Headed down I-84 and noticed that the engine Ecu threw a code. Eng sid 251 52 power supply. So Stopped by a Cummins shop on the east side of Boise.
Techs said that is a generic code that means a low voltage from the OEM side. I.E. bad battery or alternator.
I told them that the chassis batteries sit right behind the drive tires and get really nasty and that I would clean the terminals and charge the batteries after finding a place to park over night. The shop said, hey we have two RV spots with 50 amp you are welcome to park here and charge up over night and see what happens when you start up in the morning.
Super nice folks. And a spotless shop.
Cummins sales and service
8949 S Federal Way
Boise, ID 83716
Be aware that unless modified, shore power does NOT charge the chassis battery unless the boost switch is on AND boost solenoid is working.
VERY easy to verify on your coach.
Do nothing for a couple of hours visa via the chassis batteries.
After they have rested long enough to loose their surface charge check voltage at the chassis batteries. Yes, this wait and then test can be sped up by turning on the headlights or other load that works off the chassis batteries.
If still over 13.0 VDC, you do have some (non OE) method of charging the chassis batteries from shore power (there are several very good aftermarket solutions).
If under 13.0 VDC, turn on boost switch and immediately check voltage at the chassis battery. It should now be exactly the same as voltage at the house batteries.
If questions, let us know-- will leave a light on for you.
Brett. I have a standard agm 2, 10, 20 amp charger as well as a 2 amp trickle maintainer. My coach does not have the chassis charger on our charger/inverter.
And like the dumas I am. I neglected to pack the multimeter.
So I cleaned the posts & terminals. Put the standard charger on. Will put the trickle on this evening.
I had this same code last year. After cleaning connections. The code went away.
At least I'm in the right spot and not in the middle of Timbuktu. We are only 4 hrs From home.
So It's all good.
What was chassis battery voltage when at the Cummins dealer/now? Your dash gauge (not Audit gauge) shows chassis battery voltage. BUT, checking them with a digital voltmeter is a lot more accurate.
LOTS of causes for engine to see low voltage, starting with poor connections at batteries, poor connection at positive or (actually more likely) at the ground connections.
Brett. On the VMSPc. It shows 12.5V. My dash gauge(s) have always been wonky.
Not sure what "wonky" means. Normally dash gauge reads a little lower than actual battery voltage because of voltage drop over the wiring from battery to dash.
But, 12.5 does at the dash sure does not suggest a battery/alternator issue. Absolutely check connections to engine ECU, both positive and ground.
By wonky. When I turn the headlights on. The oil pressure goes down, fuel goes up, voltage down.
There has to be ground fault in the dash some where.
While it's still light out. I may have to grab my can of deoxit. Hopefully that ecu isn't to well hidden.
Yes, the "dash symptoms" suggest a bad ground at the dash.
Boy are those ecu connectors well hidden at the back and behind other cables. Yikes 😬 looks a pita to get at them.
Talked to the shop we are parked at. They said that they can get us in on Thursday. But also said that chasing a bad connection can get to be a lengthy process.
So the plan is to trickle charge the chassis batteries over night and make sure the preheat is on and see if the fault reappears in the morning. If it doesn't. Then off to Walla Walla and have my regular shop work on this.
Update, After giving the start battery terminals a real good cleaning and charging up with a standard charger at 10 amps. Then over night with a 3 amp trickle charger/maintainer. Start Battery voltage (on the vmspc) was 11.9 V.
The coach has been running for a while with no return of that fault code. So off to Walla Walla where we will have our 5 year old red tops checked out. And check out the ECU connectors.
Under what conditions were the chassis batteries reading 11.9 VDC. And what was voltage at the battery when it read 11.9 on vmspc?
What is reading with the engine running, say at 1,100 RPM?
When you turn on your headlights and things go wonky it also could be a poor positive wire or connection.
I killed a couple of sets of redtops until I did what the new coaches have done.
I added a blueseas auto battery combiner.
The charging on AGM red-top starting batteries like almost all other batteries needs to be 100% reliable.
Each time they are over discharged the capacity can be reduced.
I came around to the auto battery combiner like the rest of the industry has to prevent inadvertent damage.
Only takes once.
As far as I know ALL new coaches come with combiners. Am I wrong?
Nearly impossible to be 100% correct on separately charging engine start batteries.
I had several small chargers fail and let the start batteries run down.
Small solar and the combiner fixed this. We are la shaky town residents.
The coach needs/has to have fully charged batteries every time
Actually, if the dash gauges go wonky, it is more often the dash ground.
Brett, The 11.9 was a few minutes after removing the trickle charger and prior to starting the engine with the key on and VMSPc on. Right after starting, the VMSPc readout went to 13.6/13.8V. All the readings were from the VMSPc screen as I accidentally left my multimeter at home.
Drove the short distance to Ontario where we are waiting for a wash job. So far no code.
Stop and have the batteries load tested AFTER driving far enough to bring them to full charge.
Yep, as we are so close to Walla Walla (home) 4 hours. we will do that there.
Thanks once again for your guidance Brett.
Update: Made it back to Walla Walla without another code. Will get the start batteries load tested shortly.
Put a nice long charge on the start batteries with both cables off but interconnects on. reconnected and went to the shop.
all three batteries test good. In fact the guy testing asked how old they were. When I said 5 years old. He said they tested like they were much newer. I think the worst reading was 30 amps down from the rated 870 CCA. one was right at the CCA rating. the other was down 10. They were all right around 13.4 Volts.
Next step will be to have the shop check the ECU connections when I have them change the hydraulic fluid/filters.