voltage regulator

[jrohr]

After doing LOTS of searching on this site, I have a couple of questions pertaining to the voltage regulator. One post I read said to test the regulator by checking voltage at the field wire with the key on. Question: Exactly what part of the regulator is the field wire?

If I am checking correctly, I have about 12.5 volts at battery. With key on, I get the same reading at the alternator, but no reading at the regulator. With the engine running, the reading is about 13.55 volts at the regulator, as well as at the cigarette lighter. I do get a reading at the regulator with the car running. Does this point to a bad regulator?

Thanks

[gr_diver]

A very rough method to test your regulator: after the car has sat overnight, or for several hours at least, start the engine and immediately measure the voltage at the battery (no accessories working). It should be ~14V, or higher, but less than 14.5V. Anything over 14.5V suggests a faulty regulator.

After driving around for a little while (e.g. 20mins), and with the engine running measure the voltage at the battery again (no accessories working). This time it should be ~13.8V (+- 0.2) or at least less than the previous voltage. This would mean that when the battery got re-charged the regulator backed-off, to prevent over-charging/ boiling of the electrolyte... Anything less than 13.5 should make you search more. If the voltage increases if you rev the engine, your idle speed might be set too low. If the low voltage does not increase with revs, then probably the regulator is faulty... You can try "pressing" the brush-holder a little (watch your fingers being close to the fan belt!), if the voltage increases then the brushes need replacement.

I am sure the other friends here will help you with the specific troubleshooting information you asked for, but I thought I would post this quick-n-easy amateurish method...

[namba209]

Another quick and dirty way to see if the alternator/regulator is working, is to have the engine running at idle, turn on the headlights, look at the ammeter, then run the engine to about 1700 RPM and see if the ammeter goes to the plus side of the gage. Make sure you do have an ammeter lite on with the key on and engine not running, and that it goes out with the engine running. If the bulb is burned out, the charging system will not work. BTW, normal charging rate should be 13.8V-14.2V, your reading of 13.55V indicates the system is charging and the battery may be close to being fully charged, if everythng is working normally. HTH.

[gr_diver]

Oops! I forgot that the GTs have an ammeter as well. That's surely an easier way to see what's going on, than my method. I only have a voltage gauge, and it is quite inaccurate, that's why I prefer measuring directly at the battery with a DMM...