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1939 La Salle Something draining battery

Started by 39LaSalleCaddad, October 10, 2017, 05:44:31 PM

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39LaSalleCaddad

Hey folks.

New battery, rebuilt starter, generator and cleaned up connections in charging/starting circuit.

Meter shows that the system is charging.  However, turning the car off and sitting over night something is draining the battery.  No visible lights are on.  Friend recommended recharging the battery then removing one fuse at-a-time and seeing if the battery stops sparking when I connect it.  Then see what is connected to that fuse in the wiring diagram.  It currently sparks considerably when I connect the battery.  I learned it is positive ground and am connecting it correctly.

Just wanted to run this by you guys and see if this is a good way of finding out what is draining my battery.

Thanks!

The Tassie Devil(le)

The fact that the terminal sparks when connecting it to the battery, there is definitely a current draw.

Removing fuses is a good idea, but check things like a light being left on.   Not sure if these cars have a trunk light, as these can create a drain.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

39LaSalleCaddad


bcroe

My recommendation is after shutting down, disconnect a battery post and
connect a small light bulb between the disconnected points.  It will show
any significant drain; you can start disconnecting fuses, etc until it goes out.

Bruce Roe

Paul Phillips

I don't have the exact wiring diagram in front of me, but in general, there is a primary feed to the starter solenoid, with a tap from there that goes to the ammeter.  Other side of the ammeter goes to the voltage regulator, ignition switch & cigar lighter/body lightning, and a feed to the light switch with its integral circuit breaker. If you have a draw with the ignition off, then the problem is more likely to be within one of these branches. This is a stepwise search, as below.

If you can, connect an aux ammeter (VOM type) in the battery primary circuit and see how much current is flowing. Then carefully disconnect the lead to the car's ammeter - if the current flow remains on the aux/test ammeter, the leak is in the solenoid or associated wiring. If there is no current, the leak is in the rest of the circuit. If the latter, restore the wiring on the car ammeter, then disconnect the Bat terminal on the voltage regulator.  If current flow goes away, the problem is in the regulator or generator, if not, you need to look further. Restore the connection on the regulator and disconnect the primary feed to the light switch, probably at the back of the switch with a red tracer. If the current leak goes away, problem is in the light switch or associated, wiring, if no, it is in the ignition/cigar lighter/body feed circuit. Follow the same process to disconnect and isolate each of these branches. When you disconnect the offending circuit, current flow on the aux ammeter will.go away.

Good luck!

Paul

Paul Phillips CLC#27214
1941 60 Special (6019S)
1949 60 Special (6069X)
1937 Packard Super 8 Convertible Victoria
1910 Oakland Model 24 Runabout

39LaSalleCaddad

Paul,

That is phenomenal troubleshooting advice. Can't wait to execute and report back!

Javier

Steve Passmore

If your 39 is wired as it came from the factory it would have no fuse box,  If it's been re-wired since and has a fuse box the problem could be anywhere in the altered wiring or a fault with exactly how it was wired. Someone may have wired a system bypassing the ignition switch??
Steve

Present
1937 60 convertible coupe
1941 62 convertible coupe
1941 62 coupe

Previous
1936 70 Sport coupe
1937 85 series V12 sedan
1938 60 coupe
1938 50 coupe
1939 60S
1940 62 coupe
1941 62 convertible coupe x2
1941 61 coupe
1941 61 sedan x2
1941 62 sedan x2
1947 62 sedan
1959 62 coupe

39LaSalleCaddad

No fuse box. Original wiring. Back to the drawing board I guess.

Bob Schuman

If the car has its original clock that is connected, and has not been converted to a modern quartz movement, that is a likely source of your current draw. The clock was factory wired to run all of the time, It should not drain the battery overnight, but the clock may have a problem.
Bob Schuman
Bob Schuman, CLC#254
2017 CT6-unsatisfactory (repurchased by GM)
2023 XT5

Steve Passmore

Good point from Bob, that's the only thing powered all the time, but I would think you would smell a short if the battery drained through it overnight.    The original wiring itself could be the fault. The insulation will definitely be extremely brittle and could be failing somewhere where you can't see it.
You will have to carry out the tests as Paul described and hope if its a fault in the wiring that will be visible.  Usually, only the starter could stand that amount of power drain without melting wires. Even rebuilt ones have been known to be bad? 
Steve

Present
1937 60 convertible coupe
1941 62 convertible coupe
1941 62 coupe

Previous
1936 70 Sport coupe
1937 85 series V12 sedan
1938 60 coupe
1938 50 coupe
1939 60S
1940 62 coupe
1941 62 convertible coupe x2
1941 61 coupe
1941 61 sedan x2
1941 62 sedan x2
1947 62 sedan
1959 62 coupe