Voltage gauge pegged red high

[bob69302]

Good evening all!
Make a long story short I did have a regulator problem. Well it was a piece of charcoal! I installed the new regulator and drove the truck for a couple days. The charging needle would stay just below the line in the green at 28.3 volts. So I figured let's drive it a lot (12 miles). All of a sudden the charging needle pegged Past the red high charging zone of the gauge. I pulled over and both batteries where hissing and boiling over. I would guess the needle was pegged for about 2 minutes of driving (less then 5 for sure). Both batteries are brand new and two days later both have a solid charge and load test good at 725 amp.

I disconnected the trigger line from the alternator and was able to drive it home on battery power.

Question: where to start!? What could cause the gauge to to sky high? Please forgive me, I don't know the exact voltage while the needle is pegged, I don't want to start it again and risk damaging components.

Thank you all again
Phil

 

[Retiredwarhorses]

Simple....the regulator failed. It's ok to start the truck to at least get an output reading, but did you attempt to turn down the output?...remove the Allen head and a screw driver to see if it will adjust.

 

[NDT]

Personally, I wouldn't risk hooking it back up. Once electronics screws up like that, it will either do it again immediately or do it later randomly. Each time you risk frying expensive components.

 

[wsucougarx]

I was having the same issue and narrowed it down to a faulty regulator.

 

[bob69302]

Well that's not what I wanted to hear. Its a brand new regulator! Oh well, someone has to get the bad factory parts! Thanks guys.

 

[bob69302]

Just an update. I turned the regulator down all the way. I was bouncing between 24 and 29 volts while the glow plugs were firing. After that stopped the voltage settled at 31.8. Just into the red on the gauge. Could the voltage be high because it's trying to charge the batteries that are low because I've been driving it on battery power alone? My thought is no... But i seek greater smarts!

 

[gcbennet]

Low batteries could wreak havok on the glow plug/ignition system if you're not careful. They should be removed and fully charged before engaging the truck's systems again so you don't inadvertantly fry something.

 

[Retiredwarhorses]

Just an update. I turned the regulator down all the way. I was bouncing between 24 and 29 volts while the glow plugs were firing. After that stopped the voltage settled at 31.8. Just into the red on the gauge. Could the voltage be high because it's trying to charge the batteries that are low because I've been driving it on battery power alone? My thought is no... But i seek greater smarts!

your bouncing is due most likely to your comtrol box type perfoiming after glow on the glow plugs for approx 1-2mins after startup. And No....31.8 volts is to high. It should be @ 27.5-28.5, just enough to get it into the white tick mark in the green zone....you regulator/gen is toast.

 

[gcbennet]

I had smoke pouring from my alternator (60 amp) so I metered the voltage. The factory setting is untouched from when I bought it (25v). I turned up the voltage slightly and the gauge needle would sit where it's supposed to for a few seconds then bounce between green and yellow. Sucks because this alt is less than 2 years old. Is this indicative of the regulator on its way out as well?

 

[Retiredwarhorses]

I had smoke pouring from my alternator (60 amp) so I metered the voltage. The factory setting is untouched from when I bought it (25v). I turned up the voltage slightly and the gauge needle would sit where it's supposed to for a few seconds then bounce between green and yellow. Sucks because this alt is less than 2 years old. Is this indicative of the regulator on its way out as well?

yea, smoke pouring from the Generator is perfectly normal....carry on.

 

[gcbennet]

The cooked unit is getting replaced, but my concern is if the failure was caused by something other than the regulator merely giving out prematurely or is there something, somewhere in the system that may be putting undo stress on the unit.

 

[papakb]

Everybody suspects the regulators, replaces them and then wonders why the new one fails. Whenever you open up the alternator always check the brushes and the brush holder. I've had the brush holders melt and when that happens the brushes made poor (or no) contact with the rotor field contacts and the voltage wanders all over the place. The same happens when they wear out. Brushes are cheap insurance, at about $5 a set if you don't replace them when you replace the alternator your asking for trouble. Almost any generator/starter shop can get them for you or you can order them directly from Southern Automotive, the people who now have the contract for the military alternators.

They themselves say they replace around 60,000 alternators annually which makes me wonder if a redesign isn't in order. Nothing should fail that badly without some investigation. But then again, it's a breadwinner for them.

Kurt
KG6KMJ