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MM1 Problems

Discussion in 'Fisher Engineering Discussion' started by mayhem, Feb 20, 2008.

  1. mayhem

    mayhem PlowSite.com Addict
    from Peru MA
    Messages: 1,016

    8' MM1 HD blade, 3 wire insta-act system with Fish Stik controller mounted on a 2000 Chevy 3/4 ton. I installed this plow used in fall of 2006 and its worked perfectly since I put it on. Got about 5-6" last night so I went to plow the drive this morning, got the plow on, wires hooked up, powered on the controller and the thing wouldn't lift. I can hear the motor working (or at least the relays kicking on), the triangle on the top of the lift piston even shudders a bit...but it won't go up. Tested the angles and it only turns to the right(in other words the driver's side piston moves out), but it won't return to center. Popped it off and came into work, but I need to get it fixed ASAP or I'm stuck shoveling.

    I have done no diagnostics at this point, so I'm looking for suggestions. My firs tthought is air in the hydraulics so I can certainly check the fluid level when I get home, next thought is possibly a frayed wire in the controls coming from the truck, but I would tend to think that if that were the case I would not hear anything when I hit the lift button on the controller. Also considered I might have some blockage in the lines, but it seems odd that it would do both of them at the same time.

    Wasn't particularly cold last night...temp readout on the truck said 13 this morning, I've used it well below zero without any issues before.

    Resivoir is filled with ATF by the way...its my understanding that this should be ok, but that my real risk is possible reduced or no performance in extreme cold (like 20-30 below). Maybe I need to bleed it out and top off?

    I remember alot of peolpe telling me the coils tend to blow, but I'm not sure what the behavior is when it does...would it just shut the whole thing off or does it blow in smaller stages like the heater blower motor resistor?

    Thanks in advance.
     
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Sounds like the S3 valve isn't opening for one reason or another.

    Start with checking the S3 for magnetism at the coil with the controller in the raise or angle left function. That will separate it from either an electrical or hydraulic problem making it much easier to pinpoint the problem. Then go from there.
     
  3. mayhem

    mayhem PlowSite.com Addict
    from Peru MA
    Messages: 1,016

    Where is the S3 valve located on the coil and is there a recommended test procedure? I'm downloading what I think is the corect manual from Fisher rihgt now, so hopefully this will be clearer to me.

    Should I purchase a replacement/spare coil today just in case I need to? If I understand correctly this is a wear and tear part and it might be a good idea to keep a spare on hand. Fisher dealer is 30 minutes from work, but an hour from home.
     
  4. Flipper

    Flipper PlowSite.com Addict
    from CT
    Messages: 1,180

    The shuddering makes me think it could be frozen up. The ATF would be fne but if it got any moisture in it the blockage will often occur at the smallest point and that is around the coils. The coils are under the plastic cover where the angling hoses come off the power pack.

    Make sure all the wires are connected at the grille and under the coil cover. Press up on the control and see if a screwdriver is attracted to the coil, meaning it is getting magnetized. If so if may be blocked.

    If you think is could be wiring you could jump the coil wires with 12 volts off the battery. and the use the controller to activate the hi amp lead for the pump motor. This is often done for testing.
     
  5. mayhem

    mayhem PlowSite.com Addict
    from Peru MA
    Messages: 1,016

    OK, so I got everything apart and here is what I found:

    S3 coil never magentizes, regardless of controller setting. S2 and S1 do magnetize at the proper controller settings though. I OHMed out the S3 coil and got 7ohms which the manual indicates is proper...so I've either got a bad S3 solenoid (or blocked solenoid), a wiring problem (broken wire) or something else completely that I'm not thinking of.

    I took the whole S3 assembly out so I can clean and inspect it for crud or metal filings to see if its blocked and I'm going to go jumper the S3 hot lead onto the S2 coil, whihc will either energize the coil when I lift, which will confirm I've got good wiring, or it won't energize in whihc case I think I might have a wiring problem. I can then reassemble S3 and run it off the S2 wires, which could at least confirm my coil and solenoid are good.

    Suggestions are always weclome...its cold out there!
     
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Your on the right track so far..if you jumper the S2 & S3 together and it angles left instead of raising you'll know for sure the valve/coil are good and that the valve and the passages in the manifold are clear (not frozen). That would identify it as a 100% wiring issue.
     
  7. Flipper

    Flipper PlowSite.com Addict
    from CT
    Messages: 1,180

    Yeah. That really makes me think it is wiring. Check the pins in the grille connector. The manual should say what pin it is. I can never remember them and don't have my books here. Then using a meter you can check from pin to powerpack on the plow side and from pin to iso module on the truck side. Also visually inspect the pins. You can spread them apart a bit so they fit tighter in the socket.
     
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Pin # 4 for the S3.

    Top row, 4th from the left if the alignment tab is to the top. :)
     
  9. mayhem

    mayhem PlowSite.com Addict
    from Peru MA
    Messages: 1,016

    Think I found it. Wire to S3 broke right off at the edge of the truck side harness that runs from the cab controller. I jumpered it around the harness and got magnetism at the S3 coil, reassembled everything and remounted the plow to the truck...naturally it didn't work, but I think my jumper broke. I'll try jumpering the two coils together tomorrow to make sure I don't have two problems and then run to town and pick up a new controller harness.

    Thanks for the help guys.
     
  10. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Would surely be a likely candidate...keep us posted.
     
  11. mayhem

    mayhem PlowSite.com Addict
    from Peru MA
    Messages: 1,016

    Finally finished.

    It was, in fact, the broken wire. I tried last night to bypass the truckside harness and got it to magnetize, but when I broke the connection, reassembeld the grille and plow and mounted everything back up to the truck I broke the connection and was unable to get it back together.

    This morning with a few hours sleep under my belt I opted instead to just bypass the harnesses completely. I ran a medium gauge power wire (like for a small subwoofer amp) direct to the S3 coil hot lead and wire-nutted it to the original bypass wire I started last night. Sucker fired right up no problems.

    I'll put some quick release clips on it later this weekend and buy the replacement truckside harness when I have the opportunity so i can either wait till warmer weather to change it out or at least have it on hand if my repairs break loose.

    Again, thanks to all for their advice.
     
  12. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Those broken wires will get you every time... Good to hear you got it figured out.

    My favorite one are when they break internally without breaking the insulation, and just enough to pass enough current to test good but wont carry enough current to actually power the coil..