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#1
10-20-2008, 11:10 AM
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System Over Charging
I just replaced the battery in my 70 GTO with a new one, and I thought it was leaking so I took it back to the dealer and it was ok, turns out my car is over charging the battery causing it to boil/spill over. The car is putting out 17.8 Volts at idle. What area should I look at, the voltage regulator or alternator? This car still has the external voltage regulator on the firewall. I'm guessing regulator, but I don't just want to throw parts at it. Thanks
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#2
10-20-2008, 11:19 AM
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Yup, Regulator.
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Derek B. Current best: 11.97@110 1.65-60' !!! '74 ventura,  (Fired july 14/06) '74 462 4-bolt (9.5-1), SCAT, Ross, T-II w/850DP (shaker455), TH350, Conti 10'' 3800, Supercomps, Magnaflow, 3'' Pypes, 3.73's, 28x13.5-15 ET streets.1970 Beismeyer 17' flatbottom vdrive, 11.8:1 455P, ported heads, dual Qjet tunnel ram. 
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#3
10-20-2008, 12:05 PM
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Sounds like the regulator but make sure it has a good ground because a bad ground to the regulator will cause it to overcharge also. I run a test ground wire from the battery to the regulator base to test for this. Unplug the regulator and make sure it quits charging. If it is still charging at 17 + volts with the regulator unplugged, then it sounds like you have the alternator field wire melted into the battery wire. Probably just the regulator though.
You can double check the wiring at the regulator plug by unplugging the regulator and checking the wires for power with a test light. Two wires on one end should be hot with the key on and two at the other end should have no power on them until the regulator is plugged in. The wiring arrangement in the regulator plug is from one end to the other, 1. ignition wire from idiot light. 2. hot wire from battery. 3. stator wire from alternator[used to backfeed power to turn off the idiot light]. 4. field wire[this is a blue wire that the regulator uses to control the alternator. The regulator feeds power out this wire to the alternators field terminal which in turn causes the alternator to charge.] These numbers above are strickly for this post and do not reflect numbers that may be on your regulator. Sorry about the fine details but sometimes it helps to know whats what so you can make a good diagnosis without wasting money on parts you may not need.
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Paul Carter Carter Cryogenics www.cartercryo.com 520-409-7236 Koerner Racing Engines You killed it, We build it! 520-294-5758 64 GTO, under re-construction, 412 CID, also under construction. 87 S-10 Pickup, 321,000 miles 99Monte Carlo, 293,000 miles 86 Bronco, 218,000 miles |
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#4
10-21-2008, 01:31 AM
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Did it do the same with the old battery? Reason I ask is a bad cell can cause the alternator to overcharge too. Just had that exact issue with a forklift at work last month. If it didn't do it before, I'd suspect the battery, regardless if it is new or not.
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Darren P. '69 Firebird 461/th400/3.36/4wdb/Midnight Green Sold '64 El Camino, 468/Super T-10/9"/4wdb/eternal project '05 Springer Classic '07 Solstice GXP, wife's car |
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#5
10-21-2008, 02:06 AM
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Quote:
Occasionally on hot wire terminal (2), low voltage from a loose terminal, bad wire, or corroded connection somewhere, regulator thinks battery is dead/weak and will make the alternator overcharge. |
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#6
10-22-2008, 08:13 PM
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You need to fix this problem. There's enough power in an alternator to cause an electrical fire caused from a bad regulator.
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