4 wire alternator wiring
 

I've got a replaced 4 wire, internally regulated alternaor. Where is the sensor wire supposed to be wired into? At the horn relay? My alternator is good, but sems to be only weakly charging the battery. The sensor wire is currently wired to the 12V output post directly. Thanks.
Gary

One of the members posted the following link in another thread. I couldn't find the thread, thanks to who ever posted it. The tech info at madelectrical is great. There are several articles, the link is to the remote voltage sensing article. Hope this helps :thumbs:

http://www.madelectrical.com/electri...esensing.shtml

on my '69 the sense wire is connected to the horn relay at the same place the big charge wire is attached.

This is also where I get all power from. I never take power from the battery, always from the horn relay terminal.

Are you sure the regulator is good? If not, you might consider a Ford solid-state regulator. It's an easy swap, you can use male spades and not cut the GM harness if you like.

I'm pretty sure the alternator is good. The ammeter shows it's charging. I'm just not getting a good charge to the battery. All connections are good and the battery checks out OK.
Gary

68 has an external regulator. I would take the alternator and have it tested. If it tests OK and the wiring is good, I would replace the regulator.

Update:
Load tester showed good battery. I moved the sensor wire to the horn relay.
I did notice that the ammeter (differential voltage meter) would occasionally flicker back and forth between + and -.
Battery vltage with no load was 12.5 V at both battery and horn relay. Running, with no load was 14.5 V. But when I turned on the headlights and radio, voltage dropped to 12.5 at the horn relay and battery.
Diagnosis? Intemittent diode (under load) in the alternator. Explains the ammeter flickering and weak charging.
Anyone else got any thoughts?
Gary

i posted that link and it seemed to say to me ....that you want it it to be further away and isolated....so if the horn isn't giving a good reading to the alternator then why not look for something that is not running off of a relay for example the cigarette lighter?

If the voltage drops under load, it's a bad alt or regulator.
Or maybe not sensing properly.
Measure the voltage at the sense wire of the alt, make sure it's that same as at the horn relay.

If not get a new alt ( or regulator )

My take is that you want the sense wire to be connected to whereever you take power from. If you sense here and take power from there, the alt will be putting out the wrong voltage.

I hooked a fused distribution block to the horn relay so all accessory power for the fans, MSD etc come from the horn relay. Things work much better now

....that you want it it to be further away and isolated....

Great idea.
Gary

iItmakes sense to me to have it hooked to a source that is under load at the time of the "sensing"...maybe the cigarettte lighter is a bad example....so then the horn would only be a good example for this "sensing" when blowing the horn and you have the load condition.

Actually,on the 68 at least, all load is distributed at the horn relay connections. It splits there to feed the ammeter/battery and the rest of the electrical.
Gary

i wonder if the battery would give a false indication since it has stored energy in it, as opposed to a source at the end of one of those circuits?
But i will be the first to admit, this discussion is pushing my knowledge of electrical stuff.

The voltage will only vary if there is resistance in a loaded circuit. I'm geting the same voltage throughout the circuit, loaded or not. 14.5V no load, 12.5V loaded. Since 12.5V is the same as the battery voltage alone, it kind of indicates the alternator is not up to the task of running the accessories.
BTW, just ordered a 100 Amp Chrome alternator from summit for $60 on special. I know, it's a one wire, but that was too good a price to pass up.
Gary

A 1-wire will eliminate the regulator from the circuit. That will help clean up your engine compartment too. Should be nice :thumbs:

Everything is a resistor, some are just better than others. :ack:

If your alt voltage drops under load then there is something wrong with the alt, I agree.

A one wire alt will kinda work and in a vette since the horn realy is so close to the alt it might not even matter ( at least on my '69 where they are both on the drivers side)

The only problem with a 1 wire is it senses internally rather than where the actual load is. so you will loose a little voltage ( but I'd bet that it's insignificant )

MOre important is probably to run a heavier wire from the alt to the Horn relay so there is negligable voltage drop

Good Idea. I think the original is 10g. I'll make it an 8g.
Gary