Need Help with low voltage!!!

[AM86]

Battery reads at 12.5 not running (with a volt meter after a drive). Replaced altenator with a new pro-start 120amp from Pep Boys. Made sure battery terminals are tight as well as the ground by the oil filter. Scanmaster reads around 11.5-12.2 at idle and 12-13.3 under load whats wierd is a couple times Ive seen it fall to 6 something and go back up to the above mentioned volts. The other day my third brake light started working which hasnt worked since I bought the car 6mths ago then it wouldnt go off even with the ignition turned off, now its back to not working again at all.

I am running half 91pump gas and half 109 race gas as well as Razors Alcohol which haas a bad diafram in the pump at the moment so Im not sure if its spraying all the time but I figured I shouldnt be getting knock with the 109 added but Im getting knock as if im running on straight pump gas. Any suggestions? or advise?

 

[Black Car]

Take a reading with the engine running off the + post on the aternator.
Mine usually runs from 13.0 to 14 volts. Sounds like you may have electrical problems.

 

[salvageV6]

Does the VOLTS light light up in the bulb test key position?

 

[Robbie-87plz]

Had a low voltage problem a little while back, I went through the following-
.battery
.alternator-after replacing it, found it to still be low, replaced it a 2nd time
.new belt
-pulled the dash and cleaned the terminals on the low voltage light
-wiped down the plastic paper looking thingy
somehow it came together and she fires up ok now, runs good.
Good luck man.

 

[mybuick]

common problem with these cars now a days. the bulb connection gets corroded and that completes the charging ciurcut. using a pencil eracer cleans the contacts and fixes the problem unless it is a wiring problem. my friends car had this problem and mine does now.

 

[ANDYS87]

12.5V with car not running is normal..however when the car is running, your voltage should read from 13 to 14plus volts. You might want to buy and install the alternator field fix kit. I think Kirban sells it. It bypasses the battery warning light...it takes the weak link out of the charging system. Like others have said, the terminals could be corroded. Let us know when you fix the problem.

 

[ESP Products]

Good morning,
Regarding the low voltage. Don't place too much faith in the scanmaster. I have seen the Battery volts age is almost always low. Trust a voltmeter at the batter and back of alt. The terminals may be corroded as mentioned earlier, or you can go further and the wires themselves, may be corroded under the lining/coating. These are 18+ years old.

Hope this helps.

 

[TurboBob]

Good morning,
Regarding the low voltage. Don't place too much faith in the scanmaster. I have seen the Battery volts age is almost always low. Trust a voltmeter at the batter and back of alt. The terminals may be corroded as mentioned earlier, or you can go further and the wires themselves, may be corroded under the lining/coating. These are 18+ years old.

Hope this helps.

I disagree. The Scanmaster is not measuring the voltage, the ECM is. The ECM is very good at measuring things. The slow datarate just makes diagnosing fast changing data difficult.

However, corrosion is most likely the issue, but pulling the dash is a pain in the butt to chase a ghost. I hot wired my alternator by wiring a 470 ohm resistor fromt he fuel pump check connector to the L terminal on the alternator. It fixed all my problems, low voltage at WOT, and intermittant low voltage. Alternatively (pun intended) Caspers electronics has a plug-in doodad they call a "Field Fix" that does the same thing and is really easy to install......

Bob

 

[Robbie-87plz]

So a really darn good fix would be to gut the car before the next paint job and to rewire everything, providing I intend on keeping it? :biggrin: Instead of wishing for a "GT" series turbo/convertor...

 

[turbofrank]

I had same problem and solved it installing new pos/neg cables from Caspers.