Heat...and then No heat...then Heat?

Not sure what the problem is,but the heat will work and then it gets cool. I mess with the dial and the heat come back. I figure it's the air mix servo that opens/closes the flap depending on which temp the dial is on. I replaced that part and it still does it.

Any ideas as to what else it might be?

 

Yeah I was having an issue with the same thing I was thinking the servo motor too, but wasn't my issue.

After doing a search maybe this is our issue? Check out this thread : https://www.tacomaworld.com/threads...climate-control-problem.413357/#post-11743291

 

Maybe. Where is the control unit?

 

Check your coolant level.

 

I will.

 

Probably Fried harness and plug at the heater motor. Crawl under and look at where the heater motor under the passenger side dash plugs in. Same issue here. I found the plastic all melted. Not sure what the fix is aside from a new harness and motor

 

Ill check.

 

Coolant was ok.

 

Ive not had time to check things for a while, but I did notice today that with the air on High, I hear a slight whistle and then there is no heat. If I keep turning the air on and off until I don't hear that whistle, then the heat works. Is this anything or just a coincidence?

 

Can you move the door manually to hot and cold with the actuator removed.

 

I haven't tried, but I will tomorrow. What would it be if it did or did not open? Could the door not be opening all the way?

 

If the door is binding it's either broken, something fell down the vents and got stuck in it, or the HVAC housing it sits in is warped. I believe there is also a heater control valve on one of the heater hoses, you need to check that for proper operation too.

 

Finally got under the dash and checked wires,plugs,etc and found nothing that looked like it wasn't working correctly,UNTIL I decided to remove the cable that moves the mechanism that the servo goes to,that also runs to the valve under the hood.

After I unhooked both ends and tried to pull on the cable,there was alot of resistance. I sprayed some teflon on the cable and let it run down the plastic tube the cable was in and it began moving smoothly. I then hooked things back up and the Heat was back and it was way hotter than usual. Maybe the resistance wasn't allowing the cable to engage either way enough. I'm not sure if this is actually the issue or not,but as of now,the truck has been running for around 4 hrs and the heat is still working. I'll give it a week or two to see what happens an update the outcome. Thanks for all the info.

 

Well,things were fine for a few weeks and then the issue come back. Not sure what else to check.

 

heat. no heat. heat.

Sounds like my wife is in control of the thermostat.

 

Blend door actuator

 

I already replaced the one underneath on passengers side. Is that the one you're talking about?

 

It's above the HVAC box in middle

 

Ok.Ill check it when I get a chance.