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Old 10-15-2021, 09:31 AM   #1
Mini-Skoolie
 
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Year: 2001
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Engine: T444E
Wiring of Horton Electric Clutch: A story and a request

The bus started overheating this summer, but didn't when it was in WA. I think it hates CA...

I drove it up to Oregon, and it ran high temps with stops to let it cool down. I first marked it up to 100' days. Then drove around Oregon for a week with no issues. Came back to CA, and 100' days and again overheating. Seemed to be getting worse, so limped it home and thought it may be the fan clutch.

Now, I've been educated on electric fan clutches (mainly, it spins freely with no power...that doesn't mean it is bad). NOTE #1: Test the minor stuff FIRST

So, thanks to a conversation with ISAF2009, I went to work on the wiring.
NOTE #2: Ask for help.

Is the relay for the electric fan supposed to be wired in reverse? When the ignition is turned on, bus not running: Relay has power through it, circuit is closed, fan clutch off.

It seems that when the relay is interrupted, that's when the fan clutch engages. The relay is normally closed, and when I open the relay, THAT's when the fan clutch engages. This seems backwards, but that is how this is running right now.

It makes me think that this has been wrong since the day I got it, but since it was a WA bus, no one ever noticed, as it doesn't get to 100' days up there.

I was thinking that I can just wire up a relay at the booster pump and manually control it from the front of the bus, as the switch is already there and working. However, referring back to Note #2, I figured I would ask first.

Thoughts/advice?
Thanks!

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Old 10-15-2021, 10:12 AM   #2
Bus Crazy
 
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I am not very experienced with the electric fan clutches...but on our Freightliner, the fan clutch needs power to engage/lock and spin the fan. I don't know if this is the norm, though. I will say that I think your description of operation would be a better system...since it's probably better to have the clutch fail in the "cool off the engine" mode if you lost a wire. In our Freightliner, when the wiring got torn free that meant we also lost fan cooling.
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Old 10-15-2021, 10:53 AM   #3
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What clutch do you have? That will determine the operation.

If it's an electro-magnetic unit, providing power to the coil locks the clutch, remove power and it's free.

Electro-viscous units typically operate in the same way, as in power applied locks, remove power and they're free. But these units are typically pwm controlled, to vary the level of engagement of the clutch.

I can see how an electro-viscous unit could very easily be designed in a way that would disengage with power applied, as it's nothing more then a pin being moved to flow or block fluid, but I've never come across one that operated that way.

Most spdt relays have a NC and NO pole that will latch to the #30 terminal depending on if the coil is or isn't energized. Where your fan terminal is at and when the coil has power will determine if the clutch is supposed to have or not have power.

I'm not sure if I've ever seen a t444e with an electric fan clutch, the ones I've worked on were all viscous.
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Old 10-15-2021, 09:31 PM   #4
Mini-Skoolie
 
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@Rossvtaylor:
"...since it's probably better to have the clutch fail in the "cool off the engine" mode if you lost a wire."

I thought of that also. Figuring it as a fail safe, but then the engine may never heat up either...better than overheating I think.
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Old 10-15-2021, 09:33 PM   #5
Mini-Skoolie
 
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@Booyah45828

It's a Horton Electronic clutch. Not viscous, but straight electrical. I am able to get it to clamp when interrupting the relay power. Thank you!
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Old 10-16-2021, 01:54 AM   #6
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i got nothing.

but i did replace my horton clutch once with a new one.

the clutch wires will work either way, there is not a polarity to them.

on my cummins, the fan clutch wire is hot all the time. it comes from its power source, goes to a thermostat switch, then the fan, then back to ground.

your fan has to have power when temps get hot....~200..... ussually they're like on at 210/off at 200... something like that.

what would be triggering your relay to turn the fan on and off? a tstat?

with my past experience trying to wire an electric fan to assist cooling, i'd say, don't waste your time making in cab switches. just fix it right and the system will work.

good luck
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Old 10-18-2021, 09:12 AM   #7
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Quote:
Originally Posted by AdamKnox View Post
@Booyah45828

It's a Horton Electronic clutch. Not viscous, but straight electrical. I am able to get it to clamp when interrupting the relay power. Thank you!

Electro mag then?

Electro mag units operate opposite of what you're describing, as in removing power disengages the clutch. It's no more then a magnetic coil, so as turf said, it's not polarity specific. Remove power or ground and the clutch is off.

IDK what relay you're pulling or how it's wired. But removing power from an electro-magnetic clutch disengages the clutch 100% of the time. Instead of messing with the relay, pull the clutch connector and see what it does.
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Old 10-24-2021, 11:15 AM   #8
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Update: Went through and checked current again. Tested electrical and mechanical. Added a new separately wired relay and switch to the set up mentioned above so I can manually turn on the fan.

So... Start with the simple.

It didn't work. Went back and checked electrical again, it wasn't obvious still, but I went with what made sense at this point. I swapped out the relay with a known good one ($20). Viola!

I can now manually turn on the fan with the switch from the front of the bus. I haven't gotten it hot enough to see if it will turn on based on thermostat temp yet, but I'm planning a trip soon to test it out. For now, I can hear and feel the difference when the fan is on in the bus/engine.

It is definitely wired in "reverse", so I expect this burns out relays sooner than later. The other two relays in the electrical box (RE bus) look original. This one was replaced previously based on the look of it. That seems to be the issue.

SO...rambling aside, I hope this helps someone in the future.

Cheers all, and thanks for the direct messages and public replies! Keeping this community great!
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Old 10-25-2021, 06:18 PM   #9
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good luck on your repair!

the few times ive done similar - bypass the truck system - it always comes around to bite me.

i removed my fan cooling switch because i kept killing my battery.
it worked fine, but i'd forget it was on, stop at walmart and return to a dead vehicle. the 2nd time it stranded me, that bypass switch came out.

good luck
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