Hey guys. I've had this problem for a few weeks now. And no one seems to have a solution.

Bearings in my old alt were totally shot. So i bought a new one. Charging worked with the old one. Put the new one in. And i get only bat voltage.

Figure it could be bad bat wires, change all of those. Checked the grounds between bat-ground and alt-ground. All that is good.

Figured it could be a bad alt from the factory. Get a 2nd one, same with that one. Even had the 2nd one tested in a bench. Works fine.

Yesterday i checked the voltage on the 3 wires that go in to the alt.
S = 12v constant
F = 12v with ign in on pos
L = no voltage in any pos

I have an 87 iroc z28 wich has no bat light. But has a volt meter. L seems to go to the volt meter. Funny thing is. The volt meter works.

Anyone have any idea whats wrong with this thing. Really want to go out driving now!

Alt is a cs130 delco

Greets from sweden!

 

as a gustaf, i cannot let a swede's request go ignored.

did one of the cables you replaced have a fusible link? if not you may want to check that cable.

additionally, there is an alternator circuit voltage drop test you can perform to test resistance. with a multimeter, touch one lead to the battery positive post, and the other lead to the bat + terminal on the alternator (the power wire post). You want something less than 0.2v (+v or -v reading doesn't matter, just depends on which lead you touched to which). try it idling and under load. something like 2000rpm with accessories on would be under load.
the other half of the test is one lead on the battery negative terminal, and one lead on the alternator casing (the metal of the alternator body itself). again, I believe it's less than 0.2v you desire.

btw, how do you know the alternator isn't charging?

of course there is also the belt tension (slipping belt) and condition of the battery to consider.

~good luck

 

Cool

Did not replace any fusable link cables.
Resistances are good.
I know the alt is not charging cause i checked it. Bat + on the alt and ground when it was running. Got 12.5v out from the alt. The volt gauge in the car reads the same.

Tested alot of things. But it feels like it should be something to do with the L connection on the alt.
Would be easy if it was a blown fuse or bulb on that wire. But i can't find anything.

 

Found a pretty odd thing today, I looked at the back side of the fuse box under the driver side dash and noticed that there's a brown wire going into the cooling fan fuse pin and the terminal on the other side of the fuse has no wire connected, essentially making the fan fuse a broken circuit. the previous owner did have the fan wired to constantly run so maybe this is why he did that. there's an aftermarket alarm installed like spaghetti in there so its possible they ripped the wire out when installing that, causing the previous owner to just hard wire the fan.

any idea what color wire is supposed to connect to the opposite side of the fuse?


whoops left this open in a tab and thought it was my thread I created yesterday, sorry for the weird bump

 

The L alternator wire requires a resistance feed to that L terminal.. use a jumper wire with a 50 ohm resistor or a dash light bulb and see if the alternator charges.. can be the connector , corroded wire or a fuse .. connections under the dash .

 

The L (lamp) terminal isn't powered unless a dash Volts light is used. Not unusual to not have voltage on it with a dash gauge.

The S (Sense) terminal is connected to a fusible link at the starter, This keeps the system voltage at the proper level.

The F (Field) terminal is what tells the alternator to charge (in this case). It has an internal resistor over to the L terminal. So with no power to L then alternator will still charge.

For a quick test unplug that connector from the alternator. Connect a wire from the connector S terminal to the alternator F terminal. The alternator should charge (higher voltage). If not then it is bad.

If it does charge then run a jumper from F to F (connector to alternator). If it doesn't charge then measure the voltage on that jumper. If not at battery voltage then something is wrong with the wiring.

If it does charge I would suspect that the connector is bad.

RBob.

 

the alternator output should be 14 volt range , if very cold like zero F it maybe 15volts .. winter cold temps should be in the 14 volts ..
the alternator at idle and no acc on or head lights should be 15-20amps .. then put head lights on voltage should not change stay solid .
12.5volts on battery means battery is good .

 

Dates. Y'all posting in a necro thread.