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My heater controls keep going straight over to hot. I dont know why it does this. I start my car and i can watch the electronic thing behind the radio go all the way to the hot side without me touching the controls. I am not sure why it does this. I was having a mechanic try to diagnose my check engine light, is it possible to cross or short something out when this is done.

Any help would be greatly appreciated.
 

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the check engine light won't be related to the climate control at all.

you're saying your control physically moves? I just did some work on my system and if I recall there is only electrical outputs from the temperature handle and no physical cable, so I don't know how this can happen...

I assume you are talking about the power servo? the big cadmium plated thing with a vacuum diaphragm on it? it only does this in "auto" mode, correct?

the rheostat may be dirty I suppose, try spraying it out with some electrical contact cleaner (the electrical stuff on the back of your climate control panel. Also, inspect the power servo.

have a look here

http://www.cygnusx1.net/Supra/Library/TSRM/MK2/manual.aspx?S=AC&P=1

http://www.cygnusx1.net/Supra/Library/TSRM/MK2/manual.aspx?Section=AC&P=17

http://www.cygnusx1.net/Supra/Library/TSRM/MK2/manual.aspx?S=AC&P=19

even after all of this, I would guess that your DVV has jammed/failed and is constantly supplying vacuum to the power servo, causing it to move. here is how to inspect it:

http://www.cygnusx1.net/Supra/Library/TSRM/MK2/manual.aspx?Section=AC&P=20

it's definitely time to break out the multimeter and the vacuum pump. Unfortunately, everything is a pain in the ass to get at and most of the dash will have to come off to check it properly.
 

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Discussion Starter #3
i know the check engine light has nothing to do with it. i was stating that a mechanic was trying to get my light to flash by running a jumper wire. I dont know what one he jumped. I also had tried to get my cruise working. I wonder if me swapping out the vsv under the hood on the pass. side towards the firewall is bad from my donor car. I dont know if it controls the heat or not.

I guess when i get out of work today i will check it. I just wish it was all cable controlled, i can actually work on stuff like that. im not good with electrical issues. I replaced my motor myself but stuff like this bothers me.

The controller behind the radio moves to cold when the vehicle has been shut off for a few minutes. then as soon as i start it, it goes all the way hot. If there is even a way to temporaly bypass this and keep it on cold then i could at least get my ac to work.

If anyone could give me a better idea of how to get my check engine light checked out then i would be in the clear for problems with car (it comes on while going down the interstate and hitting the gas up a hill). I tried to get it to flash by shorting the wire that is shown in the repair manual but i cant get mine to flash. do i have to do something else or could it be that i need to clear my codes and wait to see if it happens again.

Thanks for all the help.

(Anyone can feel free to PM and ask me about factory parts (i work for a dealer here))

UPDATE:

thanks to tireshredder
my heating problem is probably because i took out my condensor last night and the ambiet sensor located near it was disconected leaving an open circuit (max heat). I ran out of time at the shop last night and had trouble getting one of my lines off of the old condensor and couldnt reinstall my new one. I hope to have it all installed today and charged up.
 

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one vsv goes to the firewall, which in turn goes to the sub-damper near the evaporator core. It shouldn't effect your heat situation. The other VSV controls the heater valve. The vacuum circuit for the power servo (air mix damper) does not use an under-hood VSV...just the DVV. power to trigger the heater valve VSV comes from the power servo. The power servo must move (be actuated by the amplifier and in turn the DVV) for the solenoid in the VSV to be actuated and thus the heater valve opened. you're getting tons of heat, so both of these things must be happening. Not a vsv problem.

you can temporarily turn the heat off by removing the vacuum line that connects to the firewall towards the driver's side. Plug it when you remove it, though. This should allow the powerservo's vacuum to bleed down, and rest at the "cold" setting. Not sure if your a/c will work (as your rheostat may be faulty) but at least you will get ambient temperature air.
 

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Did you remove any of the a/c stuff? There is a sensor near the condenser that will make it hot all the time.
 

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There's a 1-pin connector underneath the glove box. It's cream/white. I believe if you discoonect it, and connect it to the 1-pin blue connector you will have enabled the diagnostic circuit for the climate control. I'm fuzzy on what it does, but I believe it ignores the sensors.
 

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Discussion Starter #7
Did you remove any of the a/c stuff? There is a sensor near the condenser that will make it hot all the time.
i think that is what happened to my car. I had to leave everything out (i did plug all the ac lines with rubber plugs for moisture reasons) as i ran out of time in the shop. I will find out around 5pm when i pull my car in shop

I still have a engine light that i cant get to flash codes though. I have tried to jump the 2 wire plug near my igniter and no codes flash though.

Any thoughts on that.

Again, thanks to all for the help from everyone.
 

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If you unplug any of the temperature sensors in the AC system you will get full heat all the time. You probably removed the one attached to the condenser. What year car do you have? I'd drive around with the connector jumpered you probably have the TPS wrong or bad.
 

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what year is ther car ?
Does the Check Engine lights up just turning the switch ?

To get into the diagnostic mode, 2 things are required:
1- Jumper inserted in the 2 sockets contacts
2- TPS has to be in IDLE mode.
 

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Discussion Starter #10
its an 84 p-type and i put the 6mg in it. i got a check engine light on since i bought the car. it comes on after going down the interstate for a while then climbimg a steep grade where the engine is under a load. then when i restart the car it goes away until i do that again. i havent been able to get my light to flash and tell me what it is doing. i jumped the wire that the repair manual shows. i just cant get it to flash on the dash.

I jump the wire and have the ign "ON" without engine running and light is on but wont flash any codes out. its just bothersome. i just want to know what im doing wrong.
 

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Discussion Starter #12
ok
i will try to readjust my throttle sensor. i replaced a while back. i dont know how to adjust it, but i think someone here at the dealership can help me. i will keep y'all updated.
 

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The issue with the ac temp going to hot is is the rear climate temp sensor in the center console is unpluged missing or bad. It is the little sensor in the rear of the console that has a fan attached to it.
 

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its an 84 p-type and i put the 6mg in it. i got a check engine light on since i bought the car. it comes on after going down the interstate for a while then climbimg a steep grade where the engine is under a load. then when i restart the car it goes away until i do that again. i havent been able to get my light to flash and tell me what it is doing. i jumped the wire that the repair manual shows. i just cant get it to flash on the dash.

I jump the wire and have the ign "ON" without engine running and light is on but wont flash any codes out. its just bothersome. i just want to know what im doing wrong.
That is because the 83 and 84 don't flash. The 85-6 do. You need an analogue voltage meter and count the number of needle sweeps. The old link on the 83-84 procedure is dead (Ryan Eytel's) (no Check engine on 82 BTW):

- Ignition on (engine off)
- Short the check connector near the distributor (paper click works well)
- Put analogue voltmeter leads into the EFI service connector Vf and Ei on the shock tower:
_ _
l l

That would be the 2 on the left (the bottom right should have no metal in it, pos (red) to the top left horizonal one.

No codes will give you a needle fluctuation between 5V and 2.5 V every .6 sec.

Malfunction code reading (TSRM):
"First, there will be a 5V indication for 2 seconds followed by a 2.5 V indication for another 2 seconds. Thereafter, the number of times the needle deflects between 2.5V and 5V every 0.6 sec is the first digit of a 2-digit code. Next, the number of time the needle deflects between 2.5V and 0V is the second figure of the 2-digit code. "

If more than one code then will be in sequence (lowest first) with a 2.5V indication for 2 seconds in between. The code(s) will repeat as long as the jumper is installed and the ign is on.

The codes are the same, except no knock sensor code on 83-4.
 
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