How to tell if an electric fan clutch is working right?

[belfert]

How do I know if my electric fan clutch is working right?  I'm not 100% convinced yet my cooling problems are fixed and MCI says the clutch is the most common failure they see on a Dina.

But, MCI can't tell me if the Dina has a single speed or dual speed electric clutch.  (MCI stocks replacement clutches so you would think they know what they sell.)  A two speed fan clutch goes to more cooling upon command from the DDEC when a certain temp is met.

My fan freewheels when the ignition is off, but it locks up right away if the ignition is in the run position even without the motor running.  No idea if this normal or not.

I'm still not convinced on the overheating since I gain up to 5 degrees on the relatively short grades locally.  I do need to run the infrared thermometer over the radiator to see if it is cooling properly.

[tekebird]

I think with the series 60 5 degrees on a short grade is not acceptable.


I don;t have that gain on a 5 mile 6% grade with my 2 stroke

[Sammy]

Brian, you need to look at a schematic diagram of the electrical circuit that controls the fan clutch.
This will tell you if it's a one or two speed fan clutch, and will tell you how it is controlled.Is it air operated? Is it an electromagnetic style clutch?
I have never wrenched on a Dina, but the fleet of Prevost H3's and XLII's that I ran had a 2 speed electromagnetic fan clutch. DDEC would control both speeds based on the coolant temp reading it "saw".
I was able to "force" an output from DDEC with the diagnostic tools I have - master switch "on", engine not running, then telling DDEC to activate the fan clutch and physically grabbing the fan to see what was going on. Send me a copy of the schematic if you need help. 

[belfert]

I know the fan clutch is working at low speed as it locks up when the ignition is on.  The question is if it switches to high speed at any point.

MCI's idea is to block the radiator, start the coach, and then wait until temps get up and see if the fan kicks into higher RPMs when the temps rise.  I'm not certain I want to do this, but I guess it wouldn't hurt the engine as long as the temp doesn't get too high.

I don't want to keep throwing parts at my cooling problems if I'm not sure that part is the issue.  A big issue for me is running out of time.  I need to be ready to roll on September 25th for a 4,000 mile trip including crossing the rockies.  I only have four full weekends free to get the bus ready and I have a LOT of work to do besides this overheating issue.

[Sammy]

You need to determine if the fan clutch is controlled by DDEC. The DDEC ECM should control a relay, which then activates the fan clutch. My coaches had 2 relays - 1 for low speed, 1 for hi speed.
You will be there all day with a piece of cardboard,engine running, to try to get it to approx 205 degrees.
IF it is controlled by DDEC, take it to someone with diagnostic tools - software or a ProLink- they can force the fan control output from DDEC for you. 

[belfert]

I've pored over my pages of electrical schematics and indeed the DDEC does control a relay for the fan clutch.

The issue is the fan clutch only shows a ground and positive going to it so I assume it is single speed on or off.  I'm not sure why they have a clutch if the fan is always on anyhow.  I need to call MCI again and talk to one of the Dina engineers they have on staff.

[belfert]

Okay, I talked to MCI tech support again.  They confirmed the fan clutch is single speed on or off.  The fan clutch should be not be engaging at temps less than 190.

My clutch seems to engage 100% of the time so the relay could be bad.  It appears the fan clutch is NOT an issue for my cooling problems since it is engaging unless the clutch is slipping internally.

[dickegler]

Hi Brian,

Here's an off the wall thought.  Any chance the relay was miswired NC instead of NO.  The fan would run all the time, until 190, then turn off, just when you need it?

I know it's a long shot, just something else to check

dick egler

[belfert]

Checking the relay is next on my list.  I probably won't get to it until Sunday as I am booked up until then with non-bus stuff.  I'm not going to worry too much about fixing it right away if the relay is stuck on.  I would think it would take a long time to get to temp with the fan on all the time, but after thermostats and radiator cap it seems to come to temp much faster now.

I would be suprised if the fan is shutting down at high temps.  I would think my bus would overheat like crazy even on flat land.

[Hi yo silver]

Brian,
I had the same thought; I think the bus would heat quickly, on flat land if the fan wasn't running.
Dennis

[Busted Knuckle]

Brian,
I'd bet that the PO has wired it so that the fan is on ALL the time! I've seen it many times where someone thinks the system is not working so they just hot wire it to permantly come on when the switch is on! FWIW!
  BK 

[belfert]

Brian,
I'd bet that the PO has wired it so that the fan is on ALL the time! I've seen it many times where someone thinks the system is not working so they just hot wire it to permantly come on when the switch is on! FWIW!

I think that is much more likely than it turning off at 190.  If it is the case that it has been wired to be on all the time I'll just put it on the bottom of my to-do list.  It really doesn't hurt much since I rarely drive iit n the winter.