Help Troubleshooting MCC Cruise Control

[ScottKY]

I have an '04 ST1300A that has the MCCruise electronic cruise control installed, which worked perfectly up until very recently. Now, however, it won't engage, and I'm having a hard time identifying the problem.

I had the rear wheel off recently for a tire change, and I thought maybe it was a problem with the speed sensor. But I ran through the speed sensor diagnostic routine per the MCCruise user's manual, and it appears to be ok. I also had the right side tupperware off recently to bleed the brakes, but I can't imagine what influence that might have.

I've run through a good portion of the diagnostics:

- Computer test ok (lights come on like they're supposed to)
- Vacuum test ok
- Switch test ok

Where I see the first problem with the diagnostic test is the step where you put it into diagnostic mode, start the engine, then press the SET and RES buttons, which is supposed to raise and lower the engine RPM. Nothing happens.

If I understand correctly, I think my next step is to check the voltage on the red wire at the connector that's inside the vacuum actuator unit. I haven't done that yet, because it looks to be quite a chore to get at the connector. I think I need to take the vacuum actuator off to disassemble it, and that looks a fairly involved process. I'll do it if I have to, but I thought I would solicit some experts before I dig into it.

Any ideas?

TIA,
Scott

 

[Uncle Phil]

Do you hear the actuator 'click' when you press the button? Check your wires on the sensor that they are making good connection. You do have to press the ACCEL button like a mad man to get the engine to pick up, then press DECEL quickly so you don't overrev the engine. My next thought would be the O-rings in the actuator as ethanol seems to be killing them. Do you have the clutch circuit and high rev circuit in place? If so, I'd bypass them just to eliminate two issues.

 

[ScottKY]

Uncle Phil, thanks for the reply. I did press the ACCEL button like a madman, to no avail. It has no effect on engine RPM whatsoever. I don't think the clutch circuit in place, as pulling in the clutch never did disengage the cruise. As for the high rev circuit....???? No idea. The cruise was installed on the bike when I bought it, so I don't really know for sure how things were wired up. I've been trying to work backwards from the installation manual to figure this thing out.

Forgive the potentially ignorant question, but how could ethanol gas damage the vacuum actuator? There's no fuel flow through there, right? Is it just the fumes and such?

The install manual keeps pointing me towards the "CIU", but I don't even know where that is located. I assume it's installed under the breather somewhere, but I haven't dug that far yet. I've been trying to work small to big, hoping it's something simple.

I'll check the connections on the speed sensor, but I don't think that where the problem is because the diagnostic speed sensor test checks ok.

Hopefully I 'll be able to dig into this weekend. Any additional suggestions would definitely be welcome.

Scott

 

[Uncle Phil]

CIU is CABLE INTERFACE UNIT - usually a black box with three cables into it - one from the actuator, one from the throttle, and one to the Fuel injector lever/(Carb bell crank for ST1100s). The ethanol fumes seem to destroy the O-rings (realize the actuator has a vacuum line from the bike vacuum system). On the ST1100s, there was a yellow (?) wire that ran to the coils to sense over revving of the engine. Don't know if it was on the ST1300s or not.

 

[ScottKY]

Well, oddly enough the cruise is working now. It's got me scratching my head though. I mentioned in my first post that I had the rear wheel off recently, and my first assumption when I discovered the cruise wasn't working was that the speed sensor got out of alignment. But when I'd did the diagnostic check, it passed. So I moved on. So last night, I loosened the axle bolt and fiddled with the speed sensor bracket, and I managed to get it a tad closer to the magnets in the rotor. Voil?, it's working now! So it was a problem with the speed sensor all along. Doh!

The odd thing is that the diagnostic check where you try to get the engine speed to change by pressing the ACCEL a and DEC buttons still doesn't do anything. Nada.

Oh well, it's working, so I'm gonna call it good.

Thanks for the suggestions and the information Uncle Phil.

Scott