Alternator

[B-17]

Has any one had this problem, i remove my old alternator - currently when driving batt indercator shows 14 - 14.5 so defo charging - replace with new one sits at 12.5 no charging/movment of batt needle i have now tried this with three alternators and no joy, replace old one and 14 - 14.5 again on dash gauge.

Now, is it safe to run the batt wire on the back of the alternator drectly to the + batt post to by pass my wiring to see if it charges that way, or will my rod go up in a flash of flame........:D:confused:

[stueeee]

What make/model of alternator(s) have you been using? the regulator types often vary in apparently identical yank alternators.

Stuart.

[B-17]

Stueee

Thay are all Yank ones, chrome, two the same and one off a chevy motor which is slightly diffrent.

Thay are all roughly the same to power my SBC.

[stueeee]

Stueee

Thay are all Yank ones, chrome, two the same and one off a chevy motor which is slightly diffrent.

Thay are all roughly the same to power my SBC.

Ok, what wires have you got connected to your alternator? Just the batt connection, or have you got any other connections made?

Some of the chrome Delco lookalike alternators will work as one wire (batt) or three wire (batt, field & sense) by removing a small plastic link on the back edge of the alty which reveals the other two lucar connectors, this wiring trick won't work on a lot of genuine Delco (Chevy) alternators though.

Stuart.

[B-17]

Stuart

2 wires, the normal One Batt+ lead and a thiner wire from one of the two spade conectors that sit together under the black cap.

http://images.channeladvisor.com/Sell/SSProfiles/13000024/Images/5/10SIY%20CH%20BACK.JPG

[stueeee]

A thin wire needs to be connected to the No. 2 terminal and should have 12V Positive on it when the ignition is turned on. This is the sensing terminal that allows alternators to set the charging voltage correctly.

Older genuine Delco alternators also need a connection to the No. 1 terminal from the ignition switch, this is the field circuit where the warning light would go if your car has one.

Stuart.

[adey]

you should also be able to remove the black rubber cap, and have a 3 wire configuration also.

[B-17]

A thin wire needs to be connected to the No. 2 terminal and should have 12V Positive on it when the ignition is turned on. This is the sensing terminal that allows alternators to set the charging voltage correctly.

Older genuine Delco alternators also need a connection to the No. 1 terminal from the ignition switch, this is the field circuit where the warning light would go if your car has one.

Stuart.

Ok Stuart, my thin wire is in number 1 terminal, are you saying if i fit a 3rd wire from terminal 2 directly to the main + wire on alternator - by splicing in the new wire to my current alternator main wire - this should work, if so could i set up a short cut by running a wire from terminal two and alternator +post to main battry + post to see if it works before i cut in to the main wire.


Thanks for your advice.

[stueeee]

Ok Stuart, my thin wire is in number 1 terminal, are you saying if i fit a 3rd wire from terminal 2 directly to the main + wire on alternator - by splicing in the new wire to my current alternator main wire - this should work, if so could i set up a short cut by running a wire from terminal two and alternator +post to main battry + post to see if it works before i cut in to the main wire.


Thanks for your advice.

Yes if the alternator is good that'll work. A bit more detail below if you're interested.

If your alternator has a late type regulator, connecting teminal 2 (sensing) to 12V positive (the batt connection on the alty will do fine fine for this)then it'll work straightaway. No other connections needed

If your alternator has an early type regulator it needs the sensing connection as above, and a connection from terminal 1 (the field connection) to the switched ignition, via a warning light if you have one.

Don't be tempted to connect the field connection to an unswitched 12v positive without a diode in the circuit, or you'll find that your car keeps running when you turn off the ignition; this is because of a condition called backfeed caused by the unswitched field connection.

Stuart.

[B-17]

Thanks for all that very usefull stuff have rigged a wire from term 2 to main feed on alternator and dash batt gauge showing 14 - 14.5 ish so i think i maybe there, only one thing know dash/ignition light from term 1 stays on and is very bright wile engine is running :confused: would it be safe two swap them both round and see what happends.

[stueeee]

dash/ignition light from term 1 stays on and is very bright wile engine is running :confused: would it be safe two swap them both round and see what happends.

If the wires are correctly connected now, swapping them will mean that the motor will keep running when you turn off the ignition, and you may find that your charging voltage goes up beyond 15V too.

If you pull off the wire from terminal 1 with the ignition turned on but the motor not running, does the warning light go out? if it does, and the light comes on again when you touch the terminal 1 wire to ground, I would suspect that you have a faulty regulator. If those two things don't happen, you have a wiring fault.

Stuart.

[B-17]

Ahgggggggggggg.......... have now tried three alternators all the same, on tick over the bat gauge shows its not charging - 12.5ish but no light comes on- so you have to rev it a little and it seems to jump up to 14ish volts as if charging but then dash light comes on then.Volt meater at battery shows the same 12.5 then 14ish.:confused::confused::confused::confused::con fused::confused:

My car hasent got just ignition on. engine its push button starter, no ignition key.
Thanks again.

[stueeee]

My car hasent got just ignition on. engine its push button starter, no ignition key.
Thanks again.

Whatever you have instead of a key, unless your car has magneto ignition, before you can start it, you must have 12V going to the ignition or you wouldn't be able to start the car. Also when you stop the motor, you must be removing the 12V somehow.



on tick over the bat gauge shows its not charging - 12.5ish but no light comes on- so you have to rev it a little and it seems to jump up to 14ish volts as if charging but then dash light comes on then.Volt meater at battery shows the same 12.5 then 14ish.:confused::confused::confused::confused::con fused::confused:.

So what you're saying here is that the warning light is off when you first start the motor. It should be on because the 12v from your ignition should be going to ground via warning lamp, the wire and then the alternator field connection.

So you almost certainly have a wiring fault not an alternator fault. Try doing the two tests I put a few posts earlier -when you have the ignition on but without the motor running, the warning lamp should be on, if you pull the connection from No. 1 terminal, the light should go off, now touch the wire to ground and the lamp should light again, if it doesn't do these things, there isn't a good 12v at the ignition end of the field wire and no amount of changing out of alternators will fix the problem until you sort the wiring fault you have on the car.

HTH, Stuart.