A3 electrical problems continue on

[househaunter]

We've had our A3 for three years now and I finally got the light switch diagnosed and replaced, fixed the air problem to the winch and the brake light switch. I still can't get turn signals and find nothing wrong anywhere except maybe the turn signal lever. With that said, its been great. However, I took it out the other day and I noticed the CITS didn't power up either did the tachometer or brake lights. I checked the two circuit breakers I know of and they were fine. Is there a circuit breaker I'm missing or something I'm overlooking? It seems like its a power problem to several systems that should run through a circuit breaker system, but I can't find a common thread why all these systems would just die while sitting a few weeks. Any thoughts?

 

[cattlerepairman]

Bad ground would be on the top of my list.

 

[JohnnyBM931A2]

Sorry to hear man.. That sucks

 

[househaunter]

I checked the grounding to the unit and as many placed and systems I could check. Grounds seem solid. I found that this truck was missing the flasher unit so I got that replaced and working. I checked the voltage at the CTIS head. No voltage there. So, something happened to cause the tachometer and CTIS power to fail. Checked circuit breakers... they're fine and should reset anyway. Is there a fusible link or some reason that power would fail to the CTIS and tachometer? They dropped out at the same time when the truck sat or when it was started. They've always worked, but no voltage there now. This A3 has had no issues really and only has 2900 miles on it. I've tried to track down a schematic to see where that voltages comes from and haven't been able to find something detailed enough. Is there a terminal block on the firewall?

 

[steelandcanvas]

Does this help?

TM 9-2320-386-24-1-1, section VIII.

 

[househaunter]

Happy 4th of July everyone. Well, 5th. I have been digging in to the wiring on the M35A3 trying to get the CTIS working again. The CTIS controller is dead. I am lost. I've referenced the service manual as much as possible. There are two connections plus a ground on the CTIS. I have voltage at the smaller connector which seems to be for illumination. No voltage at the larger plug. I can't find where this voltage comes from. I don't know that I've found all the circuit breakers, but I don't know that I haven't. I find conflicting information from people, webpages and data. The A3 sits sadly with flat tires. Not that I can't go blow them up, but its not convenient.

Finally, I broke down and replaced the CTIS controller with an NOS one based on a few people being certain the controller was dead. Nope, that was not the problem. Same issue, CTIS is dead.

Anyone have any solid leads or information as to where this power comes from in the truck, which circuit breakers or anything? I'm half tempted to just jumper it to the 24V line and bypass what I can't find. Hate to, but this is going on a year now and as the truck sits, snow collapsed the soft top which let more water into the cab in the winter. I've got to fix this thing this summer.

Any help would be greatly appreciated.

 

[cattlerepairman]

The A3 sits sadly with flat tires. Not that I can't go blow them up, but its not convenient.

Not to add to your woes, but the CTIS has been unreliable, even when the trucks were still on active duty. The original tires are prone to internal breakage from sitting without air often and/or for prolonged periods of time. That makes the original A3 tires a risky proposition with regards to blowouts at speed. This has happened to several members here and there are threads about it. Something to be aware of.
CTIS on the A3 has several design challenges and some of the parts are hard to come by. It can be disabled and also completely removed. If done right, many concede that it makes the A3 a more reliable truck.

There is a current discussion about this: http://www.steelsoldiers.com/showthread.php?155978-Value-of-CTIS-on-M35A3