m920 24 volt delete

[terraglide]

Howdy,
I have an m920 that i've put a 12 volt starter on and i want to abandon the 24 volt side of the electrical
system. The 24 volt rectifier on the alternator is out, but the 12 volt side still works. I can't seem to find a
schematic on an m920 and when i disconnect the 24 volt portions of the system that I'm aware of, I get
a breaker clicking in the dash. Anyway, if there's anyone who can help with this, I'd really appreciate it.

Thanks in advance,
Parker

 

[terraglide]

converting my m920 to 12 volt

Hello,
I'm trying to basically abandon the 24 volt side of the system on my rig. I've installed a 12 volt starter
and when I disconnect the 24 volt circuits that I'm aware of, I get a clicking relay in the dash.
I've looked at the m915 A1 diagram, but not sure it's the same as the M920. The truck is used as a water
truck and no 24 volt system is necessary to my knowledge.

Thanks for any help
Parker

 

[Cycletek]

opcorn:opcorn:............Wait for it!..........

 

[Cycletek]

Be prepared for a lot of work since most of the wiring and cabling will be under sized. All the gauges that use voltage signals will have to be changed. Why 12volts?

 

[NDT]

Go to JAtonkam35.com website and view TM9-230-273-20, figure 5-37 et al will explain the wiring. The o.e. giant battery cables will be fine for 12 volt. The 24 volt delete is a really good idea for most users. The transformer rectifier is a ticking time bomb on these trucks, and will burn up (literally) at the worst time.

 

[m16ty]

You're not going to like the starting on 12v. I have to ask, why?

I'm not familiar with the truck in question but I'd say that clicking you hear is a 24v relay trying to operate on 12v.

 

[terraglide]

I found fig. 5-37 for the blackout lighting system and it should be of help. paragraph B on that page refers to a complete electrical schematic as well as the vehicle wiring harness diagrams in appendix D of that manual, but when i go to appendix D, it's not available. Is there any way to get to that information?

 

[terraglide]

The rectifier on the 24 volt side is out, and it costs $500 to replace. most folks i talk to tell me that those rectifiers are a train wreck. I have no need of a 24 volt system and with the 12 volt starter, it starts fine with a 12 v supply. I just don't want to maintain a costly 24 V system that I don't need.

 

[Warthog]

Combined your two threads.

Posting the same question in different forums is termed "cross-posting" and is not allowed.

 

[NDT]

You are right, the master schematic is not in the manual I posted, but the M915A1 schematic in the -20 manual is very very similar, also on the JAtonka site. I checked and it is there, at the very back of volume 3. Seems like all you would need to change is the feed to the in dash starter relay, from 24 to 12 volts. Then just disconnect and insulate the 24V battery lead and alternator lead and tie them off.

 

[terraglide]

The schematic for the M915A1 worked well..once I got it printed out in on large enough paper to see it. You were right, all I had to do was remove the 24V harness from the alternator, pull the 24V lead off of CB8, and hook both 12V batteries in parallel and it worked like a charm. With the 12V starter, it spins like a top. The existing leads to the starter relay in the dash took care of themselves once the batteries were wired in parallel. Thanks for the help.

 

[Triple C]

Hold on there, what happens to the guages, lights etc aren't they 24volt or is only the starter?

 

[NDT]

Hold on there, what happens to the guages, lights etc aren't they 24volt or is only the starter?

The 915 series is sort of like the CUCV. 24 volts for starting, but the instruments and lights are 12V.

 

[Triple C]

915 series, got it. Thanks.

 

[farmer73]

The schematic for the M915A1 worked well..once I got it printed out in on large enough paper to see it. You were right, all I had to do was remove the 24V harness from the alternator, pull the 24V lead off of CB8, and hook both 12V batteries in parallel and it worked like a charm. With the 12V starter, it spins like a top. The existing leads to the starter relay in the dash took care of themselves once the batteries were wired in parallel. Thanks for the help.

Which 12v starter did you go with?