Acceptable level of Power Drain

[just_ridin]

So the next question as we're troubleshooting the beast of a '71 Super Cheyenne is...

Is there a natural dropoff in the battery power when it sits? I'm guessing there shouldn't be much at all, as you should be able to start your vehicle effortlessly if it sits for a month...

We're losing power ever-so-slightly...the battery was reading 12.05 at 8pm, and at 6am it was 12.00. We did some searching and found a crushed cargo light bulb (light broken and socket crushed...seriously..how does that happen without damaging the housing?). Prior to remedying that we were losing about .01 every 20 minutes, then less than .01 per hour after that.

Any thoughts on what could be draining power at that low of a level? She used to hold power just fine, but then replaced the dash (same gauges, but had to replace the printed circuit), took out the voltage regulator for an alternator/regulator combo, replaced the fuel tank sending unit, cut the radio wires, and repaired the aforementioned cargo light.

As always, help/thought/input/advice is greatly appreciated.

[Stocker]

Pretty sure there are already threads about chasing electrical draw.... I would start with a VOM (or a simple test light) and pull fuses one by one looking for a current draw.

[davepl]

I'd hook your meter up in ammeter mode, see what the draw is. If you're drawing an amp, for example, you have 1 amp hour per hour, or 24 amp hours per day. See what your battery reserve capacity is to figure out how long it'd hold that charge.

If it's too much, start pulling fuses to see if you can isolate the source of the drain.

It's about a 95% chance that it's aftermarket electronics of some kind. There's just not much in these trucks from the factory that could do it.

[Shinysideup]

First of all 12.05 is not a charged battery. It needs to read better than 12.5
How old is it anyway?

[just_ridin]

Originally Posted by Shinysideup

First of all 12.05 is not a charged battery. It needs to read better than 12.5
How old is it anyway?

The battery is pretty darn new, but troubleshooting a few other items left us with a charge of 12.05 at the end of the day...left it off the tender overnight to see what the draw would be over a 10 hour span.

[LongBox]

I assume the units of measure you put in the OP was volts. A fully-charged lead acid battery would be around 12.6 volts. As someone already pointed out, there's not much to drain power in these vehicles unless someone has added aftermarket electronics. The cargo light would only affect the battery if it was switched on, and the crushed bulb had a short, but it should blow the fuse first.

Just for reference, I had a car that would drain the battery overnight. It turned out to be the trunk light staying on. It took a good 8 to 12 hours before the battery was at the point where it would not turn the engine.

While it is worthwhile to isolate the area of drainage (if there is one)k by pulling fuses and putting an ammeter in place, I'd first of all just put an ammeter in series with the negative battery terminal when the truck is parked. Should be no reading at all. If there is no reading, perhaps the real problem is the charging circuit.

[just_ridin]

Originally Posted by LongBox

As someone already pointed out, there's not much to drain power in these vehicles unless someone has added aftermarket electronics.

That's the puzzling part....there's no stereo in it at all. The only thing aftermarket other than the confiscated NASCAR intake and headers/flowmaster exhaust is the Clerks II DVD we found in the glove box when we bought it. There were some vintage 1974 speakers mounted on the cab pillars, but those were taken out and the ends capped. There's just the stock AM radio in there, and it's not even hooked up.

[just_ridin]

Appreciate the help once again guys...interesting/frustrating night of chasing a short.

While the reverse ground test showed the short coming through the back end/tail light fuse, we disconnected everything and chased the wires all the way back to the fuse box without finding a single thing wrong.

Some fidgeting in there led us to the short being in the interior light circuit somewhere (bulb's in and we have a short). Without knowing exactly where it is and having no desire to begin that search at 9pm, we just put the bulb in the glove box and ran off for a frosted barley pop or two.

For when we get back to it, it seems to me there's a lot of room for shorting there...fuse-to-light switch, light switch to door switch, door switch to light housing, and the housing itself...have to search and see if any of these problems more frequent than others I guess...again, thanks for the input. Still becoming acquainted with these beauties, and need to learn as much as possible (have two more ready to build after this one!).

Best,

J_R

[James the III]

Disconnect the alt, and see if the drain stops, if not, disconnect the regulator also..
if not reconnect..
then disconnect the starter selnoid . yes or no..
My bet is a faulty starter stator

[67 chevelle]

Originally Posted by just_ridin

Appreciate the help once again guys...interesting/frustrating night of chasing a short.

While the reverse ground test showed the short coming through the back end/tail light fuse, we disconnected everything and chased the wires all the way back to the fuse box without finding a single thing wrong.

Some fidgeting in there led us to the short being in the interior light circuit somewhere (bulb's in and we have a short). Without knowing exactly where it is and having no desire to begin that search at 9pm, we just put the bulb in the glove box and ran off for a frosted barley pop or two.

For when we get back to it, it seems to me there's a lot of room for shorting there...fuse-to-light switch, light switch to door switch, door switch to light housing, and the housing itself...have to search and see if any of these problems more frequent than others I guess...again, thanks for the input. Still becoming acquainted with these beauties, and need to learn as much as possible (have two more ready to build after this one!).

Best,

J_R

Check door switches first they are notorious for "issues"