My '84 Allegro has a 6.5 NH generator with an hour meter in the dash. The generator runs, but the hour meter doesn't. I guess the question is: how does the hour meter work? There are 2 wires on the back of it. Both house batteries are new and charged, but the battery health monitor (also part of the Onan panel) does not have a reading. Could this be part of the problem?The generator has either been replaced, or at least removed and re-installed. The connector at the generator is spliced in. I checked the continuity of the splices (all good) and checked the wiring to the panel versus the Onan manual (all good, too).It's a minor problem compared to the fact that I don't have a running 454 in the rig right now, but I'd like to fix it.

The hour meter works by a 12 volt positive signal that the genset sends to the remote start switch next to the hour meter. IF the remote switch light is NOT on then the 12 volt signal is not there. The genset starts from a ground system and does not use 12 volt positive connections to start and stop. The battery indicator on your dash remote is a separate 12 volt signal to the remote. The hour meter just has a ground (negative) wire and the 12 volt positive that the genset sends out. It is common for such an old hour meter to not function. Doug

Thanks Doug. I'll check for 12V at the hour meter. If I have 12V, then I can assume the meter is bad.

turbojimmy wrote:Thanks Doug. I'll check for 12V at the hour meter. If I have 12V, then I can assume the meter is bad.Yes. Doug

The two wires are 12V+ and ground. Odds are fairly good it is a bad ground but the 12 volt comes from the generators' control computer/ignition system. and the problem could be any wire or connection from there to the meter.. or the meter itself.

Most generators have hour meters on the generators themselves. I have hour meters on the gen, instrument panel and the electrical panel. Don't know how they are wired, but all three have different numbers. I use the one on the generator.

Onan Hour Meter | Good Sam Community

dougrainer
Nomad
Mar 09, 2014
The hour meter works by a 12 volt positive signal that the genset sends to the remote start switch next to the hour meter. IF the remote switch light is NOT on then the 12 volt signal is not there. The genset starts from a ground system and does not use 12 volt positive connections to start and stop. The battery indicator on your dash remote is a separate 12 volt signal to the remote. The hour meter just has a ground (negative) wire and the 12 volt positive that the genset sends out. It is common for such an old hour meter to not function. Doug
turbojimmy
Explorer
Mar 10, 2014
Thanks Doug. I'll check for 12V at the hour meter. If I have 12V, then I can assume the meter is bad.
dougrainer
Nomad
Mar 10, 2014
turbojimmy wrote:
Thanks Doug. I'll check for 12V at the hour meter. If I have 12V, then I can assume the meter is bad.

Yes. Doug
wa8yxm
Explorer III
Mar 10, 2014
The two wires are 12V+ and ground. Odds are fairly good it is a bad ground but the 12 volt comes from the generators' control computer/ignition system. and the problem could be any wire or connection from there to the meter.. or the meter itself.
Blaster_Man
Explorer
Mar 10, 2014
Most generators have hour meters on the generators themselves. I have hour meters on the gen, instrument panel and the electrical panel. Don't know how they are wired, but all three have different numbers. I use the one on the generator.
mlts22
Explorer
Mar 10, 2014
I think the one on the generator goes by spark plug firings, which is likely the most accurate (spark plug * RPM, and on an Onan, the RPMs are constant.)
dougrainer
Nomad
Mar 10, 2014
mlts22 wrote:
I think the one on the generator goes by spark plug firings, which is likely the most accurate (spark plug * RPM, and on an Onan, the RPMs are constant.)

No, They are just 12 volt hour meters. There is a 12 volt positive signal when the APU is running and that is connected to the hour meter. Doug
turbojimmy
Explorer
Mar 10, 2014
mlts22 wrote:
I think the one on the generator goes by spark plug firings, which is likely the most accurate (spark plug * RPM, and on an Onan, the RPMs are constant.)

I don't have one on the generator itself - just on the dash.

And it's interesting you mentioned spark plugs. It was running pretty rough, but I figured it would clean it self out. It shook the whole RV. Turns out it was running on only one cylinder. After some diagnosis I narrowed it down to a bad plug. Put 2 new plugs in it. Wow what a difference. Smooth and quiet now.

Back to the topic at hand....if I put a multimeter across the terminals on the back of the hour meter, I get 12V. Has to be the meter itself. They're cheap enough that I think I'll snag one. I was kind of excited that my 30-year-old generator only had 155 hours on it. But, I wonder when the meter quit?
Passin_Thru
Explorer
Mar 17, 2014
My 7.5 qd doesn't have sparkplugs so rule the spark plug firing out. It does not run at a constant speed, it runs at an optimum RPM for it's load, fully loaded, full throttle. It just counts hours when hooked to 12 V and when a 12 V switch to it is left on it will count hrs whilst not running.
turbojimmy
Explorer
Apr 26, 2014
Here's an update. I installed an eBay hour meter. Direct fit, same wiring arrangement. Still didn't work.

Over the last couple of weeks I put the new engine in and hooked up the chassis battery. Now the hour meter works! Coincidence? Dunno. I could unhook the chassis battery to check but it's not worth the hassle. The old hour meter may not have been broken after all - it may have needed juice from the chassis battery.