Alternator AMP Rating

[Mike Merchant]

Looking for advice re' the AMP rating on our '09 Contessa 42 alternator.
The short story is that the alternator bearing blew in SW Wyoming, 34 miles from the nearest town. The alternator was a Leece-Neville 185 AMP. The only truck service we could get out to us had a 145 AMP in stock, which we had them install, the alternative being to sit on the side of I-80 for the 4 days of the Memorial Day weekend. Truck service fella said  a 145 was what they installed in "all the semis". Seems to be working fine, voltage stays between 12.6 and 12.9 when under way.
Interestingly, the 2009 Contessa brochure and my build sheet show a 160 AMP alternator rather than a 185.
I any of this any concern or should I really be more concerned about important stuff, like when does Happy Hour start,etc?

[Edward Buker]

It will have to work a little harder using more of its capacity then a 160amp or 185 amp. They have some built in thermal protection in the regulator where it monitors temperature and de-rates itself as far as amp output, if it starts to get too hot. I would not worry too much about it. Just be sure and charge the house batteries using the generator and inverter/charger if your house batteries have been discharged some while off the grid. The 12.6 to 12.9V underway is at the dash with blowers etc on so the battery is seeing more voltage.

I had my Leece Neville rebuilt this last winter and on the back of the alternator is a large heat sink assembly holding some of the electrical components. It had quite a bit of diesel soot and grime in it from 10 years of use. I would check that area with a mirror every few years and if you see build up that would prevent cooling, see about getting it serviced. That is one issue we have with diesel pusher configuration, is grime build up, and limited cooling of the alternators.

Just be a little conscious of load and know that it has its limitations and you will be fine....the biggest loads are batteries that are down. Next time around, you can get back to the 185amp version, if there is a next time.

Later Ed

[Keith Oliver]

So just when does Happy Hour start?

Your alternator has to replace the amperage lost to startup and battery depletion since the last run or shore connection, and keep up to continuing demands while driving.  If those demand exceed its capacity, it will simply run at or near capacity the whole time, so may get warm.  It will have protective circuitry to prevent overheating, but its life may be shorter than one allowed to run cooler.   Coming from the world of older boats, it is rare to see a diesel boat engine equipped with a large enough alternator, so most get to run at or near capacity much of the time, and failures are rare.

If, like most of us, you are connected to shore power or on your genset most of the non-running time, the loads faced by the alternator will be well within the capacity of your 145 amp unit, so the HH question becomes the more urgent of the two.

[Mike Merchant]

Thanks folks for the reassurance. I'll keep an eye on voltage as we travel.
Ed - The voltages I gave were in error. When I check my "main" screen ( in my coach that is direction of travel, odometer reading and voltage ) the voltage is 13.9/14.0 at start up and then settles in at 13.6 to 13.8  as we are on the road with running lights, A/C etc on.

                                                                                                                                                            Mike

[Edward Buker]

Looks like all systems go for lift off....

Later Ed

[Sean Donohue]

What time does Happy hour start? When does it end... I have notice that Happy hour is any hour not at work.

[Mike Merchant]

We find that Happy Hour varies depending on circumstances. For instance, in this case it was about 6pm sitting in our folding chairs on the shoulder of I-80 watching 50 miles of desert to the horizon while having a G&T and checking on the young lad who was installing our shiny new alternator. Sandy made him a sandwich when he finished up about 7:30 and he was thankful, tho that was not reflected in the bill.
                                                                                    Mike