Heater Doesn't Work

[Silver MK3]

So the other night it was cool outside and I went to drive home. I waited for the car to warm up so I could have heat, but even when the car was warm all it would do is blow cold air. The A/C was off and the temperature was set to 85*. Even by the time I had gotten home after a 15 minute drive I still did not have heat. I researched it and I saw a lot of people having problems with the VSV on the heater control valve so I tested that by letting the car warm up and turning the heat on. The bar was pulled up and allowed the hot coolant to flow into the heater core, so I know the heater core is getting hot coolant and that is not the problem.

My car is an 87 N/A Supra with the original climate control box, not the 89+ one. The car has coolant, all the blower speeds work, and the A/C blows ice cold. I tried cycling the temperature up and down, but that made no difference.

If anyone has any input or suggestions as to what could be causing the problem it would be greatly appreciated.

Thanks in advance!

 

[hvyman]

Door could not be opening to allow the hot air in on the heater box.

 

[Silver MK3]

Door could not be opening to allow the hot air in on the heater box.

Is there anyway that I can check this without pulling the dash apart?

 

[Bmettie]

You can with a couple of test leads and a Multi Meter

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=AC&P=43
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=AC&P=45

 

[Dan_Gyoba]

Check the VSV under the hood, and that the heater valve is opening. I had mine fail (While I was daily driving, during a Canadian winter no less) and that's what happens, is that you just don't get heat, because you get no hot water. the VSV is a relatively comon failure point. The Toyota VSV is expensive, so I used the parts from this tech tip instead. The Mercedes Benz part was quite a bit less expensive (Particularly since a local Mercedes Benz dealer was a client of mine at the time) and works perfectly. I used the original Toyota electrical connector even, so it works very well.

There's a temperature sensor on the water line, so if everything is on "auto" the fan doesn't even come on, since the water line doesn't get hot.

 

[Silver MK3]

You can with a couple of test leads and a Multi Meter

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=AC&P=43
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=AC&P=45

Thanks, I missed those pages in the TSRM. I'll definitely check this out when I get time. It's like 85* out right now so hopefully it wont get cold until I get this solved.

Check the VSV under the hood, and that the heater valve is opening. I had mine fail (While I was daily driving, during a Canadian winter no less) and that's what happens, is that you just don't get heat, because you get no hot water. the VSV is a relatively comon failure point. The Toyota VSV is expensive, so I used the parts from this tech tip instead. The Mercedes Benz part was quite a bit less expensive (Particularly since a local Mercedes Benz dealer was a client of mine at the time) and works perfectly. I used the original Toyota electrical connector even, so it works very well.

There's a temperature sensor on the water line, so if everything is on "auto" the fan doesn't even come on, since the water line doesn't get hot.

I have already verified that the VSV is working. It pulled the arm up on the valve and let the hot water in like it should. It was the first thing I checked since it seemed to be such a common failure point.

 

[supraguy@aol]

Did you verify that the return hose OUT of the dash is getting hot? If it is, then the fault is with the blower box diverter.
If it isnt getting hot, then the issue is air in the heater core, and needs to be bled.

 

[Silver MK3]

Did you verify that the return hose OUT of the dash is getting hot? If it is, then the fault is with the blower box diverter.
If it isnt getting hot, then the issue is air in the heater core, and needs to be bled.

Sorry it took me so long to get back to this thread, I was real busy this week. I checked it out earlier and the hose coming out of the dash is hot also.

I assume when you say "blower box diverter" that is the same part that they were mentioning above?

I'm going to try and go through those troubleshooting steps that the TSRM has that Bmettie posted either tomorrow or Monday. I will definitely post the results back here.

 

[supraguy@aol]

Correct. Good luck.

 

[AnubisMK3]

Sorry it took me so long to get back to this thread, I was real busy this week. I checked it out earlier and the hose coming out of the dash is hot also.

I assume when you say "blower box diverter" that is the same part that they were mentioning above?

I'm going to try and go through those troubleshooting steps that the TSRM has that Bmettie posted either tomorrow or Monday. I will definitely post the results back here.

My camry had this problem a few years ago, the little door that opens the heater side of the box was stuck, a 2" holesaw and 20 mins later it was fixed and i just plasti-welded the core back into
its place

 

[Silver MK3]

Well I fixed it... I took of the glove box and lower cover panel and was dreading going in and troubleshooting the system. I starting looking around and had my trusty TSRM at my side and law looking at the step that talks about the heater servo motor moving smoothly between warm and cool. A while ago I had mounted some LED foot well lights on both sides of the car to replace the single one on the driver side. I mounted these lights at night so I could see how the lights would look. Apparently I had mounted the passenger side light onto the servo motor for the heater. I even managed to connect it to the arm on the servo motor so it was stuck in the cool position and not allowed to move over to the warm side. I remounted the light and now the heater works beautifully.

That's what happens when you try to mount LEDs at night laying upside down under the glovebox with the lights shinning in your eyes, you mount them onto the heater servo motor and loose heat...

Thanks for all the help guys, I feel like an idiot, but at least I'm a warm idiot.

 

[nitroneon85]

I'm glad it was that easy to diagnose. I'm having the same problems with my 88. I checked the control valve and the rod is moving smoothly and gong up and down. I heard someone say before to lower the heat to 65 and raise it to 85 and listen by the glove box for a motor sound to open a door or what not. I did that and heard no noises. What is down there and is that maybe the problem? Alsi the hoses by the control valve are warm but not too hot to hold onto, and the hose over by the master is cool. Thanks for any assistance.

 

[Silver MK3]

I'm glad it was that easy to diagnose. I'm having the same problems with my 88. I checked the control valve and the rod is moving smoothly and gong up and down. I heard someone say before to lower the heat to 65 and raise it to 85 and listen by the glove box for a motor sound to open a door or what not. I did that and heard no noises. What is down there and is that maybe the problem? Alsi the hoses by the control valve are warm but not too hot to hold onto, and the hose over by the master is cool. Thanks for any assistance.

I would think if the hose on the driver side is cool than that means the heater core isn't flowing correctly.

 

[nitroneon85]

Would a lower temp thermostat make a noticeable decrease in water temp? I think I had a 170 put in, that's 25 degrees colder than stock? I'm afraid of the heater core issue cause it sounds hard to do, although I had the dash out already while doing my burgundy to grey color change. Thanks

 

[Backlash2032]

No.

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[nitroneon85]

And what about not hearing the blend door actuator moving? Is that a concern?


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