CTIS 24v conversion

[Russ Hersh]

I was doing some reading and saw that the CTIS on fmtv's, m916's were 24v, so if someone did a conversion from 24v to 12v. would the system still function or would you have to change the CTIS to 12v? if so how can it be done?

 

[Andyrv6av8r]

Why convert in the first place?

 

[Russ Hersh]

So turns out that stepping down isn't as large of an issue depending on the system you're powering. Reason for the conversion from 24v to 12v is fleet wide standard everything runs on 12v and a lot of the 24v systems weren't going to be used. Either way it appears that theres no power running through the fuse slot for the CTIS system.

 

[Ronmar]

Well the CTIS needs 24V(i am not aware of a 12v version) so you would have to provide it 24v somehow to keep this CTIS system... I don't understand the “no power running through the fuse slot for the CTIS system” statement. CB40 provides 24V to a pin on the CTIS connector...

 

[Russ Hersh]

Well the CTIS needs 24V(i am not aware of a 12v version) so you would have to provide it 24v somehow to keep this CTIS system... I don't understand the “no power running through the fuse slot for the CTIS system” statement. CB40 provides 24V to a pin on the CTIS connector...

so on the fuse panel under the dash in the cab (on m916a3) slot labeled "CTIS 24V" was tested for voltage and no voltage was present. checked for short and no continuity was found. so to get the 24V out of the 12V conversion i have to run a power wire from 2 batteries? (if i have to go that route. prefer not to).

 

[Ronmar]

Not familiar with the 916 but I would say you have a wiring issue. You could get 24V from 2 batts, but how would you charge the batteries?

What you need is a 12-24V power converter capable of meeting the peak current demand of the CTIS...

 

[Russ Hersh]

Im thinking something did get disconnected when it went in for 12v conversion, truck has trickle charger hooked on to maintain batteries when truck is shut off and disconnect on the off position. I have considered the converter but looking at the wiring it doesn't appear that it draws that much current given that the wiring leaving the fuse panel for the ctis is about a 12ga if that.

 

[Ronmar]

Well if it was converted to 12V then everything 24V was probably disconnected. The CTIS controller is a microprocessor and probably needs its designed voltage to function. A given amount of work performed at 24V takes half the current of the same work performed at 12V so 24V uses a smaller gauge wire. At any rate I believe the solenoid valves on the PCU probably have 24V coils and may not perform as well(and certainly pull more current) if you try to run them on 12...

 

[Russ Hersh]

Fair enough point on current draw, so a 12v - 24v boost/step up will probably on its way here shortly. its still interesting that im not reading any voltage from the CTIS fuse slot. In any regard thank you for the assistance it probably has saved me from damaging components that are already expensive.

 

[SausageGuy]

This whole thread does not make sense as you would still need 24v for starter so might as well leave alone. Right?

 

[Russ Hersh]

This whole thread does not make sense as you would still need 24v for starter so might as well leave alone. Right?

24v starter was replaced with a 12v starter in the conversion process of the truck