Alternator

[4x4grey88]

My alternator at idle gives 12.1v and at 2000 rpms goes to 13.7
My problem is that my batteries went down to 8.9v and would not start. The batteries are only 4 months old. I can't find any short nor did I leave anything on while parked.

The same thing happened four months ago and I thought the batteries were bad, so I changed them. Have not had any issues after installing the new batteries - until now.

Any input???

 

[Friis]

Is the problem evident immediately after driving, or after the truck has been standing for awhile?

 

[DaveBen]

You should see 14V+ at 2000 rpms or your batteries will go dead after a while. Drive your truck more often if possible. See if this helps or not. I would expect it will not and you will need a new alternator.

Dave

 

[4x4grey88]

Well it did it again. everything seems fine while, engine is running. This morning the batteries are reading 8.9v, no start, just clicking. Jumped the batteries (after a while) and the engine started. Alternator reads 13.0v (at 2000 rpms).
I put my meter on amps and put it on the red wire from the alternator. It read 8.7 amps. If my batteries were dead and I am only seeing 8.7 amps draw I'm thinking its time to replace the alternator. It read 32A while trying to start the engine.

The batteries were installed new in July and I am not finding transient power drop anywhere.


I have been looking (auto parts) store and can't decide if I should get a 110A or 140A alternator. I have seen 200A alternators advertised too but don't really think I want to go that high.

 

[DaveBen]

I would go with the alternator with the most capacity that you can reasonably afford. I will go with a 200 amp model when it comes time. Good luck!

Dave

 

[4x4grey88]

I installed a new alternator and it charges fine now. I only got the 110A alternator from Kriagen Auto parts. Life time warrenty.


Next comes my "blue spring" intallation.

 

[jherman]

yeah i had the same problem and i went through 2 Kragens alt's before i bought the good one from the guys in detroit and i dont think i will have problems for along time.

 

[BIG JOE]

yeah i had the same problem and i went through 2 Kragens alt's before i bought the good one from the guys in detroit and i dont think i will have problems for along time.

I hear ya on the "Lifetime Warrenty" Alternators. They'l be Free.. but yul be changing'm out.. for a "Lifetime". (not to mention what it does to batteries)

A good pair of 600+ CCA batteries, a 160+ Amp replacement Alternator... yul be Good To Go.. for a.. "Lifetime".

Joe

 

[Hillbilly hotrod]

I bought a 200amp alternator off ebay for 160. Works great with no issues.

 

[NJKen]

be careful with the higher than stock output alternators. Some of them dont really make any usable power untill higher RPMs. An example would be a stock alternator rated at 130a will make about 90a at idle and reach full output by 1300rpm. an aftermarket high output model will mag 50a at idle and reach its rated output at around 2000rpm. If you idle a lot like I do (its a bucket truck) you will wind up with dead batteries fast. Ask me how I know this! Been there, done that...
Ken