my supra blows hot air all the time

[zuprax85]

hi guys, i got a 85 supra 5 speed, with automatic climate, my ac doesnt work due a condenser leak, but my problem is, always blows hot air, not warn, just hot...but there is the trick here, there kind of solenoid behind the dash, have 2 vacuum hoses, when i disconnect this, start blowing just air, i replace this solenoid twice and still doing it, i replace the complete heater control and nothing...could be something else? is so complicated for me i cant figure out what is going on!!! HELP !!!! AH MY BLOWER MOTOR the low position doesnt work i replace the blower motor and the same...HELP!!!!

[9Teen86]

I think this has been covered before. Searched and found this from a previous thread, see the part about the ambient air sensor, if it is missing or disconnected, you will get heat all the time:



. Heating and Air Conditioning system

No Heat:
Two simple things to check first.
First, if your rad is low on fluid, your heater will not work well, as it gets no fluid. Simple to check.
Second, If your thermostat is stuck open, it will take a long time for the car to warm up, so it will take a long time for the heater to give you hot air. You can of course check this by watching your temp gauge and seeing if it takes a long time to rise. You should start to get some warm air from the heater as soon as the temp gauge rises from its resting place. Air should be pretty hot when it gets up about a quarter of the way up the gauge. If not, start to check the heating system.



It IS possible to have toasty warm heater hoses and still not get heat in the cabin. I had heater/climate control system issues to solve in BOTH of my Supras, and I ended up learning a LOT about how the system works. So here comes Climate Control 101 (note that almost all of this applies to both the MKII and MKIII):
· The vacuum operated heater valve on the firewall just lets the hot coolant in and through the heater core or not, NOTHING more. It is opened (the vacuum is applied) when the coolant gets above a certain temperature. The coolant temp is read by a sensor on the thermostat housing, and the signal is fed to the Vacuum Switching Valve (VSV) located on the passenger side fenderwell beside the windshield washer fluid reservoir. When the coolant is warm, the VSV allows the vacuum to be applied to the heater valve on the firewall. The reason for this is to keep the coolant in the engine until it gets warm, letting it get up to operating temperature faster. A too-cool running car can be as bad in some ways as a too-hot one. Your thermostat does exactly the same thing, but for the radiator.
· The temperature of the blown vent air is controlled by a flapper system inside the dash, NOT just by the hot coolant running through the heater core. Some air goes through the heater core, some goes around it by way of a different duct. The amount of air that goes through the core - getting heated - controls the temperature of the blown air. It’s sort of like mixing hot & cold water by playing with the faucets. You can get any temperature water, not just the two extremes, that way.
· The flap that adjusts the temperature is NOT connected to the “temp” lever on the dash like it is on most average, boring cars. It is controlled purely by a vacuum operated servo motor. Unfortunately, this is also exactly why you can have the vacuum valve on the firewall open, the temp lever on “85/full hot” and STILL not get heat.
· Why did they do it this way? So the “automatic” climate control can make its own adjustments and keep the cabin at a constant temperature without the dash controls moving. The temperature flapper has to be able to move throughout its range with NO input from the driver. This means it is always under the climate control ECU’s control, including when the system is in “manual” mode (see where this is headed?).
· How does the climate control know whether to blow hot or cold? In manual mode, it just looks at where the temp lever is set and adjusts to hot or cold based on that. In auto mode, though, it instead compares the temp lever’s setting to the cabin temperature and chooses hot or cold based on that. How does it know what the cabin temperature is? Well, inside the center console is a little fan/vent assembly. It sucks air in from near the base of the center console between the rear seats. It has a sensor in it that measures the temperature of the air being sucked in. We will call this gizmo the "Cabin Temperature Sensor". The ECU uses this measurement to adjust the temperature flap and the fan speed as necessary.
· The Automatic Climate Control system must also know the temperature of the outside air. It uses an "Ambient Temperature Sensor", mounted under the hood. It is a small round black sensor, mounted on the metal bracket that holds in the A/C condenser, towards the passenger side. If it is disconnected, you will get max heat all the time, no matter what your settings are. If there is a short in this circuit, you will get max cooling all the time. So, an easy test is to disconnect it and see if you get heat. Then, you can jumper the connector, and see if you get cool air only. If you have a multimeter, you can check the sensor’s resistance. It should be 0.4 to 0.6 k ohms when the ambient temp is between 32 and 77 deg Fahrenheit. Replace if faulty.
·
· Here’s the catch: This cabin temperature sensor is integral to the system, even when it’s in “manual” mode. Normally, the climate control ECU can just ignore the input from the sensor when you manually set a fan speed. But there are two conditions the climate control ECU cannot deal with: a short circuit and an open circuit. This is because the cabin temp sensor’s resistance normally falls into a very small range, which doesn’t include 0 or infinite resistance (short or open circuit).
· Because of the ECU’s design, when the cabin temp sensor is removed (unplugged, disconnected, an open circuit) the climate control ECU sees the cabin as being “infinitely cold” and puts the system into MAXIMUM HEAT, no matter what the dash controls are set to. And when the temp sensor is shorted, the ECU sees the cabin as being “infinitely hot” and puts the system into MAXIMUM COOL, again completely ignoring the dash settings. I learned this the hard way when I pulled out my center console to do some work - unplugging the temp sensor in the process - then had to go somewhere on a hot summer day. I about barbecued myself because the system blew hot air, no matter what I did.

So if the temperature sensor circuit has a short in it somewhere, you can play with the dash controls and all the stuff under the hood forever and you won’t get a bit of heat out of it. The quickest way I can think of to test it would be to remove the center console (the rear part, from just behind the gearshift back) and unplug the wires to the sensor. If you get heat, and lots of it, you have a shorted temp sensor. If you still don’t get heat, measure the resistance on the “car” side of the sensor’s plug to make sure you don’t have a short further up the internal wiring. You’ll need to check your manual for which two wires to measure between. If you definitely have an open circuit and STILL can’t get heat, you probably have a failure somewhere else in the electric part of the climate control. This could include broken wires going to the temperature flap servo, broken wires going to the ECU, or even a bad ECU

3. Clicking from heater system behind dash
The solution to the “mystery” click problem, contributed by Vern.
This is a common problem with Mk2's. The noise is from the relays that control the heater valve actuator (the gold thing behind the radio). The slide resistors in the heater controls can wear out, and have bad internal connections with the sliding arms (levers). Basically, one second they would send a voltage signal to the actuator circuits, turning on a relay, and the next, the internal connection would break, the voltage signal would go away, and the relay would click back off. The signal can change very rapidly due to road vibration, or whatever, and that change between on and off can wreak havoc on the relay systems back there. The noise can be really annoying, especially if you are cold and the heater just wants to make noise, and not heat!
As soon as I replaced all those switches the noises pretty much stopped, and the heater works just fine. Major PITA job, but worth it.
All this crap could have been avoided if Toyota had just given our cars cable controlled manual heater valves like every other car, but then we couldn’t have had “Automatic Air Conditioning”. But luckily, the Supra is not like every other car, and I love it!

[supkar]

Well, a lot of people on this site blow hot air all the time. Heh, heh.

[tiksman]

If the sensor for the ac in the center console is unpluged you will get heat all the time. Been there done that.

[CJSREDPRA]

AH MY BLOWER MOTOR the low position doesnt work i replace the blower motor and the same

Problem is NOT the fan blower motor.

Problem IS the blower fan speed resistor. Replace. Order a new one from Toyota. Should be under $10. Make sure you order the right one. (there are 2 versions. 1 for cars w/o Auto A/C (like the Celica's), and 1 for cars WITH Auto A/C (our cars)).

[zuprax85]

I GOT HOT AIR ALL THE TIME !!!! if i let the dual vacuum valve connected it all the time it blows hot air, even in manual position, but if i deisconnect this wires just blows air, there are two in car sensor, one is close to the ashtray right? and the other one in the dash close to the windshield? should i test both? i will check everything even the VSV, thanks guys for this advice....

[dannymk2]

Problem is NOT the fan blower motor.

Problem IS the blower fan speed resistor. Replace. Order a new one from Toyota. Should be under $10. Make sure you order the right one. (there are 2 versions. 1 for cars w/o Auto A/C (like the Celica's), and 1 for cars WITH Auto A/C (our cars)).

where is the resistor? in my car, air blows air all the time, even with the fan off. its hot or cold depending on what the temp selector is set to.

[zuprax85]

hey guys, guess what!!! i found the problem...yesterday i was reading this TSRM about how to test the complete system, something about to change the normal connector to the blue connector AND the problem was there, the NORMAL connector was not a connector, it was just fragments of wires, i cleaned and make a secure and safe electrical connection and the power comeback to the Dual Vacuum Valve and the clicking start but also the power servo steam keep moving when i set a different temperature...im so excited!!!! now i can control the temperature, and the auto system works perfect!!!

and i found where the resistor goes, i pull it off and is not in good condition, so i check toyotapartscheap.com and i ask about the resistor, they said :

RESISTOR # 8863514080 $ 5.47 + SHIPPING. 2 DAYS TO ME, THEN SHIPPING TO YOU. THANKS JEFF

Thank You for your interest in using www.ToyotaPartsCheap.com We appreciate your business!!! 1-888-716-6779

thanks everyone i hope this will help!!!

[zuprax85]

if you have the clicking noise i have the part number of the dual vacuum valve 88690-14530

OEM Catalog
Item Number MSRP Core Price Price
8869014530 $67.88 $0.00 $54.30

VALVE ASSY, MAGNET

use www.toyotapartscheap.com

[jrok]

hey guys, guess what!!! i found the problem...yesterday i was reading this TSRM about how to test the complete system, something about to change the normal connector to the blue connector AND the problem was there, the NORMAL connector was not a connector, it was just fragments of wires, i cleaned and make a secure and safe electrical connection and the power comeback to the Dual Vacuum Valve and the clicking start but also the power servo steam keep moving when i set a different temperature...im so excited!!!! now i can control the temperature, and the auto system works perfect!!!

and i found where the resistor goes, i pull it off and is not in good condition, so i check toyotapartscheap.com and i ask about the resistor, they said :

RESISTOR # 8863514080 $ 5.47 + SHIPPING. 2 DAYS TO ME, THEN SHIPPING TO YOU. THANKS JEFF

Thank You for your interest in using www.ToyotaPartsCheap.com We appreciate your business!!! 1-888-716-6779

thanks everyone i hope this will help!!!

thats the test wire it bypasses temp control and just makes it manuel control
the prob i had was the amient air sensor by the front of the car