Carb fan.... is it working?

[FJ60BigLou]

Before I get the obvious response, I know if it blows it's working.... if it doesn't it's not. But I also know its on a thermo sensor and it runs after ignition is off and when the sensor says it's too hot. I've had the truck (85 FJ60) for about a month and I haven't heard the fan run since I've had the truck. We are just starting to see warm weather in Louisville, so the engine may not have gotten hot enough to trip the sensor. The longest I have driven it so far is about 30 to 45 minutes, so again the engine may nit have gotten warm enough. The PO said the carb fan is operating. With all that said I am taking my daughter on a 2 hour trip next week and we're taking the FJ. I don't want to get on the road and find myself with vapor lock. Is there a way to test the carb fan and thermo sensor before we hit the road???

 

[Trapper50cal]

That's more than enough time for it to turn on after turning off the engine...when mine is half way to operating temp (a run to the gas station) it still flicks on and off like it can't decide. It should be turning on under the conditions you describe. Look into grounding it so that it just automatically does 15min each time.

 

[Slow Left]

Have you checked the fuse? It should be on the same fuse circuit as the Dome light (cabin light up front).

 

[Spike Strip]

If the wire is still connected to the sensor, just disconnect the big green connector and use a jumper to ground the fan side of the wire. Cycle the ign key on/off. If the blower is working it will blow.

 

[Callahan Offroad]

Mine would blow after shut-off every time my truck hit operating temp.

 

[FJ60BigLou]

Thanks for all the advice -- you guys are great! The fuse was blown. I put a new one in, drove around, and when I turned it off it was humming perfectly. New question: what would make the fuse blow in the first place? Do they just get old? Is there a bigger issue?

 

[Trapper50cal]

A good test to answer that is going to be the longevity of the new fuse you put in....It could have just been that fuse's time....they get old.

 

[SteveH]

I'll tack this onto an existing thread. My FJ62 carb fan works if you ground the sensor wire with the ign. on. Otherwise, I've never heard it work, even on blistering hot days.

I took the sensor out, and it showed infinite resistance. I heated it with a torch (gently) and the resistance started at 800 ohms and dropped to 200, before I chickened out and remove the torch. Is this normal? I don't know if the sensor is suppose to switch hard to zero ohms at a certain temperature, or if the resistance profile I saw (while heating) was normal. Does anyone know how a working sensor tests out? thanks!

 

[TheJackRabbit]

Before I get the obvious response, I know if it blows it's working.... if it doesn't it's not. But I also know its on a thermo sensor and it runs after ignition is off and when the sensor says it's too hot. I've had the truck (85 FJ60) for about a month and I haven't heard the fan run since I've had the truck. We are just starting to see warm weather in Louisville, so the engine may not have gotten hot enough to trip the sensor. The longest I have driven it so far is about 30 to 45 minutes, so again the engine may nit have gotten warm enough. The PO said the carb fan is operating. With all that said I am taking my daughter on a 2 hour trip next week and we're taking the FJ. I don't want to get on the road and find myself with vapor lock. Is there a way to test the carb fan and thermo sensor before we hit the road???

Mine quit working years ago, so I just grounded it and have the 15 minute cooling regardless of operating temperature. During winter I disconnect the ground lead.

 

[Slow Left]

I'll tack this onto an existing thread. My FJ62 carb fan works if you ground the sensor wire with the ign. on. Otherwise, I've never heard it work, even on blistering hot days.

I took the sensor out, and it showed infinite resistance. I heated it with a torch (gently) and the resistance started at 800 ohms and dropped to 200, before I chickened out and remove the torch. Is this normal? I don't know if the sensor is suppose to switch hard to zero ohms at a certain temperature, or if the resistance profile I saw (while heating) was normal. Does anyone know how a working sensor tests out? thanks!

I couldn't find the Electric Cooling Fan circuit in the wiring diagram from the "Landcruiser chassis-body-84-90 Repair Manual" (which includes the USA FJ62 model), but I found it on the FJ60 USA wiring diagram (see image below).

Don't know if it is the same.

Do you have an image of the FJ62 USA circuit?

Either way, your testing supports my interpretation of how the sensor should work when it is working properly and seems to support the logic of the mod whereby the wire that connects to the sensor is detached from the sensor and grounded (and as a result, the fan turns on after each shut down of the engine).

The reason why I think your tests show that the sensor is working correctly is that when the material inside the sensor is cold, the circuit is open (not grounded) and you read a resistance is very high - infinity - (open circuit).
And when you heat the material inside the sensor, the resistance begins to fall towards 0 and the circuit begins to close (in this case, when the circuit is closed, then it makes a ground - see wiring diagram).

Which means that by doing the mod, you are essentially mimicking the closing (grounding) of the circuit when the sensor is hot.

But if your sensor is working correctly, as your tests indicate that it is, and your circuit is set up as shown in the factory wiring diagram, and your electric cooling fan is still not working correctly, then there must be another problem in the circuit. Fuse? Relay??

 

[Slow Left]

I'll tack this onto an existing thread. My FJ62 carb fan works if you ground the sensor wire with the ign. on. Otherwise, I've never heard it work, even on blistering hot days.

I took the sensor out, and it showed infinite resistance. I heated it with a torch (gently) and the resistance started at 800 ohms and dropped to 200, before I chickened out and remove the torch. Is this normal? I don't know if the sensor is suppose to switch hard to zero ohms at a certain temperature, or if the resistance profile I saw (while heating) was normal. Does anyone know how a working sensor tests out? thanks!

Steve,

I located where the relay and 'computer' are for the cooling fan, in case that might help you.

 

[SteveH]

Slowleft - thank you - that give me more to work with in troubleshooting this.

 

[Slow Left]

Slowleft - thank you - that give me more to work with in troubleshooting this.

For what it's worth, your tests on the temperature sensor lead me to believe that it is working correctly (both the tests and the logic of the 'ground mod' given the wiring of the circuit).

Double check the FSMs to see if there is a test for the Cooling Fan Relay.

For the Cooling Fan 'Computer' you might be able to do a visual inspection to see if any of the solder has run or the lines are broken. You can also test the circuits on the computer for continuity because it is rather easy to identify components (resistors etc) on the board itself (1980s technology...HUGE components) and then follow the logic of the circuit - like is the path to ground continuous, etc.

 

[Slow Left]

My FJ62 carb fan works if you ground the sensor wire with the ign. on. .

Just to make sure I understand this correctly, does this mean that you only hear the carb fan working when the wire that runs to the temperature sensor is detached from the sensor, grounded, AND the key is in the ignition and turned to 'on' (whether the engine is running or not).

What about when the wire that runs to the temperature sensor is detached from the sensor, grounded, AND the ignition is off?

 

[SteveH]

After a year of driving, my EFI (Carb) fan finally came on while four-wheeling last weekend. It's a quiet little thing - it doesn't roar like the fan on my FJ40. So, if yours has never come on, it may just be that you haven't gotten the engine/underhood area hot enough.