is15bbe@gt-oscar.UUCP (GT1295B MCCORMICK) (02/06/86)
I have a '69 Plymouth Belvedere. The voltage has been high
since I bought it. (About 16-18 volts)
Finally the battery died from overcharging. I replaced the battery and
had the electrical system checked. I was told I had a bad alternator. I
replaced the alternator, as well as the voltage regulator, for good
measure. The voltage was down to about 13-14 volts for 5 minutes, then
back up.
I took everything back to a local automotive electrical shop (ACE) and
was told the new regulator was just fine, but my new voltage regulator was
bad. I replaced the voltage regulator (again) and the same thing
happened. I worked all right for about 5 minutes, then the voltage
rose to 17-18 volts.
I know my voltage readings are correct because I've double-checked my
installed gauges with my multimeter.
I'd appreciate ANY help in this matter.
---
US SNAIL: William B. McCormick
P.O. 31295
GA TECH
Atlanta, GA 30332
...!{akgua,allegra,amd,hplabs,ihnp4,seismo,ut-ngp}!gatech!gt-oscar!is15bbeccrse@ucdavis.UUCP (Steve Ehrhardt) (02/07/86)
> I have a '69 Plymouth Belvedere. The voltage has been high > since I bought it. (About 16-18 volts) > > Finally the battery died from overcharging. I replaced the battery and > had the electrical system checked. I was told I had a bad alternator. I > replaced the alternator, as well as the voltage regulator, for good > measure. The voltage was down to about 13-14 volts for 5 minutes, then > back up. > > I took everything back to a local automotive electrical shop (ACE) and > was told the new regulator was just fine, but my new voltage regulator was > bad. I replaced the voltage regulator (again) and the same thing > happened. I worked all right for about 5 minutes, then the voltage > rose to 17-18 volts. One of my two '61 Valiants had a similar problem for years - it used to eat *at least* one voltage regulator per year, and it wasn't exactly gentle to batteries either! Since you seem to have already pretty much confirmed that the obvious parts of the electrical system (alternator, regulator and battery) are OK, there are a couple of less obvious things that you might want to check out. First of all, disconnect the hot lead at the regulator and use your VOM to check the voltage at that point. If it is significantly lower than the voltage at the battery, then whatever is causing the voltage drop is probably the culprit. Unfortunately, finding the source of the resistance may be difficult, but the ignition switch would be one thing to check. Secondly, check to see if your regulator is well grounded. If it's typical of how Chrysler used to do their regulators, it will be grounded through its base to the chassis, so check for corosion there. Also check for missing/ lose ground straps from engine to chassis and the like. The easiest way to check may be to run a wire from the negative pole of the battery to the base of the regulator and see if the problem goes away. A factory shop manual can give you more exact testing procedures and what voltage drops would be acceptable in both cases. In my case I found that I had both a bad ground *and* a bad ignition switch, and I have had no further problems since correcting them. Good luck!
bruce@dciem.UUCP (Bruce Ferguson) (02/17/86)
At one time I had a similar problem on my 1971 Volvo (similar regulator & Motorola alternator). It drove me nuts because it defied (superficially, anyway) all that made sense. However, there is an explanation for all observed phenomena, (least there is since I stopped taking them wee pills) and it turned out that the reference voltage that the regulator was seeing was lower than the voltage coming from the alternator because corrosion had "necked-down" the sense wire (right at a crimp-lug) and was dropping a couple of volts by the time the regulator saw it. The regulator (via the field or control output) was just doing its job in trying to regulate field current to produce 14.2 volts (factory regulator setting at 20C.), at its sense input. To supply current to the field winding, and to function as a regulator, the current supply to the regulator can be as much as , say 5 amps. It must therefore have connection to B+ on the alternator or battery, of no less than about no.16 wire . It is also important that both the alternator, and the regulator are grounded properly or the same thing can happen, they "float". In older cars, corrosion can introduce strange gremlins in the electrical systems. I once had a friend with an old Volvo, that when cold, would power the high-beams when asked for low-beams (indicator off), and then switch over to the low-beams, (indicator off), after about 20 minutes. Good Luck