Charging at 15 Volts

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jhdeval

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My car is suddenly charging at 15 Volts. It had been at 14.4 prior to this. What can cause a high charging voltage? Maybe a made voltage regulator?
 
clean your bulkhead connections.
may have too much voltage drop and low voltage at the coil.
volt reg senses this at the run side of your ballast
..just a thought.
 
ir3333 I actually have cleaned the connectors. Got in there with a toothbrush and brake cleaner. Then the wife killed me when I cut up her emory board lol.
 
jhdeval said:
OwdKasd How can I check voltage drop at the Alternator?
Click to expand...
Just check for battery voltage at the field wire (Key in run position). The less it is compared to battery voltage, them more it will charge. ie: if the field wire shows 11.5 volts and the Battery is at 12.5 volts than the alt. will put out one extra volt when running. If you have 2 field wires you can check them both the same way just use the positive battery terminal for checking the + field wire and Visa-Versa.
 
JH, you checking this with key in run, engine off? IF so you have a LOT of drop

Here's the basic bath

From the battery -- fuse link -- through bulkhead -- ammeter circuit -- in harness splice -- to IGN switch connector -- through switch -- back out switch connector (on dark blue "run") -- back out bulkhead --

to IGN run buss, which feeds

"key" side of ballast resistor and regulator "IGN" terminal

On 70/ later cars, it also feeds

alternator field (blue)
electric choke if used
some smod doo dads

ANY bad connection in that circuit path I mentioned with ADD that much to the charging voltage, because the regulator "thinks" the battery is low

To do a "quick" check to see if you are on the right track, make up a nice big no14 or so clip lead. Hook one end to a "solid" battery point such as the stud on the starter relay

Hook the other end to the regulator IGN terminal. If the voltage settles down, you need to check that path I mentioned.

If not then DOUBLE check

With the clip lead hooked up, and engine off, measure voltage at the reg. IGN terminal compared to battery

You can do this directly, by putting one meter probe on the regulator "I" terminal, the other probe onto battery postive. You are hoping for a very LOW reading, the lower the better, and not over .2-.3V (that's 3 TENTHS of one volt)

If this is so, then start the car and running at a good fast RPM to simulate "medium cruise" measure between the regulator mounting frame and the battery NEG terminal. Again, you should read a very low reading, zero is perfect.

If the above is true, replace the regulator and recheck.
 
Turns out the ignition side (bottom) connector on the voltage regulator was severally corroded. I cut it and replaced it and now I am charging at 14.1-14.2 which I understand is a good voltage for charging.
 
My alternator puts out 15 volts at idle, but this didn't raise any concerns on the forum here when I posed the question. My problem was that I was losing voltage at the bulkhead connector and who knows where else, so that the charge at the battery was only 13.3 volts. I did the MAD bypass and now have no loss of charging. I now get 15 volts at the alternator and 15 volts at the battery.
 
Well, the thing is, 15 volts is too much.

What are you running for alternator / regulator?

The very first thing is to check if the regulator is operationally grounded, and if the sensing voltage IE the ignition voltage supplied to the regulator is "same as battery."

If the two above items are OK, test the battery, and if it checks out, replace the regulator with a good quality one.

SO once again..............

Turn the key to "run" engine off. Hook one probe of your meter to the regulator "IGN" terminal, and the other to battery POS post. You are hoping for a very LOW reading, and in no case, more than .2-.3V (3 TENTHS of one volt) ANY voltage in this path ADDS to regulator charging voltage setpoint

Check the ground. With engine running, and charging at an RPM to simulate "medium cruise," stick one probe on the battery NEG post, and the other directly onto the regulator mounting flange.

Once again, you want to see very low voltage, zero would be perfect.
 
One other place voltage drop can manifest is at the battery terminals, and negative battery to ground connection on block, so recheck them, and clean if necessary. All the stuff 67dart273 said is correct, but don’t discount possible voltage drop in the ground path side of the ignition & charging circuits.

Alternator, spark controller (orange box type device), and voltage regulator’s, outer cases have to have a good voltage drop free connection to body of car. If you detect voltage drop at any of these devices by placing black VOM probe on negative battery terminal, and the other probe on the base (chasses) of the above three devices, and there is any voltage reading, say 0.05v or more you need to correct it.

One way to correct for ground side voltage drop is to make a ground loop out of #14 wire with crimped eyes that loops around connecting to voltage regulator, spark controller, alternator attached to one each of their mounting screws, and back to negative battery terminal. By making this loop you eliminate poor connections to sheet metal, and multiple crappie ground path connections through body and engine block.
 
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