The International Cessna^® 170 Association

An A&P friend of mine was telling me that he had been having some electrical trouble with his 172, and traced it to having a too-low system voltage. It was around 12 point something with the engine running. He adjusted the "vibrator" type regulator to produce a reading of 13.5 or so volts, and that took care of the trouble.
I have a 60 amp alternator on my ragwing. My hard-wired GPS sez I'm only seeing around 12.4 volts. Although it's not giving me trouble, I thought I might readjust the regulator to get mid-13 volt readings. I opened up the regulator and lo & behold, it's all solid state! It's a Cessna p/n C611001-0201, made by Auxilec, Inc , mfr p/n VR600. It does have one solid state component inside there with an adjustment screw on it, but I thought I'd ask the forum about what I want to see for system voltages before I mess with it.
BTW, what brought this whole subject up with my friend,was that I had been having trouble lately with the starter turning the engine over very slowly. I charged the battery, checked the battery/starter connections, and checked the contacts in the starter switch (mounted on the starter)-- all OK. Turned out that 2 of the 4 brushes in the starter (the 2 you can't see very well with the starter still on the engine) were worn down to a nub! The other 2 looked great. I had a local auto-electric shop replace those 2 brushes for $15 (while I waited), now it spins 'er right over. So keep that in mind if your starting seems like it isn't up to snuff.
So what system voltage do I want to see?

Eric

Eric:

You want to see between 13.8 aznd 14.1 volts. I prefer closer to 13.8 to minimize heating the water in the battery. Regardless, don't trust the voltage indication of your GPS. Get a GOOD RELIABLE volt meter and check the voltage at the buss during cruise opperation.

Dale Faux

Eric
Dale is right about what you want to see.

Your GPS is probably accurate but I'd double check it to eliminate any possibility of a bad reading.

Since you've found your starter problem and have fixed it I could assume that you are having no other problem and perhaps are looking for something to be wrong.

I'd monitor your voltage throughout a flight. If it never gets higher than 12.4 then it is a little low. But if your having no problem don't break something trying to fix a problem you don't have.

Careful, there Eric! Either Paul Wood is posing as Dale Faux (pardon the pun) ... or Dale is lost and in Booneville Texas and being foxxy about it!
Seriously, if your GPS is actually hardwired to the electrical buss...then there might be some excessive resistance somewhere in the circuit between the connection point and the main buss and/or alternator. Generally the GPS voltage readouts are "digital" and therefore should be pretty accurate.... so that leads me to believe there's a high-resistance connection ...OR... the GPS is connected commonly with another high-current-draw accessory that is dropping local voltage. (Another possibility is an alternator with failed diodes, but that should manifest itself with "flickering" lighting at idle speed, or a "nervous" analog gauge.)
Try to obtain a voltage reading from the main buss somewhere and also checking connections between the alternator and the main buss.

Bruce is right in that I'm trying to fix something that isn't broken. Another way to look at this, however, is that I'm trying to avoid future problems.
Yeah, George, the GPS is hardwired to the buss via a half-amp circuit breaker. I kinda remember seeing 13-point-something readiongs in the past. I've had "voltage" set up as one of the datafields on one of the GPS's pages. But it hasn't been something I've been real on top of monitoring.
I don't get George's joke about you, Dale, but thanks for the voltage info. 13.8-14.1, that's what I was looking for. I thought you were a ragwing guy, but it looks you've gone over to the B model dark side.....

Eric