Heater not blowing warm air
Thread Starter
Intermediate
Joined: Nov 2011
Posts: 31
Likes: 0
From: TN
Heater not blowing warm air
The coolant temperature went up to 250° the heater then was blowing cold air. When I started driving the coolant temperature went back down to 205° and the heater is blowing correctly.
Coolant temp is now showing 246deg and the blower is blowing cold air at idle. But when I have power going to the engine, the heater will blow warm.
I am assuming it is a sensor??? Solar Flares??
Thanks
Coolant temp is now showing 246deg and the blower is blowing cold air at idle. But when I have power going to the engine, the heater will blow warm.
I am assuming it is a sensor??? Solar Flares??
Thanks
Drifting
Joined: Feb 2010
Posts: 1,720
Likes: 38
From: Colorado
unless the two are somehow related, my heater doesnt blow warm either, and it's a stuck flapper door. already know that, and i just dont wanna fix it. i'm in AL though, so its almost never freezing here, anyway.
if you have sensor gremlins, i suppose it could be related. the coolant temp sensor is on the driver side, towards the front of the engine, just under the head. can check that connection for corrosion, trace the wire back, replace it if you want (it's cheap, but i was chastised last time i suggested replacing a $20 part here, so take that advice how you wish).
the actual instructions for troubleshooting the temp sensors being out of whack is tedious. involves a multimeter and a lot of time. it's been posted here a few times, but i'd have to search to find it myself.
if you have sensor gremlins, i suppose it could be related. the coolant temp sensor is on the driver side, towards the front of the engine, just under the head. can check that connection for corrosion, trace the wire back, replace it if you want (it's cheap, but i was chastised last time i suggested replacing a $20 part here, so take that advice how you wish).
the actual instructions for troubleshooting the temp sensors being out of whack is tedious. involves a multimeter and a lot of time. it's been posted here a few times, but i'd have to search to find it myself.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
WELL,,,,,,,,,,,,,,,, The temp output is controlled by moving BLEND DOORS What HVAC system do you have?? Dual Zone or manual.
The doors are moved by electric actuators.
Read your DTCs and see if you have any HVAC related DTCs that are associated with the actuators. (DUAL ZONE only)
Manual HVAC does not monitor the actuator operation or HVAC functions.
The doors either cover the heat or cooling coils or expose a combo of both to get air somewhere in between.
You need to see if the electric actuator is properly responding to the movement of the temp ****.
Bill
The doors are moved by electric actuators.
Read your DTCs and see if you have any HVAC related DTCs that are associated with the actuators. (DUAL ZONE only)
Manual HVAC does not monitor the actuator operation or HVAC functions.
The doors either cover the heat or cooling coils or expose a combo of both to get air somewhere in between.
You need to see if the electric actuator is properly responding to the movement of the temp ****.
Bill
Thread Starter
Intermediate
Joined: Nov 2011
Posts: 31
Likes: 0
From: TN
WELL,,,,,,,,,,,,,,,, The temp output is controlled by moving BLEND DOORS What HVAC system do you have?? Dual Zone or manual.
The doors are moved by electric actuators.
Read your DTCs and see if you have any HVAC related DTCs that are associated with the actuators. (DUAL ZONE only)
Manual HVAC does not monitor the actuator operation or HVAC functions.
The doors either cover the heat or cooling coils or expose a combo of both to get air somewhere in between.
You need to see if the electric actuator is properly responding to the movement of the temp ****.
Bill
The doors are moved by electric actuators.
Read your DTCs and see if you have any HVAC related DTCs that are associated with the actuators. (DUAL ZONE only)
Manual HVAC does not monitor the actuator operation or HVAC functions.
The doors either cover the heat or cooling coils or expose a combo of both to get air somewhere in between.
You need to see if the electric actuator is properly responding to the movement of the temp ****.
Bill
Thread Starter
Intermediate
Joined: Nov 2011
Posts: 31
Likes: 0
From: TN
Melting Slicks
Joined: Sep 2011
Posts: 2,258
Likes: 544
From: Appleton WI
What concerns me is your temp gage is reading hot and you're not getting hot air out of the HVAC. Then you say you rev the engine and the temp goes down and you get heat.
The first thing that comes to mind is you are either low on coolant or have an air bubble. Double check this first so you don't blow your engine doing diagnostics. Did you recently do a coolant change or replace / repair something in the coolant system? What is the rest of the story?
A little tip most people don't know. If your car is overheating, you can turn up the temp on the HVAC controller and turn the fan on high to help cool the engine down. (Warning: it will be VERY hot air so set the air to blow out the dash vents and open your windows.) That can be enough to allow you to drive the car to a safe place to park. If during that time the heat stops coming out of the vents, SHUT IT DOWN because you're out of coolant.
The reason this works is because the heater core that provides heat to the cabin is a smaller version of the radiator in the front of the car.
The first thing that comes to mind is you are either low on coolant or have an air bubble. Double check this first so you don't blow your engine doing diagnostics. Did you recently do a coolant change or replace / repair something in the coolant system? What is the rest of the story?
A little tip most people don't know. If your car is overheating, you can turn up the temp on the HVAC controller and turn the fan on high to help cool the engine down. (Warning: it will be VERY hot air so set the air to blow out the dash vents and open your windows.) That can be enough to allow you to drive the car to a safe place to park. If during that time the heat stops coming out of the vents, SHUT IT DOWN because you're out of coolant.
The reason this works is because the heater core that provides heat to the cabin is a smaller version of the radiator in the front of the car.
Last edited by 3sACROWD; Mar 15, 2013 at 02:57 PM. Reason: added driving tip
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Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 302
From: Columbia SC
A recent post had a similar issue but not exactly the same. He was not overheating, but could not get warm air from the heater. Ended up his surge tank was low. He flushed his system and put in new coolant. It was either low coolant and/or air in the system. Might check that also. As I recall Bill Curlee was the "main man" on that one too.
http://forums.corvetteforum.com/c5-t...ways-cold.html
http://forums.corvetteforum.com/c5-t...ways-cold.html
Last edited by dadaroo; Mar 16, 2013 at 12:09 PM. Reason: Add link
Thread Starter
Intermediate
Joined: Nov 2011
Posts: 31
Likes: 0
From: TN
What concerns me is your temp gage is reading hot and you're not getting hot air out of the HVAC. Then you say you rev the engine and the temp goes down and you get heat.
The first thing that comes to mind is you are either low on coolant or have an air bubble. Double check this first so you don't blow your engine doing diagnostics. Did you recently do a coolant change or replace / repair something in the coolant system? What is the rest of the story?
A little tip most people don't know. If your car is overheating, you can turn up the temp on the HVAC controller and turn the fan on high to help cool the engine down. (Warning: it will be VERY hot air so set the air to blow out the dash vents and open your windows.) That can be enough to allow you to drive the car to a safe place to park. If during that time the heat stops coming out of the vents, SHUT IT DOWN because you're out of coolant.
The reason this works is because the heater core that provides heat to the cabin is a smaller version of the radiator in the front of the car.
The first thing that comes to mind is you are either low on coolant or have an air bubble. Double check this first so you don't blow your engine doing diagnostics. Did you recently do a coolant change or replace / repair something in the coolant system? What is the rest of the story?
A little tip most people don't know. If your car is overheating, you can turn up the temp on the HVAC controller and turn the fan on high to help cool the engine down. (Warning: it will be VERY hot air so set the air to blow out the dash vents and open your windows.) That can be enough to allow you to drive the car to a safe place to park. If during that time the heat stops coming out of the vents, SHUT IT DOWN because you're out of coolant.
The reason this works is because the heater core that provides heat to the cabin is a smaller version of the radiator in the front of the car.
Thread Starter
Intermediate
Joined: Nov 2011
Posts: 31
Likes: 0
From: TN
A recent post had a similar issue but not exactly the same. He was not overheating, but could not get warm air from the heater. Ended up his surge tank was low. He flushed his system and put in new coolant. It was either low coolant and/or air in the system. Might check that also. As I recall Bill Curlee was the "main man" on that one too.
http://forums.corvetteforum.com/c5-t...ways-cold.html
http://forums.corvetteforum.com/c5-t...ways-cold.html
Melting Slicks
Joined: Oct 2008
Posts: 3,200
Likes: 69
From: DC
St. Jude Donor '09-'10
Go into diagnostic mode and hold down the reset button on 99 HVAC. Do you hear the doors moving? Does it throw any codes afterwards?
Thread Starter
Intermediate
Joined: Nov 2011
Posts: 31
Likes: 0
From: TN
That's what I did and it fixed my problem. If that doesn't work, the next step I was planning on doing was checking if the heater core is clogged. Fortunately I didn't have to go that far.
Go into diagnostic mode and hold down the reset button on 99 HVAC. Do you hear the doors moving? Does it throw any codes afterwards?
Go into diagnostic mode and hold down the reset button on 99 HVAC. Do you hear the doors moving? Does it throw any codes afterwards?
Thread Starter
Intermediate
Joined: Nov 2011
Posts: 31
Likes: 0
From: TN
What concerns me is your temp gage is reading hot and you're not getting hot air out of the HVAC. Then you say you rev the engine and the temp goes down and you get heat.
The first thing that comes to mind is you are either low on coolant or have an air bubble. Double check this first so you don't blow your engine doing diagnostics. Did you recently do a coolant change or replace / repair something in the coolant system? What is the rest of the story?
A little tip most people don't know. If your car is overheating, you can turn up the temp on the HVAC controller and turn the fan on high to help cool the engine down. (Warning: it will be VERY hot air so set the air to blow out the dash vents and open your windows.) That can be enough to allow you to drive the car to a safe place to park. If during that time the heat stops coming out of the vents, SHUT IT DOWN because you're out of coolant.
The reason this works is because the heater core that provides heat to the cabin is a smaller version of the radiator in the front of the car.
The first thing that comes to mind is you are either low on coolant or have an air bubble. Double check this first so you don't blow your engine doing diagnostics. Did you recently do a coolant change or replace / repair something in the coolant system? What is the rest of the story?
A little tip most people don't know. If your car is overheating, you can turn up the temp on the HVAC controller and turn the fan on high to help cool the engine down. (Warning: it will be VERY hot air so set the air to blow out the dash vents and open your windows.) That can be enough to allow you to drive the car to a safe place to park. If during that time the heat stops coming out of the vents, SHUT IT DOWN because you're out of coolant.
The reason this works is because the heater core that provides heat to the cabin is a smaller version of the radiator in the front of the car.
Le Mans Master
Joined: Mar 2002
Posts: 8,466
Likes: 51
St. Jude Donor '17
Did you run the DIC codes as suggested multiple times?
DO you know how to?
If you have dual zone is one side of the air cold and the other side warmer?
Last edited by Got uid0; Mar 18, 2013 at 06:46 PM.