Intermittent "alt charge" warning

[Dancing Bear]

My 2008 Cayman with Cummins ISB has started giving me an intermittent "alt charge" warning light and bell. Usually towards end of full day of travel. However, yesterday during first 20 minutes of travel then nothing for rest of day.

Voltage gauge never flinches, always over 13 volts. Sometimes bell and warning would start at higher rpm (2500) and go away at cruise (1700). Not always and no consistency.

Lights and batteries never affected. As I indicated, voltage gauge on dash does not flinch during any of this. Always 13+.

Ideas?

Thanks, John

[Kurt.kroll]

Check Belts?

[walt2137]

Check your Hamsar relay sounds like its causing the problem.

[Robi.1014]

On the back of the alternator are connections for "Positive Output" (goes directly to the starting batteries), a "Battery Sense" (ditto) and "Alt Fail Relay". Check for loose connections at the rear of the alternator as well as any connectors in the path of the wires leading away from the alternator.

The fact that your dash meter is rock-steady makes it difficult to guesstimate the actual failure. But the troubleshooting drill includes checking all battery connections (chassis and house) for firm/clean connections. If nothing is found amiss, then proceed to check each battery with a battery load tester (it could be that one battery is going bad...and the alternator doesn't "like" charging a failing battery).

[Dancing Bear]

Belt appears fine.

Walt - what and where is Hamsar relay?

Rob I - checking, cleaning connections. I fear it will be a drawn out chase as I can't get it to do it routinely...

[EngineerMike]

If you can move any of the connections on the alternator, that's probably it. Past that, its hunt & peck.

[bgj6905]

was your generator running at the time of the light?
Mark
2002 HR Ambassador
USAF Retired
Michigan

[walt2137]

John it is generally under the driver side in the fuse compartment and it gets a signal from the alt to turn off the little idiot light when they go bad no signal.
If you cant find it call Monaco or look at your Elec drawing if you have one. If you are not able to get any info from Monaco I will go to my Coach later and get the part #

John the part # 41120 for the Hamsar and you should also have a 5 A fuse you need to check and Mark is correct sometime when the Gen is running the alt light will also come on .

[deSanford]

On my ISB 340 Cummins I had a alt failure light on the dash come on. It turned out to be a relay went bad. I don't remember which relay, but the folks at Coburg Service Center knew which one it would be and sent it to me (of course there was a "charge"). deSanford

[H. Miller]

We had approx. the same situation and found:
1. The voltage gauge reads battery volts so not much help.
2. While checking for loose wires at the alternator we found 2 or 3 smaller (cannot remember exact number) wires coming out of the alt. and going to a black plastic box, about the size of a cigarette pack, a foot or so from the alt. When opened it had 2 five amp fuses - one was blown. Replaced and no trouble now (2 years).
Couldn't find them on a wiring diagram but feel they are "field" fuses so only 1/2 the system was working.

[86 Cavalcade]

The five amp fuses are in the ignition excite wire and the wire that goes from a alt field terminal to the Hamsar relay that operates the alternator light. I installed a 200 amp Delco on my coach and could not hook the ignition excite wire up because the Cummins would keep running even when I shut the key off. I called Delco and one of the engineers told me to disconnect the excite wire because this brushless Delco alternator did not need external excitation to work. I have run this Delco for thousands of miles and have been very happy with it. On my coach all of the wiring insulation is stenciled on the insulation what it is. I have not found anything yet that was not marked. George 2001 Diplomat PBD

[patmsp]

Don't know if I can help you but my Alt Fail light came on permanently. I checked the battery isolator (while the engine was running) and it should good alternator output. I suspected the relay. Mine is located in the last panel, passenger side and it is the last one of about 10 of them that control idiot lights and safety features. Googled the Bosch number on the relay, and replaced it and all worked. I took the previous one apart and it was fried inside.

[deSanford]

Must be the same relay I had to replace a few years ago. My charging system still was charging, but the light was "ON". deSanford

[Dancing Bear]

Thanks everyone. I will begin the search for relays and fuses...