No A/C or heat

My 2000 Tundra 3.4l manual blows air, but no heat or a/c. I am a new owner, so not sure how or when the problem started.

No fan delay when air is turned on. All controller settings work to change intensity, vents, and the a/c switch engages the a/c compressor. Heater control valve moves when switched and hoses on both sides get hot. No engine codes. Not sure what's going on behind the dash.

Is something clogged? https://www.youtube.com/watch?v=GUD3O1g_FkM

What else should I look for to diagnose the problem?

 

Weird. They're both separate systems. Does the green light on the dryer (cylinder unit in front of radiator) light up when the AC is blowing? If no light, you're low on refrigerant. Not sure what to tell you about the heater. Just make sure your thermostat opens and you're truck doesn't overheat. A stuck thermostat will cause the heater core to not give off any heat. If the engine temp is always low, it's stuck open. If the engine begins to overheat, it's stuck closed.

 

Engine temp is perfect according to the dash heat gauge. Refrigerant is at the right level. I will bleed the coolant just in case there's air, but doubt it.

I'll check for a green light.

 

Turbo 3.4 for the win!

 

@Mr.bee What turbo should I put on this best truck ever made in my humble but correct opinion?

 

Wait - let me get this right.

When you push the A/C button in the dash with car running, the A/C compressor kicks on, and idle changes slightly?
Both coolant hoses going in/out of the firewall to the heater core are hot when the engine is hot, therefore we know the heater core is not clogged?
Fan controls work to raise/lower the fan speed, and the vent mode change control works also?

But, with the engine fully warmed, A/C on and AC clutch clearly engaged, rotating the hot/cold knob all the way until it clicks on the blue/cold side produces no cold air, and likewise, rotating the hot/cold knob all the way to the hot/red side produces no hot air?

I'd need to dig to understand how the hot/cold knob works on the HVAC controls before I could take a jab at this. Like, on other vehicles I've owned the knob controlled servos/doors that would route the air coming from the blower motor through the compartment with the heater core and/or the evap core.

Assuming 1st Gen Tundras are the same, I'd suspect either the control (knob, or the control box that knob sits in) is bad, or the servo(s) that control airflow to the heater core and evap core are bad. You can't just swap out the controls with any other truck either, unfortunately.

If 1st Gen Tundras use one servo/door with three positions, it's possible that servo or its wiring could be bad, I guess?

Curious: Are you in an area with rodents/mice, or was the truck bought from an area with them?

And for shits n giggles, I assume you checked all the fuses, checked the harnesses on the back of the control unit?

 

Oh, I thought the truck in the vid was yours. My bad. Tiny turbo. Find something that starts pushing boost under 2krpm.

When the fan is on, does it move air? Like you can feel the force of the air moving?

 

@shifty` yes, compressor kicks on and idle responds when I push-in the a/c button. I just double checked: hoses in and out and on either side of the actuator were cool before starting, then got very hot at engine temperature with heat on and engine running. All fan controls work, every setting. I did not confirm if the hot-cold knob is on correctly, but feels right.

Rotating the hot/cold knob to cold with a/c button light on produces very slightly cool air and knob switched to hot with a/c off produces very slightly warm air (both close if not equal to air temp). It is hot out, so perhaps my reference is off, but does not feel like hot air in other cars.

I plan to get behind the dash soon to install the original radio, so will take a look there then. Open to ideas... I'll research what you noted above.

I suspect that that car spent a lot of time sitting in a garage in West VA (zero rust anywhere BTW, and original frame). I wouldn't rule out mice. Northern, VA, where the car is now, is mostly inhabited by rodents :\

The relevant fuse is good, but I have not yet checked the heater/ac relay - still figuring out how to get it off. Need to take a closer look at the harness, probably this weekend.

 

@Mr.bee Yup, forceful air. Thanks for the turbo tip.

 

Do you have a UV light? Look all in the engine bay for signs of a leak.

with the ac running for a while do you get any condensation dripping out of the little tube?

 

"Blend door". It dawned on me what it was called right when I tossed a steak on the grill. Don't ask.

Maybe the blend door is stuck. That's the trapdoor in most cars that controls the mix of hot/cold air flow.

I'd probably pop out the blower motor and check the evap coil area for debris and signs of rodents.

I'd also start digging through the manual to find where the blend door and see if it's properly opening/closing.

And I'd double-confirm the AC compressor is actually locking/kicking on.

 

If the compressor kicks on(AC magnetic clutch), that is saying the Heater fuse, Heater Relay and AC fuse, are all doing their job. There is no AC relay.

from 2000 EWD....

 

Edit: This thread covers control binding (thanks @bfunke) and belongs here: https://www.tundras.com/threads/vent-control-binding-solved.58386/


Here's a video of a guy working through ductwork diagnostics in an '05, which is where I'm leaning. I found a part number for the blend door servo, I've just never seen anyone having issues with theirs. Happens a LOT on GM trucks, most have 2-3 servos and they can go bad multiple times over the life of the vehicle.

It could be controls are binding. Only way to know is to expose the driver's side of the center dash and watch things as you move the knobs? But this guy at least shows some insides:


https://www.youtube.com/watch?v=7vToAwnD5TM

 

And especially pay attention to the 11m12s mark, I think that is the 1 major thing you need to check.

If it were heat, I'd tell you to pay close attention to the 10m20s mark.

 

Here's the same guy showing how to get to the front part of the controls - but the heat/cold blend above at 11m12s mark, you'll access that from the floorboard.

https://www.youtube.com/watch?v=0NNZ5bGOgSw

Or if you prefer Sue from 1A Auto's breakdown, this also shows you how to get into the dash for the knob portion, but not the blend door (I'd be checking both).

https://www.youtube.com/watch?v=A1ivBNr8ZzY

 

@shifty` I pulled the dash and and cables seem to be working fine. Next is to check the blend door. Thanks so much for the info.

 

I pulled apart much of the dash and as far as I can tell all components are working as they should, including the blended door actuator. I've seen videos on calibrating the blended door for other trucks by removing the HVAC relay. It's a long shot, but I want to try removing the heater relay and following the calibration steps that work in other trucks. However, I cannot figure out how to remove the relay w/out breaking whatever is holding it on. There are supposedly tabs on either side (which side, not sure), but I cannot see or feel them. How do I remove the heater relay without breaking it?

 

My guess is barely enough charge in the AC to trip the pressure switch and a stuck/brokendisconnected heater core flap - see the first vid shifty posted above for your all the flaps and levers should look and move.

Regarding the AC, does the low pressure pipe in the engine bay get really cold? Is the high side pipe hot? What do you see in the sight glass?

 

@fivil heat fixed - an arm that controls the heater core flap via a small rod was disconnected. Had to put my head way back there to see where it was disconnected.

AC: what I think is the low pressure hose gets cool, not cold (lower, thin pipe in the picture). The high side pipe (upper, thick pipe) gets hot. Something is happening in the sight glass, but not sure how to interpret it. Swirling, maybe tiny bubbles.

 

Well, you know the heat issue now.

For cooling, if you're seeing several little bubbles in the glass, there's a solid chance you're low on coolant. A couple is normal. Enough to classify as 'foam' would be a sign of low coolant. You'd really need to have someone throw gauges on it to check for sure.

If it's low on coolant, it's supposed to be a sealed system; a sealed system can't loose coolant. Would suggest a leak in the system. Could be something as simple as a worn schrader, or as big as perforation in the evap coil, or a blown seal in the compressor. Only way to know for sure is contrast dye, which an HVAC shop would (should) use when topping off coolant for you.

I don't recommend going to "general" repair shops for AC. Find a shop that specializes in automotive AC specifically. Make sure they have 4.5+ stars on Google with at least a few dozen reviews.

 

Damn I wish the ridgelines had a replaceable filter drier

 

@shifty` Thanks again. There may be no bubbles. The coolant is not low. Perhaps I just need to recharge the Freon. I'll do some more research this weekend.

 

Freon is coolant.

No bubbles can be a sign of overcharged, no coolant, or just the right amount of coolant. This is the best sight glass info I can find quickly: https://autoacrepair1.com/auto-a-c-sight-glass-diagnosis/

 

@shifty` This is all new to me. I had no idea about the sight glass. Here's what I see when it's running. I can get another video with starting and stopping. https://photos.app.goo.gl/b9hQKWfam6EXFGA47

 

Hard to say for sure, but given it's not "still" and is definitely stuff swirling around, and looks half empty, I'm guessing you're low on coolant.

Without having gauges on it, you'll never know for sure. You could refill it will-nilly with the correct coolant, but without knowing how low it is, you risk over-pressurizing.

This is really a case where you'd need to consult a professional to check.

 

You are describing premature gas expansion indicating low charge. The low side pipe goes from the firewall (it's the fatter one) to the compressor, is that pipe getting cold?

 

He said cool but not cold, probably low on frezon

 

I've noticed in the last few years, everyone is spreading lies about sight glasses. Shifty, your link is one of these BS sources. Sight glasses lead to more misdiagnoses than diagnoses, so you don't see them much anymore, it's a complicated subject.

Video makes it easy! System low charge. This also means you have a leak somewhere (probably the schrader valves), spray soapy water and look for bubbles.

 

Neither of those pipes should be cool or cold. High pressure gas line should be hot, and high pressure liquid line should be warm.

He described the high side liquid line being cool, meaning expansion is taking place in the wrong location.

 

But we can both agree on a low charge correct?


Edit; actually after re rereading that and seeing what pipes he was referring to, it’s probably a clogged drier if he feels any kind of “cool” off the condenser line