70sgeek

Seems I have a power drain which renders the battery too weak to start the car after about 8-10 days of non-use. Car is parked inside my garage when not in use. Battery (Optima red) powers right back up when hooked to a full-blast charge and recovers fully on an overnight trickle charge.


Only full time powered accessory (other than the convertible top switch) is the repro rally tach/clock which I purchased new from Parts Place a little over 1 year ago. Works flawlessly but I wonder if that may be the source of my drain.


Anyone have similar issue traced back to a full-time clock unit (whether OEM or repro)?

VC455

Of those, only the clock draws power when the ignition is off. Because of the intermittent and short duration of the draw, the clock should take very little power.

Disconnect the power lead from the clock to determine if this is the problem.

70sgeek

that was my interim plan for the next sitting period if no other possibilities turned up. I agree though, clock should be drawing very little power, but I can't immediately think of anything else actually running full-time.


I haven't added any other full-time accessory items or butchered anything into the factory wiring.

Fun71

Try unplugging the square connector to the alternator. A shorted or leaky diode will cause a constant current drain.

oldcutlass

Do you have any aftermarket items, stereo components, alarm, etc...?

Dave26

I also noticed a power drain after installing the same tic toc tach....I am now always connected to my battery tender

joe_padavano

The tach operates off of switched power. If there is any power going to the tach with the key off, you either have it wired incorrectly or you have a problem elsewhere that is putting power on the switched power wires.

As noted, disconnect the power lead to the clock to see if it still causes a drain. The original spring powered clocks have a set of contacts that only turn on the motor when the spring needs to be wound up. If the contacts are fused, it can drain power. New quartz clocks are powered all the time and cannot draw enough to drain the battery unless there is an internal problem.

MichiDan

What Fun71 said. i spent quite a while tracing a key-off battery drain, and it ended up being an internal alternator problem.

droptopron

I had an inoperable repro tach when I first bought my car. Never bothered me so I left it in there. Then at one point months after I bought the car it started drawing like crazy. It will kill a fully charged battery in two days after the car sat. IDK what is up with those things but something isn't right.

70sgeek

So in update to the drain issue, had some time to diode test the alternator with my multimeter.


I have a 3-wire alternator (power post + 2-wire regulator plug on top of the casing)


testing from the power post to alternator case, that diode test appeared ok.


however, when I tested the 2-wire plug terminals I only garnered negligible readings, which according to my multimeter chart would be indicative of a short.


Assuming I properly tested the plug contacts (same post-to-case method each post), that could in fact be an issue.


While unplugged, I also performed a voltage test - initially the alternator power post registered 2-4 actual volts, momentarily dropping into the mv range within which it continued to fluctuate thereafter. The battery wire itself registered even volts with the battery - approx. 12.3v with all systems off.


Visually checked the firewall voltage regulator (a new Delco replacement from about 1 year ago) - all appeared intact as installed so I left it alone.


Have not pulled fuses yet but visual inspection shows all in ok shape - all fuses replaced about a year ago and the plug terminals are not corroded/rusty. Only full-time on accessory I have is the rally clock (not counting the stereo memory line).


The alternator was a brand-new Bosch piece purchased June 2016 or so - possible it's the culprit?

RandyS

You could unhook the wires to the Alt for a couple of days and see if you still have the drainage.

cherokeepeople

if this has the 6 separate diodes you need to disassemble the alternator to test all of em.

70sgeek

It's a Bosch AL530N (3-wire, 63 amp) which I purchased new (not reman) a little over a year ago. Battery is an Optima Red which I bought last year, doubt it's at issue.


Not sure how many internal diodes there may be


I going to sub in another alternator to see how that plays out, much preferable to taking my current one apart with no recourse anyway if bad after all.


appreciate all the feedback - still haven't isolated the problem definitively - will post further results as they may follow.

Fun71

I have replaced quite a few leaky diodes in my alternators over the years.