Community Forums

voncluck · 10-12-2015, 09:29 AM

We are preparing for a trip in our RV but I need to fix a couple of things first. The air gauges flop from 0 - 130 as if there is a short. In the heat of the summer the heat gauge rose when engine was pulling up an incline. I feel there is either a short or bad relay. Other than visual checking the wires I do not know how to solve these issues.

2 Stroker · 10-12-2015, 09:44 AM

Quote:

Originally Posted by voncluck

We are preparing for a trip in our RV but I need to fix a couple of things first. The air gauges flop from 0 - 130 as if there is a short. In the heat of the summer the heat gauge rose when engine was pulling up an incline. I feel there is either a short or bad relay. Other than visual checking the wires I do not know how to solve these issues.

Your air gauges have no relays, they are not electrical. It has a line right to your air tanks. Problem with the gauge or your compressor or a leak in the lines. If you get below 60 + or - psi your brakes will apply on there own.

What make of coach do you have.
2 stroker

FIRE UP · 10-12-2015, 10:53 AM

Quote:

Originally Posted by voncluck

We are preparing for a trip in our RV but I need to fix a couple of things first. The air gauges flop from 0 - 130 as if there is a short. In the heat of the summer the heat gauge rose when engine was pulling up an incline. I feel there is either a short or bad relay. Other than visual checking the wires I do not know how to solve these issues.

voncluck,
Well Sir, it would be nice to know your make/model/engine/chassis/etc. of the coach involved. You see, in the older, as in around '03 and older Freightliner chassis equipped coaches, they used what's called the VDC or, Vehicle Data Computer for transmitting all engine ECM, Transmission TCM, ABS Module and, Air pressure system information to the gauges. That VDC in those chassis's was primarily located on or near the frame, very close to the engine.

As stated, there's inputs from the primary and secondary air systems that enter that VDC. There are what's called "Transducers" in that VDC that have solder joints on them for changing mechanical input to electronic output. And, those solder joints have been noted, several times on here and other RV forums, to turn into what's called "cold solder joints". And those are simply BAD solder joints.

The remedy for many guys here has been to remove that VDC, set it on the workbench and, get it torn down to visually check those joints. Then, break out the solder gun and, re-heat them to re-connect them. Many have had good success at it. Others have just had to purchase a new VDC. So, hope this helps some.
Scott

deandec · 10-12-2015, 11:34 AM

Coolant temp normally will rise when straining uphill in high summertime temps.

How high did it rise?

voncluck · 10-13-2015, 11:06 AM

Thanks for the replies guys. Sorry, I failed to mention I have a 2000 Sportscoach, 275 cummins diesel with about 42000 miles on it.

gfs1943 · 10-13-2015, 05:48 PM

Quote:

Originally Posted by FIRE UP

voncluck,
Well Sir, it would be nice to know your make/model/engine/chassis/etc. of the coach involved. You see, in the older, as in around '03 and older Freightliner chassis equipped coaches, they used what's called the VDC or, Vehicle Data Computer for transmitting all engine ECM, Transmission TCM, ABS Module and, Air pressure system information to the gauges. That VDC in those chassis's was primarily located on or near the frame, very close to the engine.

As stated, there's inputs from the primary and secondary air systems that enter that VDC. There are what's called "Transducers" in that VDC that have solder joints on them for changing mechanical input to electronic output. And, those solder joints have been noted, several times on here and other RV forums, to turn into what's called "cold solder joints". And those are simply BAD solder joints.

The remedy for many guys here has been to remove that VDC, set it on the workbench and, get it torn down to visually check those joints. Then, break out the solder gun and, re-heat them to re-connect them. Many have had good success at it. Others have just had to purchase a new VDC. So, hope this helps some.
Scott

This worked for me, just as Scott said. Once I got the VDC out and the cover off, the solder joints didn't look that bad, but I resoldered all of them on the air transducers (four wires on each transducer, if I remember correctly). I also reworked a few others that looked a bit corroded.

My original problem was only with the front air gauge; sometimes it would drop to zero and the warning buzzer would come on, other times it would bounce between 30 and full-scale on the gauge. Any time the indication dropped below about 60 psi, the buzzer came on.

Whether it was the solder joints or just dirty wire connections, I haven't had any problem with the indicators since I did this repair. It's not that hard to do.

deandec · 10-13-2015, 06:22 PM

Quote:

Hafe way between normal and hot, but service engine would come on at same time.

My 300HP Cummins C8.3L engine will shut down at 225 degrees after a warning alarm.

185 degrees is normal for the thermostats installed in my Cummins.

Half way would be about 205 degrees which is where the thermostat is just reaching full open stage and is yet another normal.

Your heat situation does not seem onerous but the Service Engine Light does!

Check your coolant and oil levels. Are they ok?

What factors lead you to focus on an electrical/gauge malfunction?