No heat in my truck

[MN4runnerman]

Specs to get them out of the way.
1999 3.4L 197xxx miles
-I’ve done a full coolant flush(back in July) part of scheduled maintenance and it was also done when it was purchased
-I’ve replaced the heater control valve and inspected the old one which was working properly(yay now I have a spare!).
-I’ve bypassed the rear heater due to the lines leaking and no one really sits back there
-I haven’t been able to get the heat to work since I bought the truck ~3 years ago and everything above has been done since
-It did sit for extended periods of time before I bought it. The PO told me.
So I have no heat in my truck. The last couple years I didn’t care to fix it because I would store it in the winter. Well this year I’m not so I’d like to get it working and I haven’t been able to figure it out. The temperature knob turns the control valve properly, AC works, blower works. Any ideas or where to go next? It’s getting cold out and it sucks. Thanks guys.

Edit: The blend door(which turned out to be the issue in my case) is located behind the ash try and underneath the radio on the bottom(basically the floor) of the center dashboard. There is no disassembly it is just past the plastic trim in the footwell.

 

[alumarine]

When you open the control valve does both the inlet and outlet get hot?

 

[Buckaroo]

Replace thermostat.

Buckaroo

 

[MN4runnerman]

When you open the control valve does both the inlet and outlet get hot?

Yes it does

Replace thermostat.

Buckaroo

Reasoning?(I should’ve mentioned that in the OP) It’s was replaced last winter when I did a crap ton of work to it. It didn’t work with the old thermostat in it which was a cheap replacement and the new one is an Aisin brand.

 

[JayRolla]

Disconnect heater core lines and see if water flows with a garden hose. Could be clogged.

 

[MN4runnerman]

Disconnect heater core lines and see if water flows with a garden hose. Could be clogged.

That’s what I’m thinking cuz it’s like the only thing left.

 

[4Reak Show]

Don't over look blend door cable. Knob turns two cables I believe. One for valve in engine bay, one for blend door. I'm not 100% on where it goes but you should be able to see something looking under the dash. Next time there's a 3rd Gen in my shop I'll take a peek if someone here doesn't beat me to it. My 2nd gens cable is right under the glove box. If it doesn't move with the knob pull cable off of tab if it's accessible and manual swing the door and see if you get heat. I've seen cables break and come off of their guide on other vehicles

 

[MN4runnerman]

Don't over look blend door cable. Knob turns two cables I believe. One for valve in engine bay, one for blend door. I'm not 100% on where it goes but you should be able to see something looking under the dash. Next time there's a 3rd Gen in my shop I'll take a peek if someone here doesn't beat me to it. My 2nd gens cable is right under the glove box. If it doesn't move with the knob pull cable off of tab if it's accessible and manual swing the door and see if you get heat. I've seen cables break and come off of their guide on other vehicles

I didn’t realize that there were 2 cables. I’ll take the glove box out tomorrow morning and take a look around tomorrow. Thanks for that idea

 

[4Reak Show]

I didn’t realize that there were 2 cables. I’ll take the glove box out tomorrow morning and take a look around tomorrow. Thanks for that idea

Well there's SOMETHING that moves the blend door. I'm not sure if yours is basic and cable operated or if you have the fancy unit and it has a little motor to move the door. Either way, that's an area to check. I'm curious what you find. I think my uncles old ass Toyota pickup had the cable installed wrong or popped off and after he reattached he said "it's so hot in my truck I could throw up" so it worked for him haha

 

[JayRolla]

Well there's SOMETHING that moves the blend door. I'm not sure if yours is basic and cable operated or if you have the fancy unit and it has a little motor to move the door. Either way, that's an area to check. I'm curious what you find. I think my uncles old ass Toyota pickup had the cable installed wrong or popped off and after he reattached he said "it's so hot in my truck I could throw up" so it worked for him haha

I'm also guessing blend door motor. It's a small actuator.

 

[MN4runnerman]

Well there's SOMETHING that moves the blend door. I'm not sure if yours is basic and cable operated or if you have the fancy unit and it has a little motor to move the door. Either way, that's an area to check. I'm curious what you find. I think my uncles old ass Toyota pickup had the cable installed wrong or popped off and after he reattached he said "it's so hot in my truck I could throw up" so it worked for him haha

It’s not a limited so I don’t think it’s computer controlled with a motor. I’ll find out. If it is a motor I’m gonna see if I can retrofit it and use a manual cable.

 

[etc.]

I flushed my heater core for probably 30 minutes in both directions and it still clogged within the first 500 miles.

I plumbed it to reverse the flow through the heater core to regain heater until spring. In the spring, I installed a coolant filter and so far so good.

There's also a cable that attaches to the blower door and it can sometimes pop off. It's located under the glove box and easily visible without any disassembly.

 

[etc.]

A quick test to see if your heater core is clogged is once it's warmed up, grab a hold on the heater core hoses to see if they're hot. Be sure the heater and all the way to the right.

Both should be hot.

 

[2ndhandyotaman]

I was chasing this issue last week. My problem ended up being that the cable that opens and closes the control valve was seized up. Pop yours off of the lever on the control valve and move the dial on the HVAC control and check to see if the cable is moving. There's a control solenoid that's about 1" off of the floor of the cab directly underneath of the center of the dash where the stereo is located.

I was able to use an old cable luber tool from motorcycle days to force lubricant down inside of the cable housing, mine freed up enough that it works reasonably well. I have no desire to pull the dash apart in order to gain access to replace that cable at the solenoid end. Maybe there's a way to do it without dash removal, I couldn't figure it out and my 230 lb shop ape hands sure aren't going to fit inside of that opening.

 

[MN4runnerman]

I’ll be digging around under the glove box and center console tomorrow morning and report back. Thanks guys

 

[MN4runnerman]

Found the issue. The cable to the blend door was broken, so for now I have it open and the heat works. I’m just gonna put a manual choke cable on it and operate the door independently.

 

[4Reak Show]

Don't over look blend door cable. Knob turns two cables I believe. One for valve in engine bay, one for blend door. I'm not 100% on where it goes but you should be able to see something looking under the dash. Next time there's a 3rd Gen in my shop I'll take a peek if someone here doesn't beat me to it. My 2nd gens cable is right under the glove box. If it doesn't move with the knob pull cable off of tab if it's accessible and manual swing the door and see if you get heat. I've seen cables break and come off of their guide on other vehicles

Found the issue. The cable to the blend door was broken, so for now I have it open and the heat works. I’m just gonna put a manual choke cable on it and operate the door independently.

NAILED it.

Glad you got it fixed.

 

[MN4runnerman]

NAILED it.

Glad you got it fixed.

I’m glad too it was 21* out this morning. Thank God for heated garages.

 

[amalik]

NAILED it.

Glad you got it fixed.

Sorry for my ignorance, but what the hell is a blend door?

 

[4Reak Show]

Sorry for my ignorance, but what the hell is a blend door?

Inside the HVAC unit is a little flap (door) that moves between the evaporator and heater core and blends the incoming air between hot/cold.