1995 MCI 102D3 Cooling Fan Clutch Wirring Diagram

[NeoplanAN440]

Need some Help finding a wiring diagram or at least the main components that control the cooling fan clutch solenoid on my mci. the clutch is always engaged. 28v on skinner valve connector , but NO ground on second pin.  does the ground come from the temp switch or ecm
any help would be great !!!

[John316]

Neo,

Okay, this is a fun one. We have been through this several times. Couple of questions.

Do you understand how the system works, and how the solenoids are supposed to operate? Do you know that the fan clutch is designed to fail in the on position, as it currently has.

You are correct in the fact that you need ground for that to work. If it is the right side clutch, that would come from your ECM (for your charge air cooler too...but that is beside the point). When you say no ground on second pin, what does that mean? Are you testing the ground wire itself (stick a needle through the insulation and put your meter on that, to eliminate the connector)?

When we had that issue, it was just a matter of tracing that wire back to the ECM, double checking that was the one, and we simply spliced a new piece in. I cut it about six inches out from the ECM (again make sure you have the correct wire!) and I had ground. I didn't want to mess with replacing it to the wiring harness, so I used a quality splice to put the new wire in.

The connector end can be pretty tough, if you don't know how to work on them. That is an aircraft style connector. If you think that part is good, you might want to avoid that, also, and splice it just before the connector.

As a matter of course, those fans need to be oiled. The air filter and oiler is right underneath the solenoids, just to the left. That filter has to be kept clean and oiled, with a fine oil, to keep those fan clutches happy.

Hope that helps.

John

[NeoplanAN440]

Thanks John ,

yes i understand the basic function of the fan clutches , and i know how to work on the connectors. thats one good part i got from working on jets while in service. lol 

my problem was and is, that without a wiring diagram i cant tell if the wires for the clutch solenoid go through a junction box and some relays , or direct to the ecu.

as mentioned i have 28v on the solenoid connector , that come over the test switch.
so i was guessing that the ground is coming from the ecu or a relay that is activated by the ecu.

it looks like i will have to open the harness near the ecu and go by the wire number , and check if i get a signal there!!

[Oonrahnjay]

(snip) it looks like i will have to open the harness near the ecu and go by the wire number , and check if i get a signal there!! 

      Yeah.  That's one of the things that I have about "electronic" controls.  OK, if I have to have a ground at a connector terminal on a component to make the component work, and I check but don't see a ground, does that mean that the there is a wiring problem or and ECU problem (or both)?  So to really be sure, you've got to put the ECU in a state where it *does* show the ground (goes "low", as the "Sparkys" at Land Rover used to say) and then see if that ground is shown at the connector on the component.  And sometimes, getting the ECU to that state stably can be a PITA.   And then you have to figure out if the ECU is actually going to ground when it should during operation.  This stuff is complicated.

[John316]

Peter, sounds like you are way ahead of the average guy. That is really good. You are correct. Ground comes directly from the ECU (on our coach). MCI tech support told me that 9 times out of 10 it is a broken wire.

Jay, that is correct. You have to troubleshoot to establish whether it is a wiring or ECU problem. Usually it is wiring, but those ECU's can have trouble.

HTH

John