Cooling Fan (1 Viewer)

[777sam]

I’ve checked all of the continuity going to the Cooling Fan Control Timer as well as the wires going to the fan. Fan motor checks good.

Q1…If I want to send a signal to the Control Timer from the manifold temp. sensor, would I intentionally ground the wire or disconnect it?

Q2…If the Manifold Temperature Sensor indicates to the Control Timer that it is hot, should the fan turn on when the ignition is turned off or does it require the engine to be run for a minimum amount of time?

Thanks very much for your help!
Sam

 

[45Dougal]

1- I think you ground it to switch on the fan. You won't hurt it by doing so.

2- isn't the point of the timer to keep it running after the engine switches off?

 

[777sam]

1- I think you ground it to switch on the fan. You won't hurt it by doing so.

2- isn't the point of the timer to keep it running after the engine switches off?

Yes it should turn on after the engine is shut down. I was just wondering what parameters needed to be met: engine shut down, engine manifold hot, etc…? Im not sure if my temperature sensor is working properly or i have a bad Cooling Fan Control Timer? I have about 3 controllers, none of which seem to work.

 

[3_puppies]

if the wire on the temp sender on the manifold is grounded, everytime the engine is shut off the fan should run, whether the engine is hot or not.

 

[45Dougal]

Sounds like a bad timer - have you tried opening one up?

 

[doseman]

There is a relay that is associated with it too. That was my issue after installing the controller-after refurb. I sent my controller to Engineer8000 here on Mud. He cleaned it, reflowed the solder joints and bench tested it. Worked perfect. When I installed it, I thought I would be proactive and install a new relay. Relay was bad so I put the 45 year old one back in and working as it should. There is also an inline fuse under the dash. If it is blown, it will not turn the fan on.

I did ground my temperature wire, so it runs every time I turn the ignition off.

 

[777sam]

Sounds like a bad timer - have you tried opening one up?

There is a relay that is associated with it too. That was my issue after installing the controller-after refurb. I sent my controller to Engineer8000 here on Mud. He cleaned it, reflowed the solder joints and bench tested it. Worked perfect. When I installed it, I thought I would be proactive and install a new relay. Relay was bad so I put the 45 year old one back in and working as it should. There is also an inline fuse under the dash. If it is blown, it will not turn the fan on.

I did ground my temperature wire, so it runs every time I turn the ignition off.

Where is the relay located? I installed a new fuse.

 

[doseman]

Mines a ‘79, not sure what year they changed set up. Its right next to the controller

 

[doseman]

Another

 

[777sam]

Another

View attachment 3756372

My 1978 must be a bit different.

 

[TheHardWay]

For the 78,the relay is inside the case:

 

[777sam]

Inside the plastic case? Is it possible to replace it? Test it?

 

[45Dougal]

For the 78,the relay is inside the case:

View attachment 3756567

I don't see anything obviously burnt. The diodes all look like they've seen some heat, but nothing catastrophic.
How does it smell?
Let's see the other side?

 

[TheHardWay]

Inside the plastic case? Is it possible to replace it? Test it?

Inside the plastic case, yeah. It is testable, but I sent mine to @Engineer8000 to make sure it was working as it should. He replaced the timing capacitor and two diodes and it's good as new!

 

[TheHardWay]

As requested by @45Dougal :

This was in good condition, no smell.

 

[Engineer8000]

The 78 carb cooling fan controllers are problematic. I have repaired several. The relays are probably fine. I posted a video how to test the 78 controller previously. The controller is "armed" when the ignition is turned on. The fan will cycle with temperature while the ignition is on, then it will continue to cycle with temperature for 20-30 minutes after the ignition is turned off. Grounding the lead to the sensor tells the controller the temperature is high.

post 166

Cape Fear Electronics

connectors

forum.ih8mud.com

 

[45Dougal]

It looks like this one has already been re-soldered on a few components, so I guess they've had problems with it in the past.
I'm curious what the cause of failure is with these, because they look pretty simple; are the diodes just not up to the job?

 

[777sam]

Inside the plastic case, yeah. It is testable, but I sent mine to @Engineer8000 to make sure it was working as it should. He replaced the timing capacitor and two diodes and it's good as new!

How much$

The 78 carb cooling fan controllers are problematic. I have repaired several. The relays are probably fine. I posted a video how to test the 78 controller previously. The controller is "armed" when the ignition is turned on. The fan will cycle with temperature while the ignition is on, then it will continue to cycle with temperature for 20-30 minutes after the ignition is turned off. Grounding the lead to the sensor tells the controller the temperature is high.

post 166

Cape Fear Electronics

connectors

forum.ih8mud.com

How do these look? If issues, are they repairable?

 

[fjc-man]

The solder joints for the backside of the plug might need a redo.

 

[45Dougal]

They all show signs of localised heat stress and historical repairs.
Sounds like @Engineer8000 is your easy option.

If you're counting the pennies, and have the tools, then strip one down for parts and draw out a circuit diagram for it in the process.