No power to truck Battery Cables?

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Jbone36, Nov 11, 2018.

  1. Jbone36

    Jbone36 Registered User

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    No power to cab fuses are good..please see vid thanks
     
  2. Jbone36

    Jbone36 Registered User

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    seriously tho do these cables go to the glow plug wiring harness?
     
  3. franklin2

    franklin2 Full Access Member

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    I tried to look for it in the video, but you never really go over in that area. And I do not know what year you are working on, but most of these trucks had a starter solenoid mounted on the pass side fender, just like a gas truck. One of the main purposes of this solenoid on the diesel was a point to distribute all the power to the glowplugs and the cab ignition switch and fuse box feeds. And they did use the solenoid to trigger a small wire to send voltage to the solenoid on the starter.

    If I were you, I would get me a small 10 amp battery charger. These have circuit breakers built into them, if there is a mistake or a problem somewhere, the circuit breaker will trip instead of smoking any wiring.

    I would then look to see if you do have a starter relay/solenoid mounted on the pass side fender. If you do, you should have tons of smaller wires with fusible links going to it. These are all your power feeds for various parts of the truck. And then you should have a medium sized red wire that goes to the battery power. I would hook the battery charger to the post with all the little wires and see what you get. The battery charger should be large enough to work most things in the truck, just not the starter.
     
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  4. woodstock

    woodstock Registered User

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    The ambulance uses a master kill switch in the cab so the batteries wont die if an accessory is left on when parked . If this switch is in the off position you won't have power to the cables.
    Also an ambulance has a battery isolator on the firewall that isolates battery 1 from battery 2 . This isolator has a diode built in it that acts like a 1 way door . If this battery isolator is bad like maybe an open circuit in the diode it will kill the power to the cables. Battery isolators go bad fairly often. I hope this helps. Good luck
     
  5. woodstock

    woodstock Registered User

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    Also note that the battery cables go to the isolator first . Then from one side of the isolator to battery number1. Then from the otherside of the isolator to battery number 2. So say in revers the batteries go to the isolator first then to the truck wiring or main battery switch then into the truck cab . This is a short version of explanation as to the path of voltage . Ive owned 3 ambulances that had 7.3 idi motors. You could look up onlne for a diagram of how to wire a battery isolator and that should explain. There are shorter battery cables that run from the isolator to each battery . For example if the isolator has 3 studs on it 'lets call them studs A B & C. Then positive cable from battery number 1 would connect to isolator stud A. Positive cable from battery number 2 would go to isolator stud C and the positive from the alternator would go to isolator stud B thats normally the middle stud on the isolator .
    Now isolator wiring varies and my explanations may differ so I would again recomend you looking up examples of how battery isolators are wired. The isolator is there to isolate battery number 1 from battery number 2 .
    Example if battery number 1 went dead' battery number 2 would still be charged because they are isolated from one another. If there was no isolator or the isolater internal diodes shorted out then a dead battery number 1 would inturn discharge battery number 2 to the same discharged level as battery number 1 because the batterys would not be isolater from one another. Good luck and I hope this helps resolve your problem
     
  6. Jbone36

    Jbone36 Registered User

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    I appreciate all of the comments and help,and apologize for delay in response.."got injured and forgot I even had an ambulance " I'm recovering and hoping to get back to it soon.
    But anyway I never saw any solenoid on the fire wall although it could be hidden. There is quite possibly a breaker tripped somewhere as the ambulance has tons of wires and breakers but I'm just stumped on where that red wire goes?. And yes behind the seat there is a switch says on off but doesn't seem to make a difference. I'm assuming because that red wire or others aren't hooked up. I'll do some more hunting and troubleshooting when im back in service and get back with yall. BTW it's a 1992 super duty..thanks again
     
  7. franklin2

    franklin2 Full Access Member

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    The solenoid (really it's called the starter relay) I was talking about should be mounted over on the passenger side inner fender. It would be very unusual for it not to have one.
     

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