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Dash Volt Guage Readings

glen3107

Active member
Joined
Jun 17, 2002
Messages
26
Location
Atascocita, Texas
Corvette
1987 Black Coupe
Went out to start my car two weeks ago and found the battery was dead. I put it on the charger and it would not take a charge, so... I went to my friendly Sears store and got a new battery (no charge, under warranty).

This week, while stopped at a light, the car died. When it started, the dash volt guage read 11.7. The next morning the car would not start at all. I recharged the battery and took it to an O'Reily's and had the altenator checked. They tested the battery and the alternator with a multimeter. The battery showed as OK, and the alternator showed low charging.

I took out the altenator and asked them to test it again. On the instore test machine, it showed that it was charging at 10 volts.

I bought a new one. I asked them to test the new alternator on the same machine before I left the store. It showed that it charged at 14 volts.

I went home and put the new alternator in the car. I went back to O'Reily's and asked them to check the new alternator on the car. On their multimeter,the battery showed good, and again the new alternator was low charging(?).

The battery cables are clean and tight and all the connectors on the alternator are tight. The drive belt is taunt.

When I drive the car with the new alternator installed, the dash volt guage shows 13.8 when driving and 12.2-12.3 when idling. Could you'all tell me if this reading is a normal voltage range or do I need to look further.
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
12.3 is LOW

Unless your@ idle, A/C on & headlights
.. @ 2krpm you should be in the mid 13 zone.

When the car 1st starts.... you should be in the LOW 14's...

I would continue to investigate....


Vig!
 

glen3107

Active member
Joined
Jun 17, 2002
Messages
26
Location
Atascocita, Texas
Corvette
1987 Black Coupe
Thanks Vigman for your advice. Seems like my car is more electrically challenged/challenging than I thought it would be when I bought it. I'll keep on looking.
Thanks again.
John
 
Joined
Aug 30, 2002
Messages
1,533
Location
Colorado Springs, CO USA
Corvette
84 Z51 auto R.I.P. 89 black roadster SOLD
When you took it back and had the new alternator tested in the car, what was the voltage reading their meter showed, and did this match your voltage gauge?

It is possible that you may have something that's putting too much of a load on the alternator. The alternator is designed to output a [theoretically] fixed voltage (14 or so) while delivering a varying amount of current, depending on the load placed on it (lights, heater/AC motor...etc). If something is trying to draw more current than the alternator is designed to deliver then the voltage output of the alternator will start to drop off.

Good luck!

Bill
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
OR.......

Fusible link "C" is dying or dead this is the OUTPUT link off the Alt... ( saved MY bacon from those STUPID PEP BOY'S ALT)

under the hood there is a gaggle of red wires behind the battery... this is a power distribution stud.. and MOST of the main feeds wind up there.


Now IF the ALT is good but the line is HI Z .. no juice will get to the batt ( or any other systems) and the Alt will self destruct without being to drive a load.. so measure the back STUD of the Alt..if it's the same as the batt voltage the wires fine.. and your problem is elsewhere!

Vig!
 

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