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1986 f350 w 6.9

Discussion in 'Ford Trucks' started by fronig, Jan 26, 2004.

  1. fronig

    fronig Junior Member
    from CT
    Messages: 6

    ok, i have an 86 f350 with the 6.9 in it. it has 2 875cca interstate batteries(1.5 years old about). and a brand new bigger alternator. i use a 7.5 fisher mm on it and the plow moves slow. the lights do not dim for a while but after a while the lights dim and the plow gets really slow to the point that there is not enough power to move the plow at ALL. what is my problem and what do i need to do. there is new atf fluid in the pump and it is full. i have adjusted the "plow lowering" so that it should drop and go up fast. but it did nothing at all. i called a fisher dealer near me and they said it is the little hyd. pump inside that costs only 140 bucks. and when i replace that the plow will move fast, like it should. but, my question is the power issue. the last storm i went to fill up after a while and i turned the truck off and it would not start after i filled up, i had to jump it. i really need some help. a storm is comming tommorrow and i need to know what i should do. do i risk damaging the pump or alternator if i plow with it like this???

    sorry this was long, thanks in advance!!

  2. crashz

    crashz Senior Member
    Messages: 256

    Bigger alternator? How much? You may be just draining your system faster than the recharge. Is your volt gauge working? Going down at all?

    My fathers old 86 would do the same thing after about 6 hrs of plowing. That would be the time we would go to breakfast or lunch and let the truck idle in the parking lot. Between the driving and idling, it would recharge those batteries enough for a few more hours of plowing. All of our electric/hydraulic plows do that.

    You may want to upgrade your alternator. But first, go throught the truck and look for corroded wires and grounds. Make sure you utilize all of the avaible current you already have. All of that current draw with the plow and lights and such need extra heavy duty connections.
  3. Tediesel

    Tediesel Member
    Messages: 46

    If you let the truck sit overnight can you start it?
    This just happened to my '83 6.9 It was the voltage regulator draining the batteries.
    According to my handy dandy paper I got with my new alternator that I didn't need, the alternator will only put out 60 amps at redline (3300ish). When your plowing you probobly see 2000 on average and then its putting out about 35. Thats enough for every day driving but not too impressive.

    On my old plow jeep It does the same thing, Run it and its fine but if I'm working in a tight area with the lights on and a lot of angling and up and down it drains it dead.
  4. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    Make sure the batteries are topped off with distilled water. Check and Clean ALL connections,the engine and frame has a bunch of ground points do those too. Put dielectric grease on all the connection's to protect them from water and crud.Charge both batteries up and have the charging system checked. A place like Autozone or Advanced will check it for free. They can tell you if alternator is putting out what it should and at what RPM. Some batteries will die quick when they are used in a plow truck. The more you paid for them the longer they last.Try to plow with the least amp draw you can. If the lot is lighted I will just plow with the amber beacon light going. An automotive electrical shop can upgrade your alternator to a bigger output for you. Your alternator may just be getting tired too, with the truck being a bit older then most. Your pump may need the filter screens cleaned if it has them. Have an extra ignition key made, I always leave my truck run with the doors locked when I fuel up. Never know the starter could pick now to die too.
    Last edited: Feb 6, 2004