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gatorv · 11-10-2013, 09:37 AM

My alternator is putting out about 14.7 volts at idle and the dash gage is almost pegged.
An old trucker in the RV park told me there is a voltage adjustment on the back of the alternator. Anyone ever heard of that? Is that to much output? Thanks in advance.

Gator

EngineerMike · 11-10-2013, 10:34 AM

The old trucker may have been right about an old alternator.
Assuming this is something new (and you had ~14.0 steady before), sounds like your alternator is going out. Have it tested at a local shop or parts house. If you have it rebuilt, have the shop put the diode pack on the outside for better heat dissipation.

Dave Fernandez · 11-10-2013, 11:37 AM

Gator I would go from a 160 amp alternator (Standard) to a 200 amp alternator (Delco Remy 28SI 200 Amp Heavy Duty Alternator),

if I needed to replace the alternator since it is a bolt in and no alterations are needed.

Alternators use an internal voltage regulator if they start going out and the voltage increases they should be replace not adjusted. If there is an adjustment it is used when they are first installed and tested. When they start to change they are going bad. It will need to be replaced anyway.

palehorse89 · 11-10-2013, 01:16 PM

Gator, before replacing the alternator I would have your battery's checked, if one or all are going bad it will make the alternator charge at a high voltage. Take your batteries out and have them tested first, then if OK move onto the alternator.

YC1 · 11-10-2013, 01:36 PM

Ditto on cleaning up your battery posts and checking the batteries with a hydrometer. That voltage is not out of line. Not likely you have any adjustment on that late model RV. It has been a lot of years since I have seen a regulator adjustment.

Without getting technical, just doing decent maintenance will make gremlins like a meter pegging go away quite often.

Algoma · 11-10-2013, 04:17 PM

No one has mentioned the fact that these alternators have a remote sensor. The sense wire goes directly from the battery to the alternator and the regulator in the alternator adjusts the output to what it sees on this sense wire. It sounds as if your alternator is not getting a good reading on this sense wire and is outputting its max. regulated voltage. Poor connection on the +ve and gnd terminals and the sense terminal should be checked first but if they are good it may be that the alternator regulator is bad. I would get a new one rather than have the old one rebuilt if money is not an issue.

Dr4Film · 11-10-2013, 04:23 PM

14.7 VDC sounds pretty normal to me regarding adequate output voltage from an alternator. You don't need a new alternator as yet.

Your gauge is what's acting up. Check your ground wire to the gauge or run a temporary ground wire to see if it corrects the reading.

Dr4Film ----- Richard

clyon51 · 11-10-2013, 04:33 PM

Quote:

Originally Posted by Dr4Film

14.7 VDC sounds pretty normal to me regarding adequate output voltage from an alternator. You don't need a new alternator as yet.

Your gauge is what's acting up. Check your ground wire to the gauge or run a temporary ground wire to see if it corrects the reading.

Dr4Film ----- Richard

I tend to agree. My alt puts out 14.1 to 14.6v. I wouldn't panic at 14.7. But I would check the gauge, battery condition and connections.

Old Scout · 11-11-2013, 05:59 AM

The rebuilt alternator[4 years old] on our 03 puts out a fairly steady 14.8 to 14.9 on the center post of the battery isolator. Yet the chassis batteries read about 14.1 at idle to 13.8 with a heavy load [eg lights, fans, wipers, etc.]. The house bats stay in the mid to high 13's while driving. These readings are off the inverter display for the house and off both the anolog dash guage and a plug in digital display from CW for the chassis bats. Chassis bats are less than a year old and cable connections are clean.

Since this particular alternator is monitored??? by a remote controller/ sensor [4-post connection on alternator][name of controller escapes me at the moment]. I wonder if you have to consider whether the remote controller is working properly before replacing the alternator. I hate doing trouble-shooting/diagnostics with new parts but sometimes>>>>>>>

wa8yxm · 11-11-2013, 10:09 AM

Alternators come in 3 types for this discussion

One is designed to be used with a DIODE isolator and thus puts out a bit too much voltage.. GM seems to use these alot even if they do not use a diode alternator.

The other is designed to be hooked up without an isolator or via a solenoidd kind (slightly lower voltage)

The third kind is adjustable,, also rare

There is a 4th kind (even rarer) which uses an external voltage regulator. I've not seen one of those since last century.

Algoma · 11-11-2013, 12:56 PM

Allow me to totally disagree with the last comment. Externally regulated alternators are very common and used on marine engines and battery charging systems. See Balmar.
However it is true that you probably won't see these in RV's as they are expensive.

The remainder are either 3 terminal or 4 terminal. In a 3 terminal alternator (used mostly in cars) the internal regulator reads the voltage at the +ve output terminal and adjusts to that. If you use one of these with a diode isolator you will lose between 0.5 and 0.7 volts at the battery. To overcome this the 4 terminal alternator has a "sense" terminal that connects directly to the battery bypassing the diode isolator. The regulator adjusts the output of the alternator to the voltage on the sense terminal (not the +ve terminal) so the output voltage will be higher to compensate for the loss in the isolator. If you don't have an isolator but have a combining solenoid the alternator regulator will output a lower voltage as it does not have to compensate for the diode voltage drop. Either way they are exactly the same alternator.

gatorv · 11-12-2013, 07:34 PM

So far this is where I’m at. One house battery had dead cell and I replaced it, The others are due but no time now. Working ten straight then headed for Glamis. I cleaned the sense wire on the Alternator, Now I have 14.8 at battery isolator and 14.2 at batteries. The gage on the dash is definitely wrong. It reads 16 volts with the key on and engine not started. It will go on the on the retirement list. It’s a really big list. Anyway Thanks for all your help. Gator

Dr4Film · 11-12-2013, 08:21 PM

Quote:

Originally Posted by gatorv

So far this is where I’m at. One house battery had dead cell and I replaced it, The others are due but no time now.

Thanks for all your help. Gator

They say not to replace just one bad battery within a bank of them but your choice, time will tell.

Dr4Film ----- Richard

Old Scout · 11-13-2013, 06:26 AM

Agree with De4Film--appreciate your need to get on the road but depending on how long you run the new bat with the old bat bank, the old bats will probably kill the new bat. If you dont switch out the rest of the bank sooner rather than later, you will probably have to replace all the bats.