Fan not blowing hot air

[p00flakes]

Hi All,

Noticed that despite turning the heater controls all the way up, the air blown out of the vents is still cold/room temperature. Engine temperature was normal as far as I could tell (between H and C). I've tried doing a search, but could not find any specific thread that mentions this situation. I'm planning on checking the coolant levels first, but am looking for any other ideas/things to check? Broken thermostat? It's a 2006 SE with 36k miles. Thanks in advance!

 

[p00flakes]

ok, I've verified the following things:
1) checked coolant. Appears to be adequate (about 1 inch below the F mark)
2) the two aluminum colored tubes going into the firewall were hot to the touch
3) unplugged the battery for a couple of minutes and reconnected it (perhaps resetting the climate control). still cold air.
4) all vents are blowing cold air- no difference in air temperature between vents

Based on my readings, it appears to be either:
1) thermostat stuck open/closed
2) blend door not working

Does anyone know how to check/verify if the thermostat or blend door are malfunctioning before I buy a replacement? The engine is not running hot/overheating, so that may mean the thermostat is working ok? Is it possible that the fuse to the blend door is blown?

Any thoughts/things to try would be greatly appreciated. Thanks guys and gals!

P.

Hi All,

Noticed that despite turning the heater controls all the way up, the air blown out of the vents is still cold/room temperature. Engine temperature was normal as far as I could tell (between H and C). I've tried doing a search, but could not find any specific thread that mentions this situation. I'm planning on checking the coolant levels first, but am looking for any other ideas/things to check? Broken thermostat? It's a 2006 SE with 36k miles. Thanks in advance!

 

[AuSeeker]

It is not your thermostat, if the themostat was stuck open the engine would still heat up eventually, if stuck closed the engine would overheat, and since the tubes going through the firewall to the heater core are getting hot means the coolant is going through the heater core, so the issue is elsewhere.

The problem is most likely with the blend door, why the blend door isn't working is what needs to be determined, it could be a fuse but if the HVAC controls are all working otherwise I doubt it's a fuse, the blend door acutator/servo is my best guess since it's a common issue and usually is accompanied by a clicking sound behind the glovebox where the blend doors are located, the clicking is caused by the actuator's plastic gear slipping where it connects to the blend door's arm, there 3 blend doors (temperature, vent selection, and recirculating air flow) and each has it's own actuator/servo, there's a lower one and another higher up (not sure of the location of the 3rd one), the lower one it is said is the temperature blend door, but you should be able to determine which is the correct one simply by watching the actuator/s while changing the temperature settings and see which one is trying to move, the temperature blend door moves to direct the air either through the AC evaporator or the heater core or somewhere in between depending on the control settings.

If you are not getting anything trying to move on the actuators when changing temperature settings then you are having an issue with the control panel itself.

Here's a link a topic concerning the blends doors and a similar issue as your's, read it all but pay close attention to all the posts by [MENTION=85386]ghs215[/MENTION], he describes how to get to the actuators and remove them and replace them, it's not easy to get at them but can be done with his advice and a little patiences.

http://www.toyota-4runner.org/4th-gen-t4rs/260967-blend-door-actuator.html

If you find that both blend doors seem to be operating/moving correctly you make have an issue with debri getting in passed the cabin air filter (also located behind the glovebox) and clogging/blocking things up, even if the actuator is the cause of your issues I would recommend replacing the cabin air filter if it hasn't been replaced, should be done one a year at the very least or more often if you drive in very dusty conditions.

 

[ghs215]

It's a 2006 SE with 36k miles.

:hat: only 36k miles!?!?!?! May I suggest you break that thing in already, lol
[MENTION=205118]p00flakes[/MENTION] read my post, let us know if you have any other questions
[MENTION=149207]AuSeeker[/MENTION] Thank's for pointing [MENTION=205118]p00flakes[/MENTION] to the posts

 

[p00flakes]

Hi Auseeker!

Thanks so much for the detailed response. I actually ran the diagnostic check on the climate control unit as detailed in the service manual, and it pulled a code of 41:

41 Air Mix Damper Control
Servo Motor Circuit
(Passenger Side)
1. Damper servo subassembly
(Air mix damper
control servo motor)
2. Harness or connector
between damper servo
sub-assembly (air mix
damper control servo
motor) and A/C amplifier
3. A/C amplifier

so i'm pretty sure that the issue is with the temperature blend door. I removed the glove box, and took a look at the plastic pieces next to each of the servos. The top servo worked fine when I changed the air/mix on the climate control (defrost, face only, face and feet etc). But when I tried to change the temperature, nothing moved. It is possible that I didn't see the actuator on the temp blend door move, or the servo gear is stripped... I guess the next step would be to actually remove the temp blend door, keep it plugged in, and see if the servo actually moves... I really hope that I won't have to replace the entire climate control unit/ control panel. Regardless, at least i know it isn't the thermostat.:juggle:

It is not your thermostat, if the themostat was stuck open the engine would still heat up eventually, if stuck closed the engine would overheat, and since the tubes going through the firewall to the heater core are getting hot means the coolant is going through the heater core, so the issue is elsewhere.

The problem is most likely with the blend door, why the blend door isn't working is what needs to be determined, it could be a fuse but if the HVAC controls are all working otherwise I doubt it's a fuse, the blend door acutator/servo is my best guess since it's a common issue and usually is accompanied by a clicking sound behind the glovebox where the blend doors are located, the clicking is caused by the actuator's plastic gear slipping where it connects to the blend door's arm, there 3 blend doors (temperature, vent selection, and recirculating air flow) and each has it's own actuator/servo, there's a lower one and another higher up (not sure of the location of the 3rd one), the lower one it is said is the temperature blend door, but you should be able to determine which is the correct one simply by watching the actuator/s while changing the temperature settings and see which one is trying to move, the temperature blend door moves to direct the air either through the AC evaporator or the heater core or somewhere in between depending on the control settings.

If you are not getting anything trying to move on the actuators when changing temperature settings then you are having an issue with the control panel itself.

Here's a link a topic concerning the blends doors and a similar issue as your's, read it all but pay close attention to all the posts by [MENTION=85386]ghs215[/MENTION], he describes how to get to the actuators and remove them and replace them, it's not easy to get at them but can be done with his advice and a little patiences.

http://www.toyota-4runner.org/4th-gen-t4rs/260967-blend-door-actuator.html

If you find that both blend doors seem to be operating/moving correctly you make have an issue with debri getting in passed the cabin air filter (also located behind the glovebox) and clogging/blocking things up, even if the actuator is the cause of your issues I would recommend replacing the cabin air filter if it hasn't been replaced, should be done one a year at the very least or more often if you drive in very dusty conditions.

 

[p00flakes]

Haha, right? I managed to put about 6k miles on the runner in the last 8 months, so it's slowly creeping up there This will likely be my forever car :bravo:

:hat: only 36k miles!?!?!?! May I suggest you break that thing in already, lol

[MENTION=205118]p00flakes[/MENTION] read my post, let us know if you have any other questions

[MENTION=149207]AuSeeker[/MENTION] Thank's for pointing [MENTION=205118]p00flakes[/MENTION] to the posts

 

[AuSeeker]

Hi Auseeker!

Thanks so much for the detailed response. I actually ran the diagnostic check on the climate control unit as detailed in the service manual, and it pulled a code of 41:

41 Air Mix Damper Control
Servo Motor Circuit
(Passenger Side)
1. Damper servo subassembly
(Air mix damper
control servo motor)
2. Harness or connector
between damper servo
sub-assembly (air mix
damper control servo
motor) and A/C amplifier
3. A/C amplifier

so i'm pretty sure that the issue is with the temperature blend door. I removed the glove box, and took a look at the plastic pieces next to each of the servos. The top servo worked fine when I changed the air/mix on the climate control (defrost, face only, face and feet etc). But when I tried to change the temperature, nothing moved. It is possible that I didn't see the actuator on the temp blend door move, or the servo gear is stripped... I guess the next step would be to actually remove the temp blend door, keep it plugged in, and see if the servo actually moves... I really hope that I won't have to replace the entire climate control unit/ control panel. Regardless, at least i know it isn't the thermostat.:juggle:

You don't want to remove the blend door, only the acuator/servo, but I would first use a multi-meter or test light to see if you're getting power to the acuator wiring, if you are getting power to it then the contacts within the acutator are most likely burned out causing it not to turn the gear.

If you're not getting power to the wiring then you may have other issues to seek out/trouble shoot.

If you have power to the wiring and you remove the acuator I have seen where another member took his apart and seen where the contacts were burned.

 

[ghs215]

stick a flat blade screwdriver into the servo and turn it. See if the air blows :zoom:

 

[p00flakes]

Good point. Yeah now i'll have to search for the wiring diagram to the actuator to see which ones are power etc. Fun! :sad:

What I'm thinking is that if the contacts are actually burned out, then there may be something causing an overload or resistance to the servo's operation. I'm also going to check if the servo's plastic arm is worn out- if the attachment hole on the plastic arm (where the metal arm sticks into) has too much play, it could cause the mechanism to operate at a weird angle- causing unintended resistance... Too much theorizing at this point. Will have to investigate and report back!

You don't want to remove the blend door, only the acuator/servo, but I would first use a multi-meter or test light to see if you're getting power to the acuator wiring, if you are getting power to it then the contacts within the acutator are most likely burned out causing it not to turn the gear.

If you're not getting power to the wiring then you may have other issues to seek out/trouble shoot.

If you have power to the wiring and you remove the acuator I have seen where another member took his apart and seen where the contacts were burned.

 

[p00flakes]

I'm pretty sure that if I operate the servo manually, the entire mechanism will work- after all it is just opening and closing a door...

stick a flat blade screwdriver into the servo and turn it. See if the air blows :zoom:

 

[firebirdguy]

following

 

[p00flakes]

Hi All,

Just wanted to update you on the progress of this issue. I didn't have a chance to take a look at this issue until last night (days are getting colder, so it was a good reminder to fix it asap).

I tested the power to the harness, and got almost 5v, no problem there. I checked the fuse to the AC system (#12 in the engine compartment), no problem there. I thus decided that it was most likely the servo simply got burned out/failed due to age. I started removing the 3 screws on the aluminum frame that held the servo in place, and for some reason decided to try the blend door function again (by turning up and down the heat). And to my surprise, the servo began working again!!

I think what happened is that the mechanism got "stuck" in one position. It so happens that in the coldest position, the actuator/servo arm is in a particularly poor position for leverage. Loosening the screws that held the servo in place allowed the mechanism to get "unstuck". I had read other owners having an issue with the servo arm getting "knocked off" the guide rails connected to the blend doors, but this was not my specific issue.

So all in all, this trouble was likely due to a couple of factors:
1) Less than ideal positioning of the servo arm in the LO position (I run this position 90% of the time). As soon as the temp indicator goes higher then LO, the servo arm moves into a much more favorable position for leverage.
2) Poor lubrication of the guide path that the servo arm runs in when operating (the grease dries up over time)
3) Plastic wear in the actuator guide path due to always running the temp close to or at LO

If this issue happens again, I'll probably add some grease to the guide path, and avoid running in the LO position. Hope this helps anyone else that had this specific issue. And a big THANK YOU to AuSeeker and ghs215 for their input- it helped tremendously in the troubleshooting process!

p00flakes

 

[Powder_Hound]

Sadly, your heater core might be clogged. I wouldn’t think so with the low mileage, but it is possible. If all other tests are good I would consider this. I tried to flush my heater core to fix the issue, but it didn’t work. Ultimately, I replaced my heater core and voila, heat again.

I hope this isn’t the case as it’s an expensive repair as the entire dash has to come out to replace.