Low air flow from heater fan
10-16-2015, 08:21 AM
#16
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i have a similar problem with air flow. all actuators work as i cycle through the positions.
if i remove the blower motor resistor the air flow will knock you over. i found out the blend door regulator wasn't working so i removed it and operated it manually. no change. it seems as though no air gets past the evaporator. previous owner said that he had the evaporator and blower motor replaced. guy told him he knocked off a vent when he did it. that doesn't make sense to me. i am new to this and have the dash tore out and access to the evap box. is there another door other than blend inside it? by the way 2000 cherokee sport
if i remove the blower motor resistor the air flow will knock you over. i found out the blend door regulator wasn't working so i removed it and operated it manually. no change. it seems as though no air gets past the evaporator. previous owner said that he had the evaporator and blower motor replaced. guy told him he knocked off a vent when he did it. that doesn't make sense to me. i am new to this and have the dash tore out and access to the evap box. is there another door other than blend inside it? by the way 2000 cherokee sport
10-16-2015, 10:55 AM
#17
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Year: 1999
Model: Cherokee
Engine: 4.0
i have a similar problem with air flow. all actuators work as i cycle through the positions.
if i remove the blower motor resistor the air flow will knock you over. i found out the blend door regulator wasn't working so i removed it and operated it manually. no change. it seems as though no air gets past the evaporator. previous owner said that he had the evaporator and blower motor replaced. guy told him he knocked off a vent when he did it. that doesn't make sense to me. i am new to this and have the dash tore out and access to the evap box. is there another door other than blend inside it? by the way 2000 cherokee sport
if i remove the blower motor resistor the air flow will knock you over. i found out the blend door regulator wasn't working so i removed it and operated it manually. no change. it seems as though no air gets past the evaporator. previous owner said that he had the evaporator and blower motor replaced. guy told him he knocked off a vent when he did it. that doesn't make sense to me. i am new to this and have the dash tore out and access to the evap box. is there another door other than blend inside it? by the way 2000 cherokee sport
Well if the blend-air door actuator is not working what's the mystery?
10-16-2015, 12:24 PM
#19
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the problem is, that i removed the regulator and was able to move the blend door by hand. there was no change in the air flow. is there any other door inside the evaporator? with the blower motor resistor removed, i can see the evaporator, if i look from the other side i can see the heater core. i don't want to tear out the whole assembly if there is any way to avoid it.
10-16-2015, 07:26 PM
#21
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heat works, air works, just very little air flow. i am unsure since i haven't pulled the heater box yet. i am new to this so my understanding is limited. i thought that the blend door was to control the mixture of hot and cold air that was pushed through the vents. to me, it would seem that the blend door is the only thing separating the to sides, hot and cold. if i am able to put a light into one side or the other, i should be able to see that light if the blend door is somewhere in the middle. i get no air past the a/c side.
10-17-2015, 07:21 AM
#22
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Year: 1999
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heat works, air works, just very little air flow. i am unsure since i haven't pulled the heater box yet. i am new to this so my understanding is limited. i thought that the blend door was to control the mixture of hot and cold air that was pushed through the vents. to me, it would seem that the blend door is the only thing separating the to sides, hot and cold. if i am able to put a light into one side or the other, i should be able to see that light if the blend door is somewhere in the middle. i get no air past the a/c side.
Is that very little airflow from any outlet?
Does the blower fan speed change with any of the four settings selected?
Does the airflow change when MAX AIR (recirculation) is selected on the mode selector?
The Blend-Air Door is the device to 'blend' cold and hot air. All other doors in the HVAC Unit divert the air to the selected outlets.
Some pics of inside the HVAC Unit - Bottom half:
10-17-2015, 09:28 AM
#23
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thank you for the pics. fan works all speeds. i have the dash out and can see all vent doors working. i move the blend door manually and no change in air flow. recirc door works as well. i must have blockage. i am going to buy an inspection camera and see whats going on. it will be worth the investment if i don't need to tear out the hvac box. thank you. i will post with the results.
10-17-2015, 09:48 AM
#24
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thank you for the pics. fan works all speeds. i have the dash out and can see all vent doors working. i move the blend door manually and no change in air flow. recirc door works as well. i must have blockage. i am going to buy an inspection camera and see whats going on. it will be worth the investment if i don't need to tear out the hvac box. thank you. i will post with the results.
You can remove the blower resistor block and see if you see crap in the blower chamber (nesting materials from critters).
If so. you may be able to suck some of it out using a shop vac. otherwise you'd have to remove the blower to remove it.
With the Recirc air door open you can also see the blower fan. With the fan off, reach in with a screwdriver and gently touch the fan and see if it is secure. Also, see if it turns freely.
With the Recirc door open, key to RUN/ON, turn the fan speed to 1 and see if the fan is turning.
10-17-2015, 01:24 PM
#25
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got my scope and couldn't see anything. so i hooked everything back and nothing. fan wouldn't spin. i got to checking the wiring, when they replaced blower motor they wired it backwards. i am a genius for not realizing which way the motor was turning. but now i am troubleshooting the whole circuit. i am only getting 4 volts to the motor. when i hooked it up to a 12 volt source it spun like crazy. my guess is the resistor went bad after all of my in and outs. thanks for all the pics and diagrams. i am sure i will have it rolling soon.
10-18-2015, 06:57 PM
#26
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FINALLY! got to moving stuff around and everything works. i don't understand, probably should care, but, i got it all put back together and it works. the only real issue was the blower was reversed. i felt air through the resistor hole and thought it was okay. learned a lot and truly appreciated the support. now for the tcm code i got...
10-19-2015, 05:55 AM
#28
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1698, cel was on when i got everything back together. i looked it up, said no communication between ecm and tcm. also saw one that said the battery was disconnected too long. hoping the latter but, that doesn't makes sense to me. haven't had time to do anything else.
12-02-2015, 06:02 PM
#29
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I finally got around to (or more accurately, decided to pay for) figuring out the problem on my '01. As a reminder, I had good airflow with the blend door in the cold position, but the flow dropped off as the door was moved to hot.
The solution started as CCKen said to golftoad. Taking out the blower resister block showed a mouse house on the evap coil. After removing the heater box we could see that the evap coil was about half obstructed. But that would reduce air flow at any temp setting, so that couldn't be it (although it certainly needed to be cleaned out).
There was a little bit of debris (that had snuck past the evap coil) on the air inlet side of the heater core, but not enough to make a difference. But holding the core up to the light you realized that you couldn't see light through it! A bunch of fine debris had come past the evap coil and worked its way deep into the heater core fins. I decided to replace the heater core and the (leaking) evap coil with new while everything was apart. Now there's good air flow at any temp setting!
Just thought I'd close this out for anyone who stumbles on it later.
The solution started as CCKen said to golftoad. Taking out the blower resister block showed a mouse house on the evap coil. After removing the heater box we could see that the evap coil was about half obstructed. But that would reduce air flow at any temp setting, so that couldn't be it (although it certainly needed to be cleaned out).
There was a little bit of debris (that had snuck past the evap coil) on the air inlet side of the heater core, but not enough to make a difference. But holding the core up to the light you realized that you couldn't see light through it! A bunch of fine debris had come past the evap coil and worked its way deep into the heater core fins. I decided to replace the heater core and the (leaking) evap coil with new while everything was apart. Now there's good air flow at any temp setting!
Just thought I'd close this out for anyone who stumbles on it later.
12-02-2015, 06:32 PM
#30
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Join Date: Aug 2010
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Year: 1999
Model: Cherokee
Engine: 4.0
I finally got around to (or more accurately, decided to pay for) figuring out the problem on my '01. As a reminder, I had good airflow with the blend door in the cold position, but the flow dropped off as the door was moved to hot.
The solution started as CCKen said to golftoad. Taking out the blower resister block showed a mouse house on the evap coil. After removing the heater box we could see that the evap coil was about half obstructed. But that would reduce air flow at any temp setting, so that couldn't be it (although it certainly needed to be cleaned out).
There was a little bit of debris (that had snuck past the evap coil) on the air inlet side of the heater core, but not enough to make a difference. But holding the core up to the light you realized that you couldn't see light through it! A bunch of fine debris had come past the evap coil and worked its way deep into the heater core fins. I decided to replace the heater core and the (leaking) evap coil with new while everything was apart. Now there's good air flow at any temp setting!
Just thought I'd close this out for anyone who stumbles on it later.
The solution started as CCKen said to golftoad. Taking out the blower resister block showed a mouse house on the evap coil. After removing the heater box we could see that the evap coil was about half obstructed. But that would reduce air flow at any temp setting, so that couldn't be it (although it certainly needed to be cleaned out).
There was a little bit of debris (that had snuck past the evap coil) on the air inlet side of the heater core, but not enough to make a difference. But holding the core up to the light you realized that you couldn't see light through it! A bunch of fine debris had come past the evap coil and worked its way deep into the heater core fins. I decided to replace the heater core and the (leaking) evap coil with new while everything was apart. Now there's good air flow at any temp setting!
Just thought I'd close this out for anyone who stumbles on it later.
