More Blower Issues. Engine hot. Blower barely working. Engine cold, blower full spe

[87stars_stripes]

Engine hot. Blower barely working and putting out minimal heat. ????
Engine cold not running = Blower full speed on defrosters. ????
Max Blower Speed/Hot/Vent Selected.

I am getting full blower speed at the defrosters when the engine is up to temp and running. Why is this? Yesterday I was driving at full temperature I could barely get a breeze of air from the vents or the defroster. With the engine off and cold, the blower motor blows full speed, but only comes out the defrost.

I thought this was low vacuum related if the problem occurred when the engine is running, but it's doing it even with the engine off, so is low vacuum still supposed to be a factor? The system should be designed to operate with no vacuum if the engine is off correct?


Cabin Air temp Sensor- Could this cause the blower to blow out the defrosters while on vent setting?
Blender Door- I don't know much about the blender door.
Low Vacuum- Why would low vacuum cause eratic issues such as blowing from the defroster on vent setting even when the car is not running? Vacuum should not be expected.
Thermal Blower Lockout- This is the switch that runs inline with the heater pipes. I have it disconnected and both vacuum feeds plugged up/

[sly]

Check the contacts on the blower lockout as well as the blower harness. If there is any melty plastic on any of that, the wires are getting hot due to low voltage, high current from bad contacts.

[87stars_stripes]

If the thermal blower lockout switch is the same thing as the auto temp control sensor that runs in line with the heater hose, I have that eliminated. I will check the wiring though. It seems to be blowing full blast again. I can't win. Thanks though.

[gadget73]

if the air temp sensor is flaky and you happen to have the fan speed set to auto, it'll slow down if it moves the blend door towards the middle of it's range. This also makes for crappy heat. If the blower speed is not set to auto, the blend door position will have nothing to do with how much air comes through but it might be related to poor heat output. Pulling the hose off the blend door will force it to full hot. If it gets hot with the vac line unhooked, the sensor is no good.

With no vacuum, the system should give you hot defrost only. If the blower is audibly running at full crank but you aren't getting much air, I'd suspect either the wheel on the blower is packed up with crap or the air doors in the dash have failed in such a way that its mostly blocking things. Another possible if you've had the heater core or plenum assembly out is the bolts are loose and there is a big gap between the plenum and the ductwork, or maybe the foam seal is completely gone. If you open the glovebox, does it have a nice breeze blowing out from behind the dash? If so, look for sealing problems.

[87stars_stripes]

Thanks for chiming in Gadget. Good info. As of yesterday after the post, it seems to be blowing full blast and coming in hot as well. If I have anymore problems I will definitely refer back to that info though. Maybe it was low engine vacuum related? Could running slightly cool due to a big radiator and highway cruising speeds cause lower coolant temps and seemingly less air volume from the vents? BTW, today i had the blower on full speed with the temp set to full cold, and it was blowing the hardest I've ever felt it. Does that mean anything?

if the air temp sensor is flaky and you happen to have the fan speed set to auto, it'll slow down if it moves the blend door towards the middle of it's range. This also makes for crappy heat. If the blower speed is not set to auto, the blend door position will have nothing to do with how much air comes through but it might be related to poor heat output. Pulling the hose off the blend door will force it to full hot. If it gets hot with the vac line unhooked, the sensor is no good.

With no vacuum, the system should give you hot defrost only. If the blower is audibly running at full crank but you aren't getting much air, I'd suspect either the wheel on the blower is packed up with crap or the air doors in the dash have failed in such a way that its mostly blocking things. Another possible if you've had the heater core or plenum assembly out is the bolts are loose and there is a big gap between the plenum and the ductwork, or maybe the foam seal is completely gone. If you open the glovebox, does it have a nice breeze blowing out from behind the dash? If so, look for sealing problems.

[gadget73]

doubtful. It honestly sounds more like some sort of electrical fault to me than anything temperature related. maybe an air door broken off the hinge that flops out of the way and makes things work better, but a crapped up connection at the blower resistor or at the blower fan plug itself sounds a little more likely to me. If you have the TBL and its giving you trouble in floor mode, that dying could also be part of the issue.

[87stars_stripes]

No TBL anymore, but I was looking for the blower motor resistor and I couldn't identify it. What's it look like?

doubtful. It honestly sounds more like some sort of electrical fault to me than anything temperature related. maybe an air door broken off the hinge that flops out of the way and makes things work better, but a crapped up connection at the blower resistor or at the blower fan plug itself sounds a little more likely to me. If you have the TBL and its giving you trouble in floor mode, that dying could also be part of the issue.

[gadget73]

Its behind the passenger side valve cover. Find the bundle of wires that goes to a plug on the firewall and thats it. The connector tends to get craptastic. Its not in use at less than full speed, but I don't know off the top of my head where the ground for high speed operation comes from. if it happens to pass through that plug, it'll give you trouble.