Another lmtv that won’t start

[ghog50cal]

i don’t have 24v at k1-86

 

[ghog50cal]

i don’t have 24v at k1-86

The trans panel is up with no codes and neutral neutral

 

[Ronmar]

The trans panel is up with no codes and neutral neutral

OK, good, we know you have main trans power thru CB79 otherwise the trans wouldn’t even light up, but the trans and VIM are fed from 3 places. Do you have 24V to/thru CB21? That is the power that feeds thru the neutral relay in the VIM. You also need to make sure that there is 12V getting to-thru CB35. That 12V is the VIM power. If you do, you will have to remove the passenger kickpanel to get under the passenger dash.

Mounted under the dash on the left is the black plastic watertight VIM module, with 2 electrical connectors. 24V from CB21 enters on connector PX33-F1 passes thru the neutral start relay contacts and comes back out on PX33-G1 and on to K1-86. Remove the box cover and you will find several relays. One of them is the neutral start relay you need to make sure it is working/energizing when the main switch is turned on. There are also a few fuses in there, one for the 24V from CB79 that powers the transmission and the other for the 12V from CB35 that powers the VIM relays. If it is missing, I don’t think the vim relays can energize. If the 12 and 24 are making it to the VIM fuses and the neutral relay contact I would pull the neutral relay and look to see if any power is on one of the coil terminals, or you could swap the relay with another one in there with the same p/n. Like the power panel, the VIM uses both 12 and 24v coil relays…

 

[ghog50cal]

Ok I have removed the kick panel both the red 10 amp fuses are good I’m not sure I swapped around the relays with no change to k1 not sure where too go from here really

 

[ghog50cal]

I’m not sure which ones px33-f1

 

[ghog50cal]

I’m not sure which ones px33-f1

I don’t think px33-f1 has any power

 

[MrMikey4026]

Ronmar
Any of this seem familiar?
Like the VIM I fought on Phil's truck!

 

[Ronmar]

I don’t think px33-f1 has any power

OK well I think PX33 is larger than the other connector. If you look inside the connector the pins should have small molded labels. F1 is the 24V in for the start circuit so if you are sure power is getting thru CB21, you can pull it out and either jumper across CB21 or insert a standard automotive blade fuse in it’s place To be sure.

That power goes to terminal board 1-36 which sends it out 1-34 and down to the VIM connector F1. TB1 along with TB2 are mounted under the power panel mount plate(bunch of Phillips head sheet-metal screws hold it in). That same power from that group on TB1 can also be seen over on the frequency divider box Under the drivers dash. If you open the drivers door and look up under the dash left of the steering colunm there is a little box(about 1-1/2 x 2”) with some colored wires on it. It has a 6 pin connector and that same CB21 power is sent to pin 3 on that connector…

If the trans is controlling the neutral start relay(NS) in the VIM CORRECTLY, You should be able to feel it click with your fingers when the main switch is turned on…

 

[ghog50cal]

well everything is checking out good on it but still no starter button function

 

[Ronmar]

Well if it is leaving CB21 and not making it to K1-86, you are loosing it along the path or thru the VIM. If the VIM neutral relay is cycling with the main switch, it could have a bad contact in the neutral relay…

Did you get voltage over at the frequency box?

Are you testing with the same meter in the same way? When I do this I connect the black lead of a voltmeter to the ground test lug in the power panel, then confirm it is working by measuring that it will reliably measure the 12 and 24v at those test lugs in the panel when I apply the red lead There. Your troubleshooting is only as good as the reliable intel you collect…

 

[ghog50cal]

i have power getting through cb21 i have not gotten power over at the frequency box yet I’ve checked my meters against each other and there working correctly on a constant

 

[ghog50cal]

I don’t know what I did but I now have power at k1-86 still no start from the switch

 

[ghog50cal]

Now

I don’t know what I did but I now have power at k1-86 still no start from the switch

when I press the start button I’m getting a click in k1 now but the starter is not activating

 

[Ronmar]

Did you mean K1? If so thats good means all is currently working in the cab. K1 feeds 24V down to the aux start relay on the frame right behind the power steering reservoir. I would pull K1 and make sure it has 24V on i believe socket 30 to send down to the aux relay when it energizes.

if it is there, look to see if it is reaching that frame aux relay and that its coil has a good ground connection…

 

[coachgeo]

charge your batteries individually.


clean all contacts at the LBPD? think that is the right name.. the thingy at spare tire. AKA wondering if a bad connection at at LBPD or battery (or a bad batt) shows it all measures fine voltage with a meter ... but then fails when you really load it...

AKA... its always something simple stupid lol

 

[ghog50cal]

yes I meant k1 sorry

so pin 30 is constant at 23v
Pin 86 has 23v constant
Pin 85 has 23v constant

and when I press the start button pin 87 gets 23v

 

[ghog50cal]

I have load tested the batteries and there on the charger now so I don’t drain them as I’m working on it I looked at the lpbd again last night and it looks clean with no issues checked too see everything was tight back there also

 

[Ronmar]

Thats with the relay in place? Sounds right, the relay coil is a wire so the voltage on 86 will be felt on 85 ntill the button is pressed. The voltage on 87 when energized is what is sent down to the aux relay, so you need to look for that voltage down there.

You should also be able to pull K1 and measure resistance from socket 87 to ground. there should be a circuit from socket 87 down thru the aux relay coil to ground…

 

[ghog50cal]

yes that’s with the relay In place

87 too ground is OL

 

[Ronmar]

yes that’s with the relay In place

87 too ground is OL

So could be a bad aux relay on the frame or a disconnect down there. I would look for voltage from K1 making it down there.