sublime8396
Registered User
So ive searched and searched and tried different fixs but still cand get it to charge at idle. New regulator fancy dual isolated alt from a fire truck. New napa alt new batteries and cables im lost any suggestions?
charging help
- Thread starter sublime8396
- Start date
So is most everyone else without knowing what year truck you have. Put it in your signature.
sublime8396
Registered User
Oh sorry its a 91 f250 7.3
Tell us more about the alternator. Is it supposed to be externally regulated? Is it a newer internally regulated piece? If it's internally regulated and you still have your external regulator I can't imagine it working well. Pics of it all would be helpful as well.
sublime8396
Registered User
I have lestek 9290df im not sure if its internal regulated or not actually. It used the same plug as the original alt just has two battery out puts that are bridged. It charges fine anything over 1000rpm. Im not sure how to post pictures yet but ill try to get some up
jim_22
Full Access Member
Are you sure it is not charging at all on idle? Putting your voltmeter on the battery will tell you immediately.
I've never seen anything like that. Are you sure your alternator is good? You might try unhooking one side or the other if it is truly isolated and you are bridging it for max current, maybe one side has something wrong with it and you aren't overcoming it until 1000 rpm. I'd guess it would charge some amount on one leg. Check with meter. You should get 13-14 V if it's charging. Right at 12 If it's not.
sublime8396
Registered User
Volt meter says 12.5/13 at idle and with engine off but if i rev it a bit it jumps up to 14.5. And the exact same thing with the napa alternator. .... so it has to be the harness right? I found a diagram for it so thinking about making a new harness to the regulator. The fire truck i got the big alt from had a wire from the bat terminal to the pos side of battery and my truck runs it back the harness to the hot side of the starter solenoid. But again it charges over 1000 rpm so that must be working ....ugh this is driving me nuts lol
Not sure exactly what you have a s far as your charging set up, but if it is relatively stock it will not charge well at idle. Converting to an internally regulated 3g alt can help improve this and reduce your failure rate.
On my '88 my voltage will vary at idle from the 11.8v range to 13.5v, depending on what load I have on the system. Mine is a van with front and rear AC. If both blowers are going it really pulls the voltage down. As soon as I take off the voltage jumps to the 13.8-14.8v range. If I have been driving long enough to charge the batteries well it will sit over 13v at idle with no load.
The stock charging systems on these vehicles are not that great. That is why people tend to upgrade to a 3g set-up if they are going to tax it at all with added components.
On my '88 my voltage will vary at idle from the 11.8v range to 13.5v, depending on what load I have on the system. Mine is a van with front and rear AC. If both blowers are going it really pulls the voltage down. As soon as I take off the voltage jumps to the 13.8-14.8v range. If I have been driving long enough to charge the batteries well it will sit over 13v at idle with no load.
The stock charging systems on these vehicles are not that great. That is why people tend to upgrade to a 3g set-up if they are going to tax it at all with added components.
icanfixall
Official GMM hand model
Look on the passenger side fender well. If you see a square can item about 3x3 with several wires feeding it then thats an external voltage regulator. Now usually an internal voltage regulator is found attacked to the back of our alternators that are internally regulated. Its a square grey box about 1 1/4x1 1/14.
That may be all you get. If it's over 12, it's charging albeit not much. Are there any loads drawing on your system you aren't thinking of? Blower motor? Radio? Random electronic thing?
If you need it to charge at idle and there is nothing else weird going on, the easy solution might be to bump your idle up a little or do the high idle mod.
If you need it to charge at idle and there is nothing else weird going on, the easy solution might be to bump your idle up a little or do the high idle mod.
those type alternators are built on a 1G frame and low idle output is normal.
i have always been under the impression that alternators have to be "excited" before it charges.
usually above 1500 rpms for it to kick on.
usually above 1500 rpms for it to kick on.
sublime8396
Registered User
I replaced tge voltage regulator and still same thing. My vw alt has to be excited by a quick rev but then charges this one even after a rev it drops back to nothing i had the alt tested and it passed everything both of them. I like the 135 amp alt but at this point i feel i would be better off putting in a gm one wire lol. Ive been tinkering alot getting this truck running good and not leaking but its rough when it always has to be a charger unless i take it out and drive it while working on it.
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