Electrical system question

[David49]

When I start the engine on my coach, I typically watch the gauges to make sure everything works like it's supposed to. Recently I noticed that after a cold start, the ammeter initially shows charge, then after a few seconds, there's a click and the ammeter goes slightly negative. After a few seconds, another click and the ammeter shows positive. This cycle repeats about three or four times and then the ammeter stays on the positive side.

I haven't noticed this happening after a warm start although I can't swear that it doesn't.

Any idea what's going on here and is this normal for this chassis?

[Monacoach]

When starting our coach the needle stays low for a minute or two and then moves to pos side permanently. Sounds like its doing the same thing as yours more or less. I think it may have something to do with the isolator relay solenoid where as the chassis battery charges first then the relay clicks closing a circuit to connect all batteries so that the house batteries can charge. Takes longer when the chassis battery is low ( I just found this out and it makes sense) such as when its cold out. Not sure why yours goes back and forth but if it levels out I think its probably doing what it should.

[Pusherman]

Could be the engine air intake heater continues to cycle until the sensor says 'warm'. My '00 Cummins did this.

[wa8yxm]

One posibility. Another is the house batteries, if they are low, may be taking the system down and the ammeter is only monitoring the chassis battery.

After a few short cycles of charging they are up enough for the breaker to hold.

I have seen that pattern in my gasser a few times, though I don't have an ammeter. But i've heard the isolator (Which is voltage senistive) cut in an out a few times and noticed the effect on house v/s chassis devices.

[MaverickBBD]

I would cast my vote for the engine air intake heater. Does it do this if you give the engine some pre-heat time?

[David49]

Thanks for all the replies. I do wait for the preheat cycle to complete before starting. House batteries were replaced last year, and chassis batteries last month.

[Pusherman]

Quote:

Originally Posted by Pusherman Could be the engine air intake heater continues to cycle until the sensor says 'warm'. My '00 Cummins did this.

It may continue to cycle even after you complete the 'wait to start' cycle. Thus why you see your voltage gauge fluctuating after starting for a few more seconds.

[David49]

Thanks to all! I feel better knowing it isn't something I need to be concerned about.

[JBDISCOVERY]

David,
It is the inlet air heaters that are cycling. I asked the Cummins rep at the FMCA rally at Perry, Ga. this spring. He said that the voltage drop is when the heaters kick on. Not a problem. All is working well.
JB

[Skip426]

Looks like I'm a little late with this reply. But on Dodge trucks; Cummins; on a long downhill coast in cold temps the intake heaters will cycle if the intake manifold temp drops to approx 55f. So don't panic if you get a volt drop then, or in very cold weather after prolonged idle.

[David49]

Thanks JB. Good info.