1993 Heat/Defrost Issue
#1
1993 Heat/Defrost Issue
Not to long ago I bought a 1993 940. I am having issues with getting a strong current of air from any of the ducts. Whether floor, defrost, or dash, I seem to just be getting a radiating heat but not an actual air movement. If I were to take a piece of toilet paper and hold it to the vent I would get no movement at all, yet I can feel heat in the car.
So I have checked all the vacuum bellows for operation.. they work. I checked the servo motor for the heat control and the recirculation bellow. All good there. There are no vacuum leaks or issues with any of the diaphragms.
So here is my question. Since the vehicle is older could the filter after the evaporator be so clogged that there is entirely no air movement through the matrix. I have checked the blower motor and it works fine. I know that this is a significant amount of work to change this filter so I was wondering if anyone else has had or heard of an issue like this.
Also the water valve has been bypassed. Meaning there is not one on the vehicle. Plus it is manual control and not electronic.
Any help or advice would be greatly appreciated.
So I have checked all the vacuum bellows for operation.. they work. I checked the servo motor for the heat control and the recirculation bellow. All good there. There are no vacuum leaks or issues with any of the diaphragms.
So here is my question. Since the vehicle is older could the filter after the evaporator be so clogged that there is entirely no air movement through the matrix. I have checked the blower motor and it works fine. I know that this is a significant amount of work to change this filter so I was wondering if anyone else has had or heard of an issue like this.
Also the water valve has been bypassed. Meaning there is not one on the vehicle. Plus it is manual control and not electronic.
Any help or advice would be greatly appreciated.
#2
How can you have any temperature other than HOT without the water valve? How do you control the heat level? Are your VENTS operating? Are you able to change the AIRFLOW from the DEFROST (windshield) setting to the MIDDLE vents and to the FLOOR?
I have never heard of a filter after the evaporator; you may have the fan intake plugged by leaves which is the only thing that would reduce/stop airflow. Oh, and if you have MANUAL controls (sliders), this must be a non US version 940, right?
I have never heard of a filter after the evaporator; you may have the fan intake plugged by leaves which is the only thing that would reduce/stop airflow. Oh, and if you have MANUAL controls (sliders), this must be a non US version 940, right?
#3
How can you have any temperature other than HOT without the water valve? How do you control the heat level? Are your VENTS operating? Are you able to change the AIRFLOW from the DEFROST (windshield) setting to the MIDDLE vents and to the FLOOR?
I have never heard of a filter after the evaporator; you may have the fan intake plugged by leaves which is the only thing that would reduce/stop airflow. Oh, and if you have MANUAL controls (sliders), this must be a non US version 940, right?
I have never heard of a filter after the evaporator; you may have the fan intake plugged by leaves which is the only thing that would reduce/stop airflow. Oh, and if you have MANUAL controls (sliders), this must be a non US version 940, right?
It is a US version and there is indeed a filter after the evaporator. Why it is there is beyond me.
#5
OK, so what you are saying is that the fan runs at good speed, but you get no airflow out of ANY vents, no control with the *****? BTW, your system is electronic. I'd say that you have a bad CONTROL UNIT, the electronic control box with all the *****. It costs TOO MUCH new from Volvo, it's not available aftermarket BUT plentiful used on Ebay OR easily repairable. If you take it out and open it, usually a burned spot will be obvious on the circuit board--repair that, and all will be well.
(A plugged filter, if there was one, would rarely stop ALL FLOW.)
(A plugged filter, if there was one, would rarely stop ALL FLOW.)
#6
OK, so what you are saying is that the fan runs at good speed, but you get no airflow out of ANY vents, no control with the *****? BTW, your system is electronic. I'd say that you have a bad CONTROL UNIT, the electronic control box with all the *****. It costs TOO MUCH new from Volvo, it's not available aftermarket BUT plentiful used on Ebay OR easily repairable. If you take it out and open it, usually a burned spot will be obvious on the circuit board--repair that, and all will be well.
(A plugged filter, if there was one, would rarely stop ALL FLOW.)
(A plugged filter, if there was one, would rarely stop ALL FLOW.)
I appreciate your response lev.
Here is a decent diagram of the routing and controls.
Heater unit With atc (auto. Temp. Control) combu 940. Combu. Fits: Volvo | VolvoPartsWebstore.com
#8
Good job, you are certainly on it!
Hm, well, something is preventing the air from coming out of the housing and going to the vents... Must be a gate stuck shut somewhere, that's all I can think of at this point. The filter, I see there is one, has never been an issue before... Keep posting, this is interesting.
Hm, well, something is preventing the air from coming out of the housing and going to the vents... Must be a gate stuck shut somewhere, that's all I can think of at this point. The filter, I see there is one, has never been an issue before... Keep posting, this is interesting.
#9
the non-ECC controller used on US model 740/940's is vacuum activated, not electronic. only the ECC (Electronic Climate Control) that has degrees on the temp **** is electronic.
vacuum comes from the intake manifold, goes through a 1-way valve, to a storage bottle tucked deep under the dash somewhere, to the vent control box. various vacuum lines come out of the vent controller and go to the flap actuators. no flaps at all probably means no vacuum there, check the main vacuum hose.
even with all the flaps in the neutral position, most of the air should be coming out of the main dashboard vents when the fan is on.
there's 3 sets of flaps. 1) redirects air to the defroster vents on top of the dashboard. 2) redirects air to the heater vents in the foot wells. and 3) closes the outside air so the car recirculates inside air. if both 1 and 2 are 'off', then the air comes out of the aimable dashboard vents (which have their own manual control to open/close). flap 3 is controlled by the recirculate button, and selects where the fan sucks the intake air from.
the fan blows the air past the AC condensor, then past the heater core, then up to the manifold where these various flaps are.
if your fan is working, the air has to be going SOMEwhere. AFAIK, no 740/940 has a cabin air filter.
vacuum comes from the intake manifold, goes through a 1-way valve, to a storage bottle tucked deep under the dash somewhere, to the vent control box. various vacuum lines come out of the vent controller and go to the flap actuators. no flaps at all probably means no vacuum there, check the main vacuum hose.
even with all the flaps in the neutral position, most of the air should be coming out of the main dashboard vents when the fan is on.
there's 3 sets of flaps. 1) redirects air to the defroster vents on top of the dashboard. 2) redirects air to the heater vents in the foot wells. and 3) closes the outside air so the car recirculates inside air. if both 1 and 2 are 'off', then the air comes out of the aimable dashboard vents (which have their own manual control to open/close). flap 3 is controlled by the recirculate button, and selects where the fan sucks the intake air from.
the fan blows the air past the AC condensor, then past the heater core, then up to the manifold where these various flaps are.
if your fan is working, the air has to be going SOMEwhere. AFAIK, no 740/940 has a cabin air filter.
#10
So I'm back at it again today. I have been doing some poking around and talking to some people and want to bounce something off you guys. Someone said that I may have switched polarity on the blower motor causing the blower to spin in the incorrect direction. I grabbed some toilet paper and directed it to the intake to see if it would suck in. I have to be honest that it was difficult to tell whether it was blowing or sucking. Also I looked at some of the wiring to the motor it self and found two butt splices connecting the wires from the harness to the motor. I doubt that this is factory but then again it could be. My question based on the fact that I haven't taken the time to figure out the exact wire routing for the ballast resistor, is if I went ahead and switched polarity to the motor would I cause damage to the system if this guess is incorrect.
Any help or previous knowledge of this would come in handy.
Thanks in advance.
Any help or previous knowledge of this would come in handy.
Thanks in advance.
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seeofgreen
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02-11-2021 07:03 PM