Is my alternator failing?

Don't go reman, usually those don't last as long. Look into the 28SI, 36SI and 40SI. 28SI is a brushed alternator up to 200 amps, personally I favor alternators with brushes because they run much cooler. 36SI and 40SI are "fuel efficient" models that can save hundreds of dollars per year in fuel. 36SI is 68% efficient and 40SI is 75% efficient. Take a look at this calculator:

http://www.delcoremy.com/Alternators/Fuel-Economy-Calculator.aspx

The 36SI and 40SI are quite large. If you want a smaller brushless alternator go with Bosch.

http://heavyduty.boschautoparts.com/AlternatorsAndStarters/Pages/LongHaulAlternators.aspx

Or the extreme long haul alternators:

http://heavyduty.boschautoparts.com/AlternatorsAndStarters/Pages/LongHaulExtremeAlternators.aspx

Bosch long haul are 68% efficient, extreme are 71-74% efficient. 36SI are 68% efficient, 40SI 75%. All of the above come with a 3 year/350k warranty except for the Bosch long haul (not extreme) come with a 2 year 250k warranty.

Does anyone know anything about leece-neville or Denso alternators? I know the latter are favored by a few but they have lower temperature ratings.

 

I prefer the delco alt they seem to be as reliable and cheaper. The batt do need to be fully charged to check them. Also they are not really die signed to charge a batt only maintain. 14.5 volts is ok but I wouldn't. Want any more. Most will charge a little diff but sounds like there are under lying issues causing it to over charge

 

Make sure you check the connection at the starter. Most trucks run the cables from the battery and the alternator to the starter post.

 

If you have 12 volt batterys, they are wired parallel, if 6 volts, they are two pairs in series to get you to 12 volts at the starter. Now the biggest issue is always CONNECTIONS, as stated before. If you want to get it right, the first time, clean and secure all connections meticulously.

 

Cheap multimeters can be had for less than $15 and will serve you well. A battery charger is also a must in your arsenal. My old Craftsman 2/10/50 amp does the job for me.

I don't know if the car parts stores alternator testing machines can take a big truck alternator but it's another idea for ya.

 

Heat can be a big deal especially if you have an EGR engine, you're using hotel loads, or the alternator has a heavy load.

Go with the Bosch, let us know how long it goes. Can't argue with that warranty.

 

Actually they are wired in parallel not series, but I knew what you meant. If the first + to + "jumper" is bad or has a bad connection, you will theoretically have one useable battery. Charging and drawing both, if the rest were installed fully charged, and the cable isn't up to par, they will "test" good both volts and load tests, because you have not drawn anything out or recharged them. They will still test good as new because they are. If they are connected with good cables they should be exactly the same, not within .2 or.3 volts.

 

Poor mans way of checking cables is get a helper, one at a time hook meter up to each pos and neg and start the truck all batteries should show and drop same amount whether it's no load or starter engaged. To check batteries they should be completely un hooked both sides, to check cables they must be hooked up just like they are used. To check main cables put leads on main hot at starter and ground. Take a no load reading then load reading. The no load should match batt. The load is allowed .2 volts drop due to length. Freight liner used to run main Grd cable to frame out of bat box then run eng Grd to frame. That's always where I found my bad connection if their was one. I have seen lots of alt replaced due to bad batteries poor connections or bad gauge. Keep in mind a bad connection and bad batteries are all hard on an alternator and shorten its life. Boosting the truck off and using alt to charge batt is worst thing for them.