No heat or AC, blower is working

33 - Air outlet damper position sensor circuit (DI-899)
41 - Air mix control servomotor circuit (DI-902)
42 - Air inlet control servomotor circuit (DI-905)
43 - Air outlet control servomotor circuit (DI-908)

The DI-nnns are the page numbers in the service manual volume 1 that will tell you specifically how to test each of those things and pinpoint just what's causing the problem.

While it may be possible that all three servomotors and a sensor all picked the same day to flake out, it's not the way I'd bet. I'd be more likely to start with more basic questions, like, all four of these items are wired through connector A9 at the back of the HVAC control, has anybody been working behind the center finish panel lately for any reason, radio installation, whatever? Did A9 get plugged back in? That sort of thing.

Both the air mix and air outlet servomotors are very easy to get to on the left side of the heater unit, as you can see here. The air inlet servo is on the blower side of the unit and harder to get to.

-Chap

 

Hmm, glad to hear that seating A9 made some progress. No heat, hmm....

You do have one more easter egg you can make use of here, that's described on page DI-864. Once you have the test mode activated where the A/C light is blinking, the center "Temperature" knob turns into a test input you can use to directly control the various outputs and confirm they work.

Basically, the temp scale gets divided into five ranges: fully counterclockwise to about 66 F, range 1. 67 to 72 F, range 2; 73-77 F, 3; 78-83 F, 4, 84 F to fully clockwise, range 5.

If twist it all the way down to range 1 while in test mode, you get a low fan speed, the air mix servo goes all the way to cool, the position where the damper directs all air around the heater core instead of through it. (The air mix servo is the one my video shows in the post I linked above; it's very easy to see once you've got your head down there.) The air inlet damper goes for full inside-air-recirculation (that's the servo that's hard to see, but if you take out the glove box--your car's left-hand drive, I hope--you can see the damper move). The air outlet damper should be fully in "face" position, air coming out the vents on the dash. This one's on the same side as the air mix and is also easy to see once you get your head in there. Also, the output to the A/C clutch relay will be on.

Twist the knob a bit to range 2, the fan speed goes up a tad, the air mix moves a little toward warm, air inlet moves to a mix of recirc and fresh, outlet moves to bi-level. Clutch output stays on.

Twist to range 3, fan hits about half speed, air mix is midway, inlet is more fresh than recirc, outlet is "foot", clutch output turns off.

Range 4, fan a bit faster, air mix more toward heat, inlet fully fresh, outlet to the defrost vents, clutch off.

Finally twist the knob to range 5, fan runs full speed, air mix dampers fully move to heat, inlet stays fully fresh, outlet moves to combo foot/defrost, clutch stays off.

You'll either be able to verify all these things work, or you'll spot something that isn't working and that could be the problem. I can't think of much that would deprive you of heat unless the mix damper is somehow stuck in the cool position ... but the servo sensor would detect it's stuck and you're not getting a code. Unless the linkage got unhooked somehow, so the servomotor is moving to all the right positions but it's not moving the dampers. The position sensor wouldn't catch that because it's just built into the motor assembly.

The air mix damper linkage has a fun trick you can see it do at the very last stage of its travel for max heat. This heater is really a bi-level design with two totally separate air pathways for down to the feet and up to the dash vents. There are really two air mix dampers down there, one for each air path, and for most of the servo range the lower one moves from cool to warm gradually while the upper one stays put. One servo linkage controls them both. Toward the very end of its travel the linkage does an interesting sort of backflip that brings the upper damper into the heat game too. It's hard to describe but easy to see when you watch it. (Edit: I didn't describe that correctly. Both air mix dampers always move together - that's the parallelogram part of the linkage. The additional damper that moves in the "backflip" is very close to the foot output of the heater. It's shown on p. 154 of the New Car Features Manual. It's normally closed so air only reaches the foot outlets when sent there by the normal air-outlet dampers, but the backflip at max-hot opens this damper and directs some air directly from the heater core to the foot ducts.)

You have checked the engine coolant level, I hope? I remember one time borrowing a friend's car for a trip to Milwaukee and just past Chicago I suddenly stopped feeling any heat from the heater. Pulled over ASAP and, sure enough, coolant was so low there wasn't any to carry heat to the cabin. Friend told me it had been topped off just before the trip. That was a car that wanted a head gasket....

-Chap

 

How about the other dampers - the air mix and air outlet dampers? They're on the other side of the heater from the glove box (unless you're in a right-hand-drive part of the world).

If they're all working too ... have you felt the heater hoses where they go through the firewall? Hot?

There just aren't too many more choices in how to explain this. If you pump hot water through a heater core and blow air through it, the air gets hot. Otherwise one of those things isn't happening.

The electric water pump (see page DI-927) is an interesting animal. According to the New Car Features Manual, it includes a bypass valve that shunts water around it when the engine is running, through it when the engine is stopped. According to the diagrams starting at DI-927, it has only a two-terminal electrical connection, controlled on/off. What works the bypass valve isn't clearly explained. (Spring return to bypass when the pump is off?) I've never had one to look at so I can only speculate.

A problem with its control circuit, or a stuck bypass valve, might obstruct the hot water flow.

A signal from the heat/AC ECU is what drives its relay, but apparently there is no position/status feedback circuit, so the ECU wouldn't have any diagnostic code to give you if this wasn't working.

-Chap

 

Just quickly b/c I'm at work.

1. The servo motors for air mix and air outlet are on the left side of the heater, you can see them if you stick your head down in the driver's side footwell. In one of my earliest replies to this thread I posted a video, you can see them there. Also check the service manual. You'll find another book at techinfo called the New Car Features Manual, which is the best one to look in for an overview of where everything is and how it works.

2. Heater hoses - check on the engine-compartment side, I think roughly centered (between engine and inverter) - check the manual to be sure. I've never tried to fit a hand in and grab them myself, but I'm optimistic there's a way to do it. Don't forget that what you're trying to wrap your hand around is supposed to be hot.

3. Blower replacement. This is a pain. You either remove the instrument panel to get to it (long and tedious), or you cut out a part of the panel (normally hidden by the glove box, the places to cut are marked), access the blower that way, and then replace the part you cut out with a special replacement part made for the purpose (in volume 2 where it explains the procedure, it gives the part number).

-Chap

 

Ok, I think you found the right tubes, and if they were hot, as I said earlier, there aren't many choices for the problem. If you blow air through the hot coil, the air will get hot. Now we know the coil is hot, so maybe the air isn't going through it? That's what the air mix servo controls, by moving dampers to change how much of the air stream goes through the hot coil and how much goes around it.

You say the servo motors (there are two) under the driver's dash "are working", but there aren't many other places to look for the problem. If you take the air mix servomotor off so you can move the damper linkage on the heater by hand, and you warm the engine up so the coil is hot, and turn the blower on full, and move the mix dampers by hand, can you feel the outlet air temperature change? If even that doesn't have any effect, I'd have to suspect some break in the damper linkage, maybe where you can't see it.

If you can change the air temperature by moving the mix dampers with your hand, then the servomotor probably wasn't getting commanded to the right positions, even if you thought it looked like it was doing something.

Have you been behind the center dash panel more than once? You mentioned taking it off to check A9. Was it off before that? I seem to remember there is a flat ribbon cable if you get further into disassembly of the panel; I don't remember that you would encounter it if you were only checking whether A9 was plugged in.

Anyway, if the test easter egg worked with the heater going into different modes when you turned the temp dial in the five different ranges, then I think the dial must be connected.

-Chap

 

I had a linkage above to the right of the accelerator fall off when I was doing a clumsy accelerator change. It stopped all air control. I'll try to take a photo and post it.

Bob Wilson

 

Hi- This Roy from Canada - chap is quoting page numbers in volume 1 manual - email me at [email protected] and will send pdf,

 

Am I right that this is with the heater in normal operation mode, not test mode? For normal operation, what you're saying sounds right: the fan goes to high speed when you set the temp dial for either full cool or full heat. More moderate speed when set for more moderate temp.

If you put the heater in test mode first, then the temp dial has a different function, with five different ranges as I described in an earlier post. In that mode, the fan should be at low speed in the leftmost range, and get faster through the five ranges, along with the other servo position changes I described.

A couple posts up, I suggested removing the air mix servo motor (simple, three phillips screws) so you can hold the air mix damper linkage in full heat position by hand. Have you tried that yet? If you do that, after warming the engine to full operating temperature and confirming that the tubes are good and hot where you felt them before, can you feel the air temperature out of the heater changing as you move the damper by hand, or not?

-Chap

 

In your photos, the big, weird-shaped rotating cam in the top of the picture is part of the air-outlet servo system, the flaps and dampers that direct which of the (floor, face, window) outlets the air goes to. I can see that one in different positions.

The simpler white linkage below that (looks kind of like straight white pieces in a parallelogram arrangement) is the air-mix linkage, controlling how much of the air goes through the heat coil and how much goes around it (and, thereby, controlling the temperature of the delivered air). I can't convince myself that linkage is also moving in your photos. Are you sure it is?

-Chap

 

Just follow the linkage back (well, forward in the car, toward the firewall) until you find the servomotor it attaches to. If you take that motor off (three phillips screws, easy peasy) you should be able to move the linkage easily by hand. I think I suggested that in post 10. And post 15. And back in post 2 I gave a link to another thread with a video and photos of the servo motor, and also described where it's located. And also in post 4. And post 6. And post 8. And 10, and 15.

My manual is out in the car. I'll try to remember to look next time I'm out. It should also be on techinfo.toyota.com.

-Chap

 

The code 21 turns out to be the one for the solar sensor, and is normal to get any time you put the heater in test mode when no sun is shining on the sensor. It only indicates a problem if you know the sun is shining and you get the code anyway.

I always remember there is such a code, and I always forget which exact code it is....

-Chap