M1088, Previous Runner, now no power at all... ideas?

yes, i have the manuals, yes im going through the flow charts etc... but nothing like experience...

The truck was driving fine, we drove it home from the Auction... it had air brake issues, and i had to replace a rear inversion valve, air dryer and the Governor/unloader on the air compressor... manual cab tilt pump reservoir was low, needed to fill to tilt the cab.. it hasn't been running in over a month waiting for parts...

after all that it wouldn't even power up...

- the batteries are known good.
- the battery hookup is correct and the same as before when it ran, and i double checked
- i serviced the battery connections, and they are all clean and tight
- i checked voltage inside the passenger side circuit breaker box 12 and 24v and there is voltage there
- all the breakers "seem" ok (not popped)
- master power switch on dash does nothing, no lights no power, and no draw an an ammeter

anyone have any ideas on this one?

Chris

How do you know the batteries are good? I would recommend charging the batteries. If you don't have a 24 VDC charger, use a 12 VDC charger and charge each battery separately. I had a 6TL battery in one of my deuces fail unexpectedly. Headlights worked. Starter wouldn't turn over. I discovered the bad battery by using jumper cables to my car separately for each battery in the deuce. Jumping the second battery with the cables, the deuce started right up.

glcaines said:

How do you know the batteries are good? I would recommend charging the batteries. If you don't have a 24 VDC charger, use a 12 VDC charger and charge each battery separately. I had a 6TL battery in one of my deuces fail unexpectedly. Headlights worked. Starter wouldn't turn over. I discovered the bad battery by using jumper cables to my car separately for each battery in the deuce. Jumping the second battery with the cables, the deuce started right up.

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Each battery was disconnected and removed for service. I used a digital and analog battery load tester and they all passed. fine...additionally i have a large Schumacher boost box in 24 v ( i use it to start multiple large MCI tour busses without issues) and tried with that and it had no affect.

I could imagine that if the batteries were "low" i would get at least dash lights... i get absolutely nothing in the dash...

unless there is a hidden shut off switch somewhere, i guess going through each breaker and testing them is next...

Chris

Voltage check at power panel test points = good. Not testing While under load = bad... gotta test when loaded(switch turned on) or they don’t count.

what year truck?

when you turn on the Main switch, it energizes the instrunment power relay K2 In the PDP. I would start there. 12v flows from the test point in the PDP, thru CB70 To the Main switch, back to K2’s coil(pin86) and pin 85 connects to Terminal board 2(tb2 = ground) to complete the circuit that powers rely K2...

Oh, and the breakers seem a little fragile to me. I kept a few for testing/troubleshooting, but replaced them all with standard automotive blade fuses. Way more predictable, especially when you add in vibration...

Ronmar said:

Oh, and the breakers seem a little fragile to me. I kept a few for testing/troubleshooting, but replaced them all with standard automotive blade fuses. Way more predictable, especially when you add in vibration...

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That is an interesting idea what is the max voltage rating for the ones you installed. It would be easier to see a blown fuse than Trying to figure out if the CB is bad

for some reason my phone had me.logged in on this account... was an old one.. sorry for any confusion...

Ronmar said:

Voltage check at power panel test points = good. Not testing While under load = bad... gotta test when loaded(switch turned on) or they don’t count.

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yea i did test voltages while attempting to turn on and off truck lights etc.. absolutley nothing.. and the voltage stayed the same, never moved.. makes me think there isnt any load at all.

what year truck?

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1997

when you turn on the Main switch, it energizes the instrunment power relay K2 In the PDP. I would start there. 12v flows from the test point in the PDP, thru CB70 To the Main switch, back to K2’s coil(pin86) and pin 85 connects to Terminal board 2(tb2 = ground) to complete the circuit that powers rely K2...

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perfect! ill start with that in the AM

thanks...

codematic said:

for some reason my phone had me.logged in on this account... was an old one.. sorry for any confusion...




yea i did test voltages while attempting to turn on and off truck lights etc.. absolutley nothing.. and the voltage stayed the same, never moved.. makes me think there isnt any load at all.



1997



perfect! ill start with that in the AM

thanks...

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Well if you cannot turn on the lights, start with CB70. In addition to feeding power to the main switch to power the K2 relay, it also feeds power to the lightswitch....

standard 12v automotive fuses will be fine For both the 12 and 24v circuits...

Ronmar said:

Well if you cannot turn on the lights, start with CB70. In addition to feeding power to the main switch to power the K2 relay, it also feeds power to the lightswitch....

standard 12v automotive fuses will be fine For both the 12 and 24v circuits...

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you called it, k2 was bad.. replaced it and it started..

thanks..

chris

Cool!

Ronmar said:

Cool!

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im not a fan of these breakers i must say.. i think im gonna go old school...

thanks again...now on to the next problem.. i several military vehicles and it seems you really never get them all "fixed", you just move oo to the next issue..

chris

The fuses work fine, I keep a few of the breakers as they are handy when troubleshooting intermittent short circuits...

Ronmar said:

The fuses work fine, I keep a few of the breakers as they are handy when troubleshooting intermittent short circuits...View attachment 808549

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do I recall right that when using 12v fuse n 24v location you have to double the amp value? (or is it the other way around? )

coachgeo said:

do I recall right that when using 12v fuse n 24v location you have to double the amp value? (or is it the other way around? )

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Because they are melting the fuseable link, the difference is not very significant. Many of the fuse packages actually say 12 or 24v...