Heater is always On
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Heater is always On
Hey Guys,
My 97 960 has the heater always blowing regardless of any of the settings on the ECC. The fan could be on 0 and it will still have hot air coming out. When I put the fan speed at 5 its the same hot air just coming out faster.
This is regardless of the temperature settings. It could be on 64 or 84, it will always be hot air. Recirc or even turning the AC off doesn't do anything.
Any help would be appreciated. This was great in the winter, but now its starting to get very annoying.
My 97 960 has the heater always blowing regardless of any of the settings on the ECC. The fan could be on 0 and it will still have hot air coming out. When I put the fan speed at 5 its the same hot air just coming out faster.
This is regardless of the temperature settings. It could be on 64 or 84, it will always be hot air. Recirc or even turning the AC off doesn't do anything.
Any help would be appreciated. This was great in the winter, but now its starting to get very annoying.
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Remove your glove box, and look to the left, you should see a servo attached to a white arm. This is what changes the air mix. If you turn the temp dial, does this arm move at all? there is a chase it could be jammed or just gone bad.
Also, by constantly hot, do you mean that the air is always blowing, or do you mean that when the setting is to "0" hot air kinda just radiates out of the vents?
Also, by constantly hot, do you mean that the air is always blowing, or do you mean that when the setting is to "0" hot air kinda just radiates out of the vents?
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Remove your glove box, and look to the left, you should see a servo attached to a white arm. This is what changes the air mix. If you turn the temp dial, does this arm move at all? there is a chase it could be jammed or just gone bad.
Also, by constantly hot, do you mean that the air is always blowing, or do you mean that when the setting is to "0" hot air kinda just radiates out of the vents?
Also, by constantly hot, do you mean that the air is always blowing, or do you mean that when the setting is to "0" hot air kinda just radiates out of the vents?
It's not really blowing at 0. More like you described radiating out. But it's not warm air. It's actual HOT air.
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Ah, as I thought. Your likely problem is that servo motor I had mentioned, I circled it in the attached photo along with the linkage that attaches it to the door that switched between hot and cold air.
Also check along your fire wall engine side. Look for where the heater hoses go into the fire wall. On my 1995 there is a vacuum controlled valve that I am guessing you have also. Maybe close that off with some zipties or something along those lines.
Also check along your fire wall engine side. Look for where the heater hoses go into the fire wall. On my 1995 there is a vacuum controlled valve that I am guessing you have also. Maybe close that off with some zipties or something along those lines.
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I also suggest checking the heater valve. The heater valve should be closing when you have the temperature set all the way cold. You can see it on the firewall by the heater hoses, there is a little arm that pulls in when it closes.
My car had both a leaky vacuum bellows AND the solenoid board had to be re-soldered. I think the mix door has been working fine, but I still got hot air conditioner when the vacuum mess wasn't working.
My car had both a leaky vacuum bellows AND the solenoid board had to be re-soldered. I think the mix door has been working fine, but I still got hot air conditioner when the vacuum mess wasn't working.
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Ah, as I thought. Your likely problem is that servo motor I had mentioned, I circled it in the attached photo along with the linkage that attaches it to the door that switched between hot and cold air.
Also check along your fire wall engine side. Look for where the heater hoses go into the fire wall. On my 1995 there is a vacuum controlled valve that I am guessing you have also. Maybe close that off with some zipties or something along those lines.
Also check along your fire wall engine side. Look for where the heater hoses go into the fire wall. On my 1995 there is a vacuum controlled valve that I am guessing you have also. Maybe close that off with some zipties or something along those lines.
This little car has gremlins in it. All weekend the AC worked perfectly fine, and the heat never came on
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How would i know if the valve is faulty? Will check it out next time the car starts blowing hot air at 0
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Finally if it is always open (no vacuum) you will need to test the vac line to see if its leaking
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Pretty much what Nick says but this may help clarify.
As long as the ignition is ON, the ECC should be controlling the heater valve and mix door. The goal for it is to get the temperature in the cabin moving towards the "thermostat setting." It will look at the cabin temp sensor and the sunlight sensor to try and figure out how warm the air should be. This happens at all times regardless of the fan setting, as long as the ignition is on.
To override this control system and control the heater valve and mix doors manually, set the thermostat control to the red dot (heater valve open) or the blue dot (heater valve closed.)
The normal/resting position for the heater valve is "open" or hot. The heater valve has a vacuum bellows in it (cylinder) and there is a protruding arm with a link to the actual valve lever. Observe it in the rest position. You should be able to put your finger on it and push the arm into the cylinder. When vacuum is applied to the cylinder, the arm will retract fully. When you get used to how it looks, you will be able to tell if it is open or closed by looking at the arm. Of course you can also test it with a vacuum pump if you like. (My valve leaked water so I replaced it with one from a 70s ford van... the hey kids, free candy kind of van)
When you are getting the passive ventilation at fan position 0 you can try to push the recirculation button. When it lights up it should be recirculating and the 'flow thru' ventilation should stop. If this does not work, there is a problem in the vacuum system.
I earlier alluded to some problems I found in the vacuum system in my car. One is the bellows for the defroster flap was leaking air from one side. The other is the solenoid complex had cracked solder joints resulting in complete failure of the vacuum system.
If you remove the trim panel under the glovebox you should see the vacuum solenoids mounted on the airbox. On my car this was on the lower part of the box just by the center console. You will see a 1-row electrical connector on the left side and a row of vacuum tubes on the top of it. When I put my fingers on this in various places and it clicked, I knew I found a problem, took it out and remelted all the joints on the bottom of it, adding a small amount of solder to each one.
It is a bit easier to check the vacuum system for leaks, but the solenoid has to be working. With key on and ignition off, you should hear clicks from under the dash as you change the recirculation setting and move the ventilation selector to different positions. When my solenoid complex was acting up, I had no clicks.
Since you can see the recirculation flap (under the blower fan) and heater valve, you can use them to check the vacuum system for leaks. Basically if you know this component should have vacuum on it, and it is in the opposite position, this suggests a leak. To turn all vacuum solenoids off:
- Recirculation OFF
- A/C OFF (prevents recirculation from being active)
- temperature control at red dot (prevents heater valve closing)
- ventilation selector at DEFROST+FLOOR position
From this state, with motor running, you can check:
- heater valve, by moving the thermostat control to the red and blue dots.
- recirculation flap, by pushing the button. I can hear it in my car when it closes.
- Defrost shutter 1: ventilator in defrost position.
- Defrost shutter 2: ventilator in floor position.
Unfortunately the two face shutters are never activated independently.
- Small face shutter is active along with defrost shutter 2, check in face+floor position.
- Large face shutter is active along with defrost shutter 2 and small face shutter, check in face position.
If the heater valve opens when it should be closed, as you check the ventilation positions, this shows a one of those bellows has a leak.
Example: In my car, defrost shutter 2 was leaking (when this has vacuum, it moves to block the defroster.) So, I lost all vacuum except when set to DEFROST or DEFROST+FLOOR.
There are three vacuum ports on the firewall. Two are vacuum sources, and have check valves, the other one is the heater valve control. If you unhook the check valves from the firewall, and use your vacuum pump, one of the ports should hold vacuum when the controls are set as described above. The other port is for the temperature sensor, basically this is a metered vacuum leak to draw air into the sensor.
As long as the ignition is ON, the ECC should be controlling the heater valve and mix door. The goal for it is to get the temperature in the cabin moving towards the "thermostat setting." It will look at the cabin temp sensor and the sunlight sensor to try and figure out how warm the air should be. This happens at all times regardless of the fan setting, as long as the ignition is on.
To override this control system and control the heater valve and mix doors manually, set the thermostat control to the red dot (heater valve open) or the blue dot (heater valve closed.)
The normal/resting position for the heater valve is "open" or hot. The heater valve has a vacuum bellows in it (cylinder) and there is a protruding arm with a link to the actual valve lever. Observe it in the rest position. You should be able to put your finger on it and push the arm into the cylinder. When vacuum is applied to the cylinder, the arm will retract fully. When you get used to how it looks, you will be able to tell if it is open or closed by looking at the arm. Of course you can also test it with a vacuum pump if you like. (My valve leaked water so I replaced it with one from a 70s ford van... the hey kids, free candy kind of van)
When you are getting the passive ventilation at fan position 0 you can try to push the recirculation button. When it lights up it should be recirculating and the 'flow thru' ventilation should stop. If this does not work, there is a problem in the vacuum system.
I earlier alluded to some problems I found in the vacuum system in my car. One is the bellows for the defroster flap was leaking air from one side. The other is the solenoid complex had cracked solder joints resulting in complete failure of the vacuum system.
If you remove the trim panel under the glovebox you should see the vacuum solenoids mounted on the airbox. On my car this was on the lower part of the box just by the center console. You will see a 1-row electrical connector on the left side and a row of vacuum tubes on the top of it. When I put my fingers on this in various places and it clicked, I knew I found a problem, took it out and remelted all the joints on the bottom of it, adding a small amount of solder to each one.
It is a bit easier to check the vacuum system for leaks, but the solenoid has to be working. With key on and ignition off, you should hear clicks from under the dash as you change the recirculation setting and move the ventilation selector to different positions. When my solenoid complex was acting up, I had no clicks.
Since you can see the recirculation flap (under the blower fan) and heater valve, you can use them to check the vacuum system for leaks. Basically if you know this component should have vacuum on it, and it is in the opposite position, this suggests a leak. To turn all vacuum solenoids off:
- Recirculation OFF
- A/C OFF (prevents recirculation from being active)
- temperature control at red dot (prevents heater valve closing)
- ventilation selector at DEFROST+FLOOR position
From this state, with motor running, you can check:
- heater valve, by moving the thermostat control to the red and blue dots.
- recirculation flap, by pushing the button. I can hear it in my car when it closes.
- Defrost shutter 1: ventilator in defrost position.
- Defrost shutter 2: ventilator in floor position.
Unfortunately the two face shutters are never activated independently.
- Small face shutter is active along with defrost shutter 2, check in face+floor position.
- Large face shutter is active along with defrost shutter 2 and small face shutter, check in face position.
If the heater valve opens when it should be closed, as you check the ventilation positions, this shows a one of those bellows has a leak.
Example: In my car, defrost shutter 2 was leaking (when this has vacuum, it moves to block the defroster.) So, I lost all vacuum except when set to DEFROST or DEFROST+FLOOR.
There are three vacuum ports on the firewall. Two are vacuum sources, and have check valves, the other one is the heater valve control. If you unhook the check valves from the firewall, and use your vacuum pump, one of the ports should hold vacuum when the controls are set as described above. The other port is for the temperature sensor, basically this is a metered vacuum leak to draw air into the sensor.
Last edited by VDonkey; Apr 6, 2015 at 10:59 PM.
Thread Starter
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Junior Member
Joined: Jun 2014
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Pretty much what Nick says but this may help clarify.
As long as the ignition is ON, the ECC should be controlling the heater valve and mix door. The goal for it is to get the temperature in the cabin moving towards the "thermostat setting." It will look at the cabin temp sensor and the sunlight sensor to try and figure out how warm the air should be. This happens at all times regardless of the fan setting, as long as the ignition is on.
To override this control system and control the heater valve and mix doors manually, set the thermostat control to the red dot (heater valve open) or the blue dot (heater valve closed.)
The normal/resting position for the heater valve is "open" or hot. The heater valve has a vacuum bellows in it (cylinder) and there is a protruding arm with a link to the actual valve lever. Observe it in the rest position. You should be able to put your finger on it and push the arm into the cylinder. When vacuum is applied to the cylinder, the arm will retract fully. When you get used to how it looks, you will be able to tell if it is open or closed by looking at the arm. Of course you can also test it with a vacuum pump if you like. (My valve leaked water so I replaced it with one from a 70s ford van... the hey kids, free candy kind of van)
When you are getting the passive ventilation at fan position 0 you can try to push the recirculation button. When it lights up it should be recirculating and the 'flow thru' ventilation should stop. If this does not work, there is a problem in the vacuum system.
I earlier alluded to some problems I found in the vacuum system in my car. One is the bellows for the defroster flap was leaking air from one side. The other is the solenoid complex had cracked solder joints resulting in complete failure of the vacuum system.
If you remove the trim panel under the glovebox you should see the vacuum solenoids mounted on the airbox. On my car this was on the lower part of the box just by the center console. You will see a 1-row electrical connector on the left side and a row of vacuum tubes on the top of it. When I put my fingers on this in various places and it clicked, I knew I found a problem, took it out and remelted all the joints on the bottom of it, adding a small amount of solder to each one.
It is a bit easier to check the vacuum system for leaks, but the solenoid has to be working. With key on and ignition off, you should hear clicks from under the dash as you change the recirculation setting and move the ventilation selector to different positions. When my solenoid complex was acting up, I had no clicks.
Since you can see the recirculation flap (under the blower fan) and heater valve, you can use them to check the vacuum system for leaks. Basically if you know this component should have vacuum on it, and it is in the opposite position, this suggests a leak. To turn all vacuum solenoids off:
- Recirculation OFF
- A/C OFF (prevents recirculation from being active)
- temperature control at red dot (prevents heater valve closing)
- ventilation selector at DEFROST+FLOOR position
From this state, with motor running, you can check:
- heater valve, by moving the thermostat control to the red and blue dots.
- recirculation flap, by pushing the button. I can hear it in my car when it closes.
- Defrost shutter 1: ventilator in defrost position.
- Defrost shutter 2: ventilator in floor position.
Unfortunately the two face shutters are never activated independently.
- Small face shutter is active along with defrost shutter 2, check in face+floor position.
- Large face shutter is active along with defrost shutter 2 and small face shutter, check in face position.
If the heater valve opens when it should be closed, as you check the ventilation positions, this shows a one of those bellows has a leak.
Example: In my car, defrost shutter 2 was leaking (when this has vacuum, it moves to block the defroster.) So, I lost all vacuum except when set to DEFROST or DEFROST+FLOOR.
There are three vacuum ports on the firewall. Two are vacuum sources, and have check valves, the other one is the heater valve control. If you unhook the check valves from the firewall, and use your vacuum pump, one of the ports should hold vacuum when the controls are set as described above. The other port is for the temperature sensor, basically this is a metered vacuum leak to draw air into the sensor.
As long as the ignition is ON, the ECC should be controlling the heater valve and mix door. The goal for it is to get the temperature in the cabin moving towards the "thermostat setting." It will look at the cabin temp sensor and the sunlight sensor to try and figure out how warm the air should be. This happens at all times regardless of the fan setting, as long as the ignition is on.
To override this control system and control the heater valve and mix doors manually, set the thermostat control to the red dot (heater valve open) or the blue dot (heater valve closed.)
The normal/resting position for the heater valve is "open" or hot. The heater valve has a vacuum bellows in it (cylinder) and there is a protruding arm with a link to the actual valve lever. Observe it in the rest position. You should be able to put your finger on it and push the arm into the cylinder. When vacuum is applied to the cylinder, the arm will retract fully. When you get used to how it looks, you will be able to tell if it is open or closed by looking at the arm. Of course you can also test it with a vacuum pump if you like. (My valve leaked water so I replaced it with one from a 70s ford van... the hey kids, free candy kind of van)
When you are getting the passive ventilation at fan position 0 you can try to push the recirculation button. When it lights up it should be recirculating and the 'flow thru' ventilation should stop. If this does not work, there is a problem in the vacuum system.
I earlier alluded to some problems I found in the vacuum system in my car. One is the bellows for the defroster flap was leaking air from one side. The other is the solenoid complex had cracked solder joints resulting in complete failure of the vacuum system.
If you remove the trim panel under the glovebox you should see the vacuum solenoids mounted on the airbox. On my car this was on the lower part of the box just by the center console. You will see a 1-row electrical connector on the left side and a row of vacuum tubes on the top of it. When I put my fingers on this in various places and it clicked, I knew I found a problem, took it out and remelted all the joints on the bottom of it, adding a small amount of solder to each one.
It is a bit easier to check the vacuum system for leaks, but the solenoid has to be working. With key on and ignition off, you should hear clicks from under the dash as you change the recirculation setting and move the ventilation selector to different positions. When my solenoid complex was acting up, I had no clicks.
Since you can see the recirculation flap (under the blower fan) and heater valve, you can use them to check the vacuum system for leaks. Basically if you know this component should have vacuum on it, and it is in the opposite position, this suggests a leak. To turn all vacuum solenoids off:
- Recirculation OFF
- A/C OFF (prevents recirculation from being active)
- temperature control at red dot (prevents heater valve closing)
- ventilation selector at DEFROST+FLOOR position
From this state, with motor running, you can check:
- heater valve, by moving the thermostat control to the red and blue dots.
- recirculation flap, by pushing the button. I can hear it in my car when it closes.
- Defrost shutter 1: ventilator in defrost position.
- Defrost shutter 2: ventilator in floor position.
Unfortunately the two face shutters are never activated independently.
- Small face shutter is active along with defrost shutter 2, check in face+floor position.
- Large face shutter is active along with defrost shutter 2 and small face shutter, check in face position.
If the heater valve opens when it should be closed, as you check the ventilation positions, this shows a one of those bellows has a leak.
Example: In my car, defrost shutter 2 was leaking (when this has vacuum, it moves to block the defroster.) So, I lost all vacuum except when set to DEFROST or DEFROST+FLOOR.
There are three vacuum ports on the firewall. Two are vacuum sources, and have check valves, the other one is the heater valve control. If you unhook the check valves from the firewall, and use your vacuum pump, one of the ports should hold vacuum when the controls are set as described above. The other port is for the temperature sensor, basically this is a metered vacuum leak to draw air into the sensor.
wow, that's extremely detailed! Thanks!
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