Electrical nightmares

[New2School]

Ok so here my electrical nightmare so far…

Bought the bus, guy said he put new batteries in it… starts fine till the day I go buy it. Get it jumped, limp it home on six bad tires. Let it run to hopefully charge up.

Try to start it the next day, won’t run… both batteries are dead…install $350 in new batteries, still won’t start..trace the problem to the back door safety relay…bypass it and cranks and runs like a champ.

Two weeks later (today), I crank it to move it and let it run for a bit…a little hesitation, but whatever… park it, try to start it back up…won’t even turn over. Gauge is reading 10v on the crank attempt and the fuel gauge seems to have stopped working (showing full). Check the batteries…when the master switch is on, one reads 11.5 and the other 12.3…when switch is off I’m getting 12.3 on both.

1993 international 3700 with a Thomas body… any wiring diagrams or ideas?

 

[A_Bus_Called_Quest]

Not a pro - but could part of the safety relay be always-on and draining the battery? I feel like that is the only system that could be active even when the ACC power is turned off. . . that or lights or something but you would see those on.

 

[bus-bro]

If you don't have a battery disconnect switch, install one. When parked for more than a few hours open the disconnect.

 

[BamaBus]

Two weeks later (today), I crank it to move it and let it run for a bit…a little hesitation, but whatever… park it, try to start it back up…won’t even turn over.


Automatic? Which Engine? A/C? Lift? Do you have the 40 amp inline fuse in the battery compartment. Maybe jumper past master switch to verify it's not an issue but I guess you are getting light at dash and all that action. If auto not being in N at the trans itself could be an issue. Verify shift linkage is doing it's job.

Gauge is reading 10v on the crank attempt and the fuel gauge seems to have stopped working (showing full).
Its an International. Gauges work when they want.
Check the batteries…when the master switch is on, one reads 11.5 and the other 12.3…when switch is off I’m getting 12.3 on both.
Disconnect then check.
… any wiring diagrams Good luck with that

..........

 

[New2School]

Two weeks later (today), I crank it to move it and let it run for a bit…a little hesitation, but whatever… park it, try to start it back up…won’t even turn over.


Automatic? Which Engine? A/C? Lift? Do you have the 40 amp inline fuse in the battery compartment. Maybe jumper past master switch to verify it's not an issue but I guess you are getting light at dash and all that action. If auto not being in N at the trans itself could be an issue. Verify shift linkage is doing it's job.

1. Allison 545at
2. 7.3 idi na
3. Has ac and lift
4. Has the breaker between the batteries

 

[BamaBus]

Two weeks later (today), I crank it to move it and let it run for a bit…a little hesitation, but whatever… park it, try to start it back up…won’t even turn over.


Automatic? Which Engine? A/C? Lift? Do you have the 40 amp inline fuse in the battery compartment. Maybe jumper past master switch to verify it's not an issue but I guess you are getting light at dash and all that action. If auto not being in N at the trans itself could be an issue. Verify shift linkage is doing it's job.

1. Allison 545at
2. 7.3 idi na
3. Has ac and lift
4. Has the breaker between the batteries

You shouldn't have the 40 amp fuse for an ecm with the idi but you should have the (100amp?) breaker for the lift. When you said "a little hesitation" was that like a weak battery and a slow crank? Any noises or anything when turning the key on restart attempt? Maybe bad alternator. My 98 Thomas would kill batteries and I think it was the ac. There was a little light on a circuit board that I could not to get to go out after pulling every fuse I had. Finally just pulled the battery cables off. i also disconnected the power cable to the lift in the batt compartment.

 

[Nawbdy]

I agree with those that say to disconnect the batteries when not expecting to run it for a while. Just today I ordered a cutoff switch so I can disconnect without having to pull a terminal.

You could try performing a parasitic loss test. You can search YouTube if you don't know how. If your bus is like mine there are splices and jumpers all over the place, who knows what some hamfisted mechanic might have done.

 

[A_Bus_Called_Quest]

I agree with those that say to disconnect the batteries when not expecting to run it for a while. Just today I ordered a cutoff switch so I can disconnect without having to pull a terminal.

You could try performing a parasitic loss test. You can search YouTube if you don't know how. If your bus is like mine there are splices and jumpers all over the place, who knows what some hamfisted mechanic might have done.

What switch did you go with / is any switch rated for 12v OK? I've seen a few Auto / RV / Marine 12v switches on the 'Zon and am going to order one in the next week or so.

 

[Nawbdy]

What switch did you go with / is any switch rated for 12v OK? I've seen a few Auto / RV / Marine 12v switches on the 'Zon and am going to order one in the next week or so.

I'm not that knowledgeable but someone recommended a Fastronix. I ended up getting a 2 post switch with a 180 amp continuous rating, 1000 amps intermittent. Apparently those are popular in racing applications.

https://www.amazon.com/Fastronix-Current-Master-Battery-Disconnect/dp/B011EYWMDS/ref=mp_s_a_1_3?crid=2IOMIE255O2W6&keywords=fastronix+2+post+disconnect&qid=1654903049&sprefix=fastronix+2+post+disconnect%2Caps%2C165&sr=8-3