having an issue understanding the TM

[gstirling]

having a fuel gage issue (M936) and am reading TM 9-2320-272-23-1 pp 0107-5, checking the wires and fuel switch - step f states to connect circuit 28 to red lead, and step g. black to ground, then step h states meter reading should be 5 to 8 vdc... totally clear. what confuses me is the NOTE - if 5 to 8 vdc is present selector switch is faulty. so step h just tried to get 5-8 vdc?
I would have thought step h (5-8 vdc) was good? note says opposite??? what am I misunderstanding?

 

[99nouns]

Having issue understanding a TM is a common issue...

Sometimes you have to understand it backwards, I am sure you are not reading the TM just because of you are bored or doing a quality inspection, so it will tell you what the fault should be rather than telling you what it should be, because that TM knows exactly what the fault will be.

 

[rchalmers3]

I say go with your instinct. Most gauges are supplied with voltage limited power. I think you may have found a typo in the manual.

Rick

 

[simp5782]

On the fuel sender and junk. You need to ground your gauge first off. I would ground all the electrical gauges to a known good ground. They ground thru the dashboard covered in carc. Not always great. Especially in your bumpy log road conditions. So ground all wires and eylits to all the hold downs and run it to a good ground somewhere in the cab. or even in the engine bay.

Then clean your ground on your fuel tank and at the frame. or run a new one as I would do. Then worry about voltages. Fuel gauges in these trucks generally suck. Especially on a dual tank system cause of the little selector for the tank can also have an issue. on every fuel gauge problem I run into simple for me to replace the gauge, ground it. run a new wire to the tank and install a new sender. Cost around $100 for everything and its known good, but i still don't trust em.

 

[gstirling]

yeah i had earlier cleaned all the dash grounds last time i opened the gauge panel up, replaced both the intank sensors when i first got the truck (2 yrs ago). I think i will add in a few extra ground wires while its open as you suggested. was trying per TM to figure out if the switch was going bad or the gauge...and the TM confused me. the troubleshooting did not...LOL. also what started this was a blue flash the other day when driving as i switched tanks on the gauge, found a burn mark on one of the fuel gauge posts when i pulled it out.