What would cause my alternator gauge to peg?

[MadScientist]

Hi all,

Im driving back home from a friends house and noticed about 1/2 mile from home that my alternator needle pegged at +20 and after arriving at home and disconnecting the battery, I noticed my ground cable on the alternator had melted insulation.  Would a bad voltage regulator cause this?

Im running electronic ignition and have all new harnesses for the dash/bulkhead/engine compartment, so I dont htink I have any  ground faults anywhere.

Any ideas on where to start looking for the problem?

Thanks

MS

[440fan]

Check your regulator and also all your grounds and that also includes the ground wire in your distributor.

[471_Magnum]

A pegged amp meter is usually followed by the snap, crackle and pop of a dash or engine harness cooking. Scary stuff.

[bakerhillpins]

A pegged amp meter is usually followed by the snap, crackle and pop of a dash or engine harness cooking. Scary stuff.

Are you sure he was reading an amp meter? He didn't specify the vehicle and most cars don't have amp meters on bats, rather volt meters. 20 amps is way low for an average car load anyhow. 4 55watt headlight bulbs draw close to 18.5 amps on their own. 2 bulb high beams draw less but add in the computer, luxury systems and whatnot and you are pulling way more than that for an average load. (yes that would be on modern car)

If it pegged at over 20 and your talking Volts then your reg is toast and its killing your battery at the same time. You shouldn't be dumping more than 14.5 or so volts into a battery for charging.

Bryan

[RAC95054]

Hi all,

Im driving back home from a friends house and noticed about 1/2 mile from home that my alternator needle pegged at +20 and after arriving at home and disconnecting the battery, I noticed my ground cable on the alternator had melted insulation.  Would a bad voltage regulator cause this?

Im running electronic ignition and have all new harnesses for the dash/bulkhead/engine compartment, so I dont htink I have any  ground faults anywhere.

Any ideas on where to start looking for the problem?

Thanks

MS

This happened to be before and it ended up being the insulator on the main alternator terminal getting cracked, coming loose, then it becoming a dead short.  It luckily fried my fusible link before taking out the dash harness.  Just about everything else is on a fise, except that, so I'd start there.
-Russ

[62 Max]

If you want to save your wiring from a short in the alternator,take a two inch piece of fuse link,put a male/female terminal on the ends and plug it into the alternator and then the field wire into that.It will go before there is any damage to the harness.