A/C coolant Temp switch - Location (2 Viewers)

[Richard Luksozek]

Well I have finally gotten around to finishing the A/C after the 4JJ engine transplant and all works except for one thing and need help from the forum. Attached is the wiring diagram showing the A/C Coolant Temp Switch. I have worked out that the Coolant Temperature Cutout Relay is part of the internal circuit of the Amplifier and the A/C Coolant Temp Sw is external. When I bridge the (B)lack to (N)utral then the clutch pulls in. Here is my question. Where is the A/C Coolant Temp Switch? If anyone can help me locate so I can fix it then my A/C will be done.

 

[jblueridge]

What vehicle and year?

 

[Houser]

Mine is colocated with the fan dial.

 

[Richard Luksozek]

What vehicle and year?

Land cruiser 70 series Troop carrier HZJ75 1996

 

[Richard Luksozek]

Mine is colocated with the fan dial.

View attachment 3608437

Mine is colocated with the fan dial.

View attachment 3608437

My fascia looks a little different but basically the same. The fan has to be running to supply power to the Low Pres Sw which is on the TX valve in the evaporator. I've tested that and the rotating dial, part of the fan speed sw, is a temperature thermostat and have also tested that. Cables to it are Yellow. So am at a bit of a loss as to what/where the Coolant Temp Sw is.

 

[jblueridge]

My BJ74 does not have that switch.
Does the word Coolant here mean Refrigerant/freon?
Do you think it is a fail-safe to protect the system?
When you bridged or bypassed it, did the ac clutch stay on and not release or did the clutch release according to the thermostat dial on the dash?

 

[ToyotaMatt]

Well I have finally gotten around to finishing the A/C after the 4JJ engine transplant and all works except for one thing and need help from the forum. Attached is the wiring diagram showing the A/C Coolant Temp Switch. I have worked out that the Coolant Temperature Cutout Relay is part of the internal circuit of the Amplifier and the A/C Coolant Temp Sw is external. When I bridge the (B)lack to (N)utral then the clutch pulls in. Here is my question. Where is the A/C Coolant Temp Switch? If anyone can help me locate so I can fix it then my A/C will be done.

View attachment 3608353

without knowing any vehicle particulars of any kind ,


this is all i got ...


any look like yours ..........?

.

 

[Richard Luksozek]

without knowing any vehicle particulars of any kind ,


this is all i got ...


any look like yours ..........?


View attachment 3609008


.

Thanks and yes I realised I was asking the impossible when I got a similar question from jblueridge above.

Truck is Land cruiser 70 series Troop carrier HZJ75 1996. The problem I have is I can bridge the wires at the A/C Amplifier that go to the A/C coolant Temp Switch to earth and the clutch pulls in but I don't know where the switch is or what it looks like so that I can fault find further.

 

[Richard Luksozek]

My BJ74 does not have that switch.
Does the word Coolant here mean Refrigerant/freon?
Do you think it is a fail-safe to protect the system?
When you bridged or bypassed it, did the ac clutch stay on and not release or did the clutch release according to the thermostat dial on the dash?

Fail safe? Good question. It may not be a "switch" as such but perhaps a LOW gas temp. Great point. There is a coil temp sensor and pressure switch on the Liquid line at the TX valve in the evaporator. I've tested the Pres sw and it is fine and operates as a Low Pressure cutout which turns OFF the compressor when low on refrigerant. Had to charge with gas for this to close so that I could test the system. The wiring diagram doesn't show a LOW Temp cutout and if this was then I assumed it would have been a Normally Closed contact, opening on LOW temp. But its the opposite, N/O. I need to investigate this a bit more Tks.

 

[jblueridge]

If the system runs normally with this thing bypassed, you could make that bypass permanent.
My BJ does not have that device so I think it is something new-fangled to protect the system.
Its confusing if the switch is normally open but must close for the clutch to operate.
Maybe contact Engineer8000 on MUD (Cape Fear Electronics). He has tested and repaired many ac amplifiers and might know about this switch and the circuitry

 

[Richard Luksozek]

If the system runs normally with this thing bypassed, you could make that bypass permanent.
My BJ does not have that device so I think it is something new-fangled to protect the system.
Its confusing if the switch is normally open but must close for the clutch to operate.
Maybe contact Engineer8000 on MUD (Cape Fear Electronics). He has tested and repaired many ac amplifiers and might know about this switch and the circuitry

Tks and yes I agree it could be something to sense the Refrigerant temperature and if this is the case then quite possibly its now gone when I replaced the 1HZ for the Isuzu 4JJ motor. New compressor suction and discharge lines. I can see why you would want to have a LOW temp sensor in the suction line to protect the compressor from liquid refrigerant in the event of a TX valve sticking open. Anyway I'll dig a bit longer and contact Engineer8000. If nothing then, as you suggested, bridge it out. Thanks for your input.

 

[Richard Luksozek]

Just another thought was the A/C coolant Temp Sw may in fact be engine Water Coolant Sensor. Separate from the Instrument Gauge, this is working. If this is the case then it would certainly be gone since I now have and ISUZU 4JJ motor in the Troopie. Plan is to fine where the original sensor was mounted to locate the wire, should still be there, then ground/bridge it out.

 

[jblueridge]

Have you run it long enough with the thing bypassed to confirm that the dash "thermostat" dial is shutting the compressor off when desired coldness is reached?

For 2 years I ran my system with just a toggle switch to provide power to the clutch directly. i would "cycle" the compressor on and off while driving along the interstate. A pain but far better than crossing the Great Plains with no AC.

When Engineer8000 tested my AC amplifier, he told me some stuff that made me realize I did not know how that little box worked.
A lot of good information in his head.

 

[prwillard2]

Have you run it long enough with the thing bypassed to confirm that the dash "thermostat" dial is shutting the compressor off when desired coldness is reached?

For 2 years I ran my system with just a toggle switch to provide power to the clutch directly. i would "cycle" the compressor on and off while driving along the interstate. A pain but far better than crossing the Great Plains with no AC.

When Engineer8000 tested my AC amplifier, he told me some stuff that made me realize I did not know how that little box worked.
A lot of good information in his head.

This is an interesting work around. I may end up having to do this as my clutch will not engage either right now after removing the extra Omani wiring from my troopy.

 

[Richard Luksozek]

This is an interesting work around. I may end up having to do this as my clutch will not engage either right now after removing the extra Omani wiring from my troopy.

It seems to be common topic among enthusiasts who have made some mods to their beloved truck. From another site, the same discussion which talks about the A/C Water temp switch in the Service Manual and snip-it from the manual attached. This discussion ended up the same as your suggestion. Bridge it out. It seems there are two water temp sensors in the Troopie, at least with the 1HZ's sent to Australia. One up near the thermostat (outlet into the radiator) and another down half way on the engine block (Intake side). This is the A/C water temp switch and shuts off the A/C when engine temp reaches a certain level. The drawing shows N/O but the discustion suggests its actually N/C and opens when temp is high which disengages the clutch. Since my 1HZ is gone then the sw doesn't exsist So all I have to do is trace out the wire and earth it, job done.

 

[HZJ75 FARMER]

It's a sensor for engine coolant temperature, when your engine is starting to run hot it cuts out the airconditioner to reduce the load on the engine.

Yes, your airconditioner will work perfectly without it. But if there was somewhere on the new engine you could fit the sensor, it might be a good idea to have it, for the reason it is on the system in the first place

 

[Richard Luksozek]

It's a sensor for engine coolant temperature, when your engine is starting to run hot it cuts out the airconditioner to reduce the load on the engine.

Yes, your airconditioner will work perfectly without it. But if there was somewhere on the new engine you could fit the sensor, it might be a good idea to have it, for the reason it is on the system in the first place

Thanks and very good point. I have to remake the water outlet pipe from the engine to Rad at some point which is where I have reinstalled the Water Temp Gauge sensor so will add an additional fitting for the A/C Water Temp cut sw. For the moment I'll bridge it out once I find the wire. The old Troopie loom has been neatly taped and wrapped away so have a bit of work to unwrap it all. Blue/Black wire, how hard can that be? lol Remove the glove box, unplug the A/C amplifier and trace the wire out.

 

[Richard Luksozek]

While working out how to setup the circuit to energise the clutch (trace the wire and bridge it out), another question comes to mind. How do you PREVENT the clutch from energising when you want the blower to run in HEAT? The circuit diagram doesn't have and A/C Cool On/Off switch of sorts. I can only assume the thermostat adjustment that jblueridge and Houser rainsed earlier on. I reached out to Engineer8000 but he hasn't worked on the '97 model Troopie Amplifier so couldn't help but suggested perhaps the thermostate mentioned would play a part in controlling the clutch when heater is on. Ok so this is another thing to test when I trace the A/C Coolant sw wire and perhaps, rather than bridge it, I might have to run it to the dash as Cool On/Off sw to manually turn it off the clutch when the heater is on. Not ideal but I don't see the point in trying to cool the cab when I'm also trying to heat it, appart from defrosting the windscreen perhaps. Anyway will update this once I do more testing.

 

[HZJ75 FARMER]

While working out how to setup the circuit to energise the clutch (trace the wire and bridge it out), another question comes to mind. How do you PREVENT the clutch from energising when you want the blower to run in HEAT? The circuit diagram doesn't have and A/C Cool On/Off switch of sorts. I can only assume the thermostat adjustment that jblueridge and Houser rainsed earlier on. I reached out to Engineer8000 but he hasn't worked on the '97 model Troopie Amplifier so couldn't help but suggested perhaps the thermostate mentioned would play a part in controlling the clutch when heater is on. Ok so this is another thing to test when I trace the A/C Coolant sw wire and perhaps, rather than bridge it, I might have to run it to the dash as Cool On/Off sw to manually turn it off the clutch when the heater is on. Not ideal but I don't see the point in trying to cool the cab when I'm also trying to heat it, appart from defrosting the windscreen perhaps. Anyway will update this once I do more testing.

It should have an integral fan and a/c switch. The centre of the switch controls the fan speed, the outer of the switch controls the cooling temperature and when turned to zero it cuts out the clutch.

If you have both the heater and airconditioner on, when the engine is warm, the heater will win anyway. It's sometimes good to use them both because the airconditioner dries out the air which helps with defogging the windows.

 

[jblueridge]

. It's sometimes good to use them both because the airconditioner dries out the air which helps with defogging the windows.

Also running ac in winter keeps o rings in system from drying out.