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Thread: FMTV M1084, Marker Lamp Relay Gets Hot when I turn on lights.

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    Default FMTV M1084, Marker Lamp Relay Gets Hot when I turn on lights.

    Hello and thank you for the help.

    I am going through my 1084 after finally getting it to the house. Everything seems to be fine except the marker lamp relay gets hot when I turn on the lights.

    currently I only have two batteries hooked up to it (Wes, Simp5782 helped with the two battery hookup and he is very familiar with these) but my next step is getting two more batteries and seeing if that fixes the problem. Everything else seems to be working fine. The starter relay isn't kicking over either so it must be started by taking off the plastic cover to the relay and starting it by pushing on the relay. I have relays in route and hopefully a new relay fixes that problem.

    I know both issues are electrical so it's a possibility that the other batteries fix it. but it starts right up no problem with I push the starter relay. And it's hooked up in the 24 and 12 configuration with the two batteries that are in there.

    Any quick ideas before I dive off the cliff trying to troubleshoot this?

    Thanks again for your time and help.
    Last edited by BRob18E; 08-21-2019 at 15:05.

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    4 Star General NDT's Avatar
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    Replace it with a new one of the proper voltage and see what happens.

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    Do you think it would be ok to run it, I don't want to do more damage. Worst case scenario it just burns out the the relay?

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    Two batteries isn't your problem as lomg as they are connected correctly and the truck probably would not operate properly if they were not. I think quite a few of us run two batts...

    your problem is probably as mentioned, wrong voltage relay. That should be a 12V relay in that position, or it could be a 12V relay with a partially shorted coil...

    Probably best to simply bypass it till you get a replacement... EVERY lmtv owner should make up one or two jumper cables. Two 1/4 male spade connectors joined to the ends of a 2-3 piece of 12ga wire. Pull out the relay and install the jumper between pin 30 and 87 before driving...
    Last edited by Ronmar; 08-21-2019 at 19:17.

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    Thank you both for the support. So I have went out and switched around some of the relays (using the panel lid to verify the correct swap) and the relay didn't get hot. So I'm just going to replace All the relays since I plan on keeping this one. I had to good of an offer on my last M1083 to say no. Plus I've been waiting on this crane for a while.

    So, after playing the relay swap game, the starter still doesn't work with the push button. I have to open the relay and push it over to get the vehicle started. Thinking a bad relay, I swapped it out from two different positions (surprised me the horn and starter matched) and no luck on the starter button. Any ideas what to check next? I'm about to download the TM and start the troubleshooting procedures, but if anyone knows and can say, "it's probably this" then I would greatly appreciate it.

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    4 Star General NDT's Avatar
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    Most likely the transmission VIM may be the culprit. There are more relays and fuses inside there.

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    BRob18E (08-29-2019)

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    Thank you sir. I will get on that tomorrow morning as it's getting dark here.

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    Does the start relay chatter when you press the start button or nothing happens?

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    I believe NTD may of hit the nail on the head. I went to pick up the truck at Ft. Campbell because although it said it didn't run and wouldn't start, on the windshield it said "starts and runs" so I figured it was something simple. However MY DUMB @S$ didn't realize these trucks were 24 and 12 Volt so I may have done some damage to it hooking the two batteries up in series and giving it all 24 volts. That maybe why my 12 volt relays are getting a little warm now. (the light relay) But with that said, everything on the truck works great, even the CTIS is working perfect, which wasn't the case on my M1083. The way I had it hooked up it wouldn't power the gauges so I pulled the cover off the fuse and electrical tapped that relay so it would power the panel. Then we got it running by popping the cover off the relay for the starter and manually pushing it over. It started and ran but at that point the transmission shiftier would not power up. So I went home and had it shipped.

    I'm hoping NTD is correct and I have to reset some fuses or replace some relays in the VIM and it works great, but I may of done some more damage. But since everything runs, works at is should other than the starter, maybe I just reset or blown a relay. That's my hope.

    To answer your question, the relay does absolutely nothing when the starter button is pushed, but if I push the starter relay over to make contact, it fires right up and everything works perfectly.

    So if anyone after reading that may know of "Well dumb A@$, you definitely F'ed this up" I can greatly appreciate the straightforwardness and any criticism that is well deserved. I truly don't know how I owned one of these and didn't know it was both. My last one ran good other than a few things when I bought it, so I never dug into the electrical system. lol
    Last edited by BRob18E; 08-21-2019 at 23:33.

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    The trans will accept either 12 or 24V so you probably didn't kill anything. I would look to the circuit that powers the trans CB79 and there are fuses inside the Vehicle Interface Module(VIM). The start relay gets its power thru the VIM(neutral start safety) so the trans controller needs to be powered to close a relay contact inside the VIM when in neutral to provide that power to the start relay. The other side of the start relay coil passes thru the start inhibit/crank lockout relays to the pushbutton that when pushed completes a circuit to ground to energize the start relay...

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