Barry W. Fox wrote: Bwfox@aol.com
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Fellow sworkers:
I have been fighting an electrical gremlin in my TR for the past
several days....
So a digital voltmeter across the battery after a thorough off-line
charge shows 12.6 volts at rest, falls down a coupla volts during the
start operation, then goes back to 12.6 or so. Putting the same DVM
from ground to the D terminal on the E reg. shows 14.5 (about what I
would expect). The charge current (according to my schematic) goes
from one of the A terminals through the ammeter thence to the batter
+ive term. This is where I need some help. Shouldn't the voltage
across the battery be in the 13.8-14.2 range just after starting? The
ammeter shows current flow but the voltmeter shows quiescent battery
voltage, and even I know you cannot charge a battery unless the E
applied is greater than 12V. Do these lovely Lucas ammeters have a
shunt just for this purpose and maybe mine is open circuited? As
usual, any and all info is appreciated.
Replies to foxb@macom.com will get read before those to AOL, FWIW.
Cheers,
Barry W. Fox 65 TR4A CT51681L
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Barry,
Sounds to me like the ammeter is bad. The battery is connected to
your D terminal via the ammeter and if the voltage is not the same
then either the ammeter is bad of there is one heck of a load on the
system (not likely since the voltage differential is 2.5 volts.)
Do this experiment:
1) disconnect the battery for safety reasons unless you want to
replace the wiring harness.
2) Disconnect the wires from the ammeter and connect both to one
terminal (either terminal.)
3) Reconnect the battery.
4) Retest the system and see if the voltages are now the same.
If they are then you need a new ammeter. I haven't seen a bad
ammeter but it could happen if there was a short circuit at one
time or another. You can operate the vehicle with the ammeter
hooked up this way indefinitely but you would not have an ammeter
(as so many cars on the road have.)
Good luck
Dave Massey St. Louis, MO USA
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