Thermostat housing cover sensors/switches

[Gargoyle]

Hey all,

The car that I bought is a 1990 turbo/ auto and I have an extra wire swinging around in the engine compartment. It is purple with white and I think it is for the number two fan. My problem is that I also have the wrong thermostat housing cover (part the hose hooks to), and I only have two sensor holes on it. I currently have the BOV and a single wire spade (white) on the housing.

I have bought a new housing but Toyota is having a hard time finding the sensor/switch. Does anyone know the Toyota name for the unit and/or have the part number off of it. It is the third sensor/switch on the housing cover and installs at an upward angle into the cover.....any help would be appreciated.

Thank you,
Brian

 

[Shawndude]

I think you're describing the A/C off switch. If so, it just turns off your air conditioning when close to overheating. There is only one coolant fan switch on the Supra.

You can find part numbers and what other cars use it here:
http://www.cygnusx1.net/supra/library/EPC/MKIII_NATO/index.html

Here would be the switch:
http://www.cygnusx1.net/supra/library/EPC/MKIII_NATO/291420/8715_1.html

Unfortunately there are bazillion different part numbers and models for these, and both the fan and the A/C off switch share the same prefix.
http://www.cygnusx1.net/supra/library/EPC/MKIII_NATO/parts/88625C.html
http://www.cygnusx1.net/supra/library/EPC/MKIII_NATO/parts/88625.html

 

[Gargoyle]

Thanks so much for the help, I should be able to get the part with this information.

Brian

 

[Gargoyle]

In case anyone else trips across this thread and was wondering the part number is 88790-24090.....Thermistor Assy. and runs around $50.



Brian

 

[3p141592654]

The reason for the confusion is that that page shows all 5 sensors. Look at the "MODEL" column and you will figure it out. It breaks all the rules of the usual Toyota EPC. Also the sensor numbering (No. 1, No. 2, etc.) is not consistent with the TSRM adding to the confusion.

 

[7M-GTE]

this might help me out a little...

 

[jetjock]

I think you're describing the A/C off switch. If so, it just turns off your air conditioning when close to overheating. There is only one coolant fan switch on the Supra.

Shawndude, I've read this from you before and it got me curious. Not saying you're wrong but since that switch isn't shown in either my service manual or my EWD I went and checkd it. Mine is open when cold and grounding it doesn't disengage my AC clutch. In fact, grounding it doesn't seem to do anything as near as I can tell. I assume it's connected to the AC amplifier? Can you verify what it's connected to and it's function?

 

[Shawndude]

JJ it may vary by location?

Here are the switches:
http://www.cygnusx1.net/supra/library/TSRM/ac/AC_33.html

Here are the wiring diagrams (the switches are on top right)
http://www.cygnusx1.net/supra/library/TSRM/ac/AC_05.html

And here are the switches in another wiring diagram but labeled backwards?
http://www.cygnusx1.net/supra/library/TSRM/d/D_30.html

And in colour (next page too)
http://www.cygnusx1.net/supra/library/Wiring/pages/Page_143.html

I figured this out a few years ago sitting in front of my 1988 TSRM, after my car got hot and the A/C shut off and I wondered how it knew.

But I can't remember exactly how I deciphered the diagrams and my TSRM has fallen apart into a useless pile of random pages by now. :icon_conf

 

[jetjock]

Gracias Amigo, for taking the time to hunt all that down for me. Your manual must be like mine. I bought both the same day I bought the car and have since probably spent as much time studying as driving the car. It's dog eared for sure

I can certainly see why you think what you do because you're correct. Looking that those schematics the switch does appear to do exaclty as you say. The problem is my manual (and car) is quite a bit different from the online one. The 87 manual (being the first year for the turbo) is lacking in many ways. No color, among other things.

Not to say it isn't accurate for 87 model years, I've found it is, just that neither it or my EWD book show this switch anywhere. Nor is it located per the first link in your post. It's located as per another post with photo you made a week or so back: low on the T stat housing behind the PS tank. It's still not referenced in either book though, by pictorial or schematic. Nor do I have those relays the online manual shows. This switch has always been somewhat of a mystery. As I said, it's open when cold and grounding it's single lead doesn't seem to do anything no matter how I configure the climate control system.

The only coolant switch I have that's connected to the system (other than for the condensor fans) is a dual unit, one of which that keeps the blower off when the system is in auto mode until the coolant warms, but that switch is located near the heater core and *is* shown in my books. I'm not talking about the dual A/C pressure switches either as their not in the coolant line. (I'm EPA 608 Universal and 609 MVAC certified so I'm not a total dummy when it comes to that stuff)

I dunno. All this seems to be a case of wiring (and manual) changes in the 88 and forward model years. Since it doesn't apply to me I'm not going to worry about it but I'd still like to know what my switch does because I may have a problem and not realize it. Without it being shown on the schematic I'll have to track it down the hard way unless someone else here has a clue. Either that or go back to not losing sleep over it. If nothing else this reminds me I need to remember when offering tech advice that later cars are different in many ways. Thanks again...

 

[Jetfixr757]

Thanks so much for the help, I should be able to get the part with this information.

Brian

The engine in your car is a JDM engine the USDM has 3 the JDM has 2 ports on the thermo neck.
William

 

[yannis-supras]

The engine in your car is a JDM engine the USDM has 3 the JDM has 2 ports on the thermo neck.
William

William I have both (the jdm 2-port currently on the engine) and actually I was wondering what the 3rd port on the usdm -and ukdm apparently- is for and if it offers any advantage? I was thinking of swapping if there is any benefit.