fj40 carb cooling fan...do you run yours?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Testing the cooling fan

Best thread yet on cooling fan! Great info.
My temp sensor is mia but the green connector from from the wiring harness is hanging out in mid air. I have seen that grounding this connection should get the fan to run...no dice for me. How do I know if it is the fan motor or the fan relay mounted under the dash on oassenger side that is not working?
All fuses are good.

Any pics of the internals of the relay?
 
You should be able to jump the wires at the fan motor to the battery and run the fan, it is just a regular fan motor. Can't tell you the colors, but it is usually pretty obvious what is ground and hot.

Sometimes they get too much road spray and gunk in them. May have to clean it up to get it to work.
 
Rainflye40 said:
Best thread yet on cooling fan! Great info.
My temp sensor is mia but the green connector from from the wiring harness is hanging out in mid air. I have seen that grounding this connection should get the fan to run...no dice for me. How do I know if it is the fan motor or the fan relay mounted under the dash on oassenger side that is not working?
All fuses are good.

Any pics of the internals of the relay?
Click to expand...

I'd look at the cooling fan module. There's been issues with cold solder joints that might be your problem. When I took mine apart, that was the case along with some fried diodes I replaced with new ones from Radio Shack.
 
MoCoNative said:
You should be able to jump the wires at the fan motor to the battery and run the fan, it is just a regular fan motor. Can't tell you the colors, but it is usually pretty obvious what is ground and hot.
Click to expand...

Plus it doesn't matter. If you get them backwards, it will run backwards. It's maybe not great for the brushes to run it backwards for a long time, but for a go-no-go test it won't hurt it.
 
Take the cover off the module and apply 12V directly to the relay using the contacts on the back side of the board (the ones the little green wires go to). If the contact shuts then the problem is in the componets, diode, resistor or other. My relay didn't activate so I jumped it with a generic one from autozone still using the board so I would get the 20 minute fan run time.
 
Tagged for Reference
 
carb cooling

Thanks folks! Jumped the fan and it works fine. Removed the relay module, tapped on it a little plugged it back in, grounded the sensor connection and poof...fan works as advertised!

How do I check for cold solder joints and burned out stuff?
 
I checked my sensor with a lighter and a meter and it seems to work as it should. I used a power supply and applied 12v directly to the relay multiple times on the module curcuit board and it would not close. After jumping the relay with the one from Autozone I hit the old one again with 12V and it closed so I'm thinking the relay has in intermittent fault problem. The soldering is strong so you will need a soldering iron that gets good and hot. A cold solder joint might be pretty easy to see if you have good eyes and a bright light. The image is a sample and not the actual module board. If you know someone familiar with a meter they can check the resistors and diodes.
1solder.webp
 
Last edited:
Rainflye40 said:
How do I check for cold solder joints and burned out stuff?
Click to expand...

You might not be able to see the problem, but it won't hurt anything to reflow all the joints you can get to. I would think a cheapo soldering iron would be good enough.
 
I got mine to work last summer after reading about the reflowing here on IH8MUD. This fixed my hot start problems. Then last winter when it was 5 degrees outside the fan would run at shutdown and was able to fix this by replacing the three electroltic caps and cleaning the the trace side of the board. Now it has to be >75 for it to run.
 
I have a 78 and have been experiencing the same problem with the warm starts. For some reason the fan wires were cut by p.o. I am rewiring and am hopeful that this will solve the problem. Did anyone try to tell you it was the starter? Has fixing your fan helped at all with the floor getting so hot? Does the fan only run when you stop the engine or is there a sensor to switch on at a certain temp.?
 
This is great info. especially since I said:I wonder what that thing is, and I wonder where these wires go" But now I know. Not really warm right now here in the northwest, but I am going to look into the condition of mine to see if I can get it going just in case I need it.
 
imagirl said:
Has fixing your fan helped at all with the floor getting so hot? Does the fan only run when you stop the engine or is there a sensor to switch on at a certain temp.?
Click to expand...

It only runs when the engine is off and the sensor is hot. Mine will run at almost any ambient temp. I don't often drive it when it's freezing out, so I wouldn't know...
 
Where is the control box or module for this sensor ??
 
You must log in or register to reply here.

Similar threads

C
  • Question Question
What tools do you keep in your FJ40?
2 3
Replies
42
Views
4K
65swb45
65swb45
7
Cooling Fan
2
Replies
24
Views
2K
TheHardWay
TheHardWay
Mark Jennings
Do you service your Distributer
2
Replies
22
Views
2K
Pighead
Pighead
77ToyFJ40
1977 fj40 fan belt
Replies
1
Views
564
charliemeyer007
charliemeyer007

Users who are viewing this thread

Total: 1 (members: 0, guests: 1)

Share this page

Back
Top Bottom