motors for heater, defroster, and air conditioning. The nipples were reported in my search to collapse and prevent appropriate vacuum distribution.
I have went no farther in doing anything about the Control Unit since I read about the problem with it.
Did also read that the vacuum valve replacement mentioned I other posts on the passenger side of the engine is good if the cruise control which uses vacuum performs okay. Mine cruise works great like it always has since my 1996 was new.
My 1996 does have the electronic air conditioning and heating unit.
With the system turned off when driving my 1996 I can feel just a little bit of heated air coming from the floor vents and defroster outlet driving the highway roads.
I have checked for codes using the control panel and every time it reads no codes.
Last edited by 70ZZ3 96LT4; 12-24-2014 at 01:13 PM.
12-24-2014, 01:24 PM
#24
Instructor
Thread Starter
afgunn I have a 1996 that currently only blows only from the defroster and floor vents, even using the air conditioner the cold air comes out of the defroster and floot vents. For the last couple years on a trip using the air conditioning after about 15 minutes on the road trip it would change blowing air out of the vents for normal air conditioning selection. Stop the car on the trip and the air conditioning would again come out of the defroster and floor vents cold until on the road again for about 15 minutes. The heat selection works fine, but comes out of the defroster and floor vents even though defroster was not selected.
In my search I believe I have found my problem. The Control Unit for the air distribution selections is on the drivers side mounted on the firewall above the gas pedal from what I have understood. The Control unit has nipples coming out of it that vacuum hoses connect to that supply vacuum to operate the vacuum motors for heater, defroster, and air conditioning. The nipples were reported in my search to collapse and prevent appropriate vacuum distribution.
I have went no farther in doing anything about the Control Unit since I read about the problem with it.
Did also read that the vacuum valve replacement mentioned I other posts on the passenger side of the engine is good if the cruise control which uses vacuum performs okay. Mine cruise works great like it always has since my 1996 was new.
My 1996 does have the electronic air conditioning and heating unit.
With the system turned off when driving my 1996 I can feel just a little bit of heated air coming from the floor vents and defroster outlet driving the highway roads.
I have checked for codes using the control panel and every time it reads no codes.
In my search I believe I have found my problem. The Control Unit for the air distribution selections is on the drivers side mounted on the firewall above the gas pedal from what I have understood. The Control unit has nipples coming out of it that vacuum hoses connect to that supply vacuum to operate the vacuum motors for heater, defroster, and air conditioning. The nipples were reported in my search to collapse and prevent appropriate vacuum distribution.
I have went no farther in doing anything about the Control Unit since I read about the problem with it.
Did also read that the vacuum valve replacement mentioned I other posts on the passenger side of the engine is good if the cruise control which uses vacuum performs okay. Mine cruise works great like it always has since my 1996 was new.
My 1996 does have the electronic air conditioning and heating unit.
With the system turned off when driving my 1996 I can feel just a little bit of heated air coming from the floor vents and defroster outlet driving the highway roads.
I have checked for codes using the control panel and every time it reads no codes.
I have gotten a lot of input lately, but I have just not had the time to check things out due to the season that it is.
God Bless!
12-25-2014, 03:56 AM
#25
Race Director
https://www.corvetteforum.com/forums...post1580705187
Some people cut the tips off the nipples and I have heard of someone who swapped in a 1995 unit to fix his.
I read an article several years ago from a guy who fixed his by putting stiff plastic tubing inside his nipples to keep them from collapsing. I vaguely recollect that he used the plastic tubing from an ink pen cartridge.
12-27-2014, 10:56 PM
#26
Instructor
Thread Starter
Checked this item out today. Had vacuum out both nipples, so I believe that this item is working?
02-22-2015, 05:58 PM
#27
Instructor
Thread Starter
I have helped many with this common C4 issue. My 95 coupe had the same symptoms and I checked out the basics as you have.
The problem is probably the damper door electric actuator motor on the the heater/ac box under the passenger knee bolster. To check it out easily from under the hood, take the small top plate off the heater box near the fan motor housing. You will also see a electric harness attached to this plate, but it will allow you a look into the heater box and the metal damper door (about 4X6) that separates the A/c front side from the back heater core in the back . Move the heater controls and this damper door will probably reveal is does not swing with A/c and heat settings. This is why you have little or no heat - it is stuck.
Next is to remove the knee bolster by exposing the fuse panel cover and carefully pulling the bolster towards you. The bolster has 4 plastic tabs on the front and these are quite brittle so go slow. Now at the bottom of the heater box you will see the heater temperature valve (Ecklers #51595, $100). Remove this with 2 bolts and now see if the motor is seized up by trying different heat- A/c settings. I'd bet yours is frozen from internal corrosion like mine was. Now turn the shaft that goes into the heater box and swing the damper door. You should now feel heat.
You may want to check out my postings on the C action forum site (John6277) on this topic.
One final note, don't be temped to buy the $50 cheaper Dorman motor as it is a very poor fit. All the best to you Merry Christmas.
The problem is probably the damper door electric actuator motor on the the heater/ac box under the passenger knee bolster. To check it out easily from under the hood, take the small top plate off the heater box near the fan motor housing. You will also see a electric harness attached to this plate, but it will allow you a look into the heater box and the metal damper door (about 4X6) that separates the A/c front side from the back heater core in the back . Move the heater controls and this damper door will probably reveal is does not swing with A/c and heat settings. This is why you have little or no heat - it is stuck.
Next is to remove the knee bolster by exposing the fuse panel cover and carefully pulling the bolster towards you. The bolster has 4 plastic tabs on the front and these are quite brittle so go slow. Now at the bottom of the heater box you will see the heater temperature valve (Ecklers #51595, $100). Remove this with 2 bolts and now see if the motor is seized up by trying different heat- A/c settings. I'd bet yours is frozen from internal corrosion like mine was. Now turn the shaft that goes into the heater box and swing the damper door. You should now feel heat.
You may want to check out my postings on the C action forum site (John6277) on this topic.
One final note, don't be temped to buy the $50 cheaper Dorman motor as it is a very poor fit. All the best to you Merry Christmas.
I still have the air delivery problem, where the air will only blow out of the heater ducts and defrost and will not change. I have vacuum inside the car up to the passenger knee bolster - have not been able to check any further yet.
02-22-2015, 06:00 PM
#28
Instructor
Thread Starter
Also make sure you don't have any air in the system. Like in another post and I had a similar problem and turned out to be the black expansion tank. My heater hoses were also both hot too.
The problem I had was it leaked antifreeze (very little) at the neck but mostly it let air in the system and therefore no heat.
Yes, your problem may be different because I didn't have the blowing of air just out the floor and defrost outlet. That could be a possible vacuum leak causing this.
Hope this helps.
The problem I had was it leaked antifreeze (very little) at the neck but mostly it let air in the system and therefore no heat.
Yes, your problem may be different because I didn't have the blowing of air just out the floor and defrost outlet. That could be a possible vacuum leak causing this.
Hope this helps.
02-24-2015, 01:12 PM
#29
Burning Brakes
02-25-2015, 01:58 AM
#31
Race Director
The vacuum needs to get to the HVAC programmer, which is located on the firewall above the gas pedal. The vacuum source is a black plastic tube.
The "relays clicking" that you hear is the vacuum solenoids. They route the vacuum to the various actuators that determine where the air comes out of the dash.
The "relays clicking" that you hear is the vacuum solenoids. They route the vacuum to the various actuators that determine where the air comes out of the dash.
02-25-2015, 07:43 AM
#32
Instructor
Thread Starter
The vacuum needs to get to the HVAC programmer, which is located on the firewall above the gas pedal. The vacuum source is a black plastic tube.
The "relays clicking" that you hear is the vacuum solenoids. They route the vacuum to the various actuators that determine where the air comes out of the dash.
The "relays clicking" that you hear is the vacuum solenoids. They route the vacuum to the various actuators that determine where the air comes out of the dash.