Dead Roadmaster Battery <1 year old

Wiring, DIY, lighting, etc.
Fast_Ed
Posts: 550
Joined: Wed Oct 23, 2013 9:45 pm

Dead Roadmaster Battery <1 year old

Post by Fast_Ed »

Roadmaster interior lights didn't come on this morning when I went to get in. No surprise that it wouldn't even try to crank either. Tested the battery at 5 volts.

Battery is a Napa legend bought less than a year ago in prep for the ski trip.

Borrowed Kevin's clamp meter but couldn't get it into any of the crevices that all of my battery cables run through. Tested several separately and saw no major draw.

The 10A feed on my Fluke is failed; turns out I already blew that fuse. Will pick up several tomorrow but meanwhile used the mV setting to test the voltage drop of the underhood fuses. One time saver here is that this panel feeds the interior one. No draw here means no draw there.

Tested all of the underhood fuses.
0 mV with interior lights off
0 mV with interior lights off
All measured 0 mV. Opened the door to turn on an interior light and measured 1.1 mV on the 60A Body 2 fuse.
1.1 mV with interior lights on
1.1 mV with interior lights on
https://www.powerprobe.com/fuse-voltage-drop-charts
This handy website Kevin found indicates that 1.1 mV voltage drop over a 60A maxi fuse means there is a 1236 mA load. I suppose 1.2A is reasonable for all the interior lights, so physics apparently does apply here.

Plan for tomorrow is to pick up a new battery along with several new fuses for the Fluke. I will then put my meter into harm's way and test the amperage between the negative cable and terminal.

If less than 50 mV, then I will conclude that it was a bad battery and move on.
Fast_Ed
Posts: 550
Joined: Wed Oct 23, 2013 9:45 pm

Re: Dead Roadmaster Battery <1 year old

Post by Fast_Ed »

Update:
Battery had charged to approx 12.1 as of about 930pm last night. This morning around 0630 it is down to 11.78.

Not a huge discharge over 9 hours.. but it's nonzero and the battery was not connected to anything. Had it dropped several full volts I would be a lot more comfortable concluding this is a faulty battery issue only.
Fast_Ed
Posts: 550
Joined: Wed Oct 23, 2013 9:45 pm

Re: Dead Roadmaster Battery <1 year old

Post by Fast_Ed »

Put new battery in and got a cheapo meter from HF to sacrifice in line with the negative feed. It has an unfused 20A input.

When put in line with everything off, it registered less than 1 mA. Appears that the Roadmaster uses very little power when off.

Started her up. Charging at 15.00v. took her around the block and I'm at 12.53 V
Cheap meter has hold feature
Cheap meter has hold feature
Will test again tomorrow morning before I leave. No smoking gun here to fix... Locks still work, so if that's what stuck, at least it didn't cause damage. I guess I just keep driving it and hope for the best.
Fast_Ed
Posts: 550
Joined: Wed Oct 23, 2013 9:45 pm

Re: Dead Roadmaster Battery <1 year old

Post by Fast_Ed »

IMG_20200131_071754605~2.jpg
And the result this morning.. dropped from 12.53 to 12.08 overnight. Would have preferred no voltage drop.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Dead Roadmaster Battery <1 year old

Post by kevm14 »

Fast_Ed wrote: Thu Jan 30, 2020 7:01 am Update:
Battery had charged to approx 12.1 as of about 930pm last night. This morning around 0630 it is down to 11.78.

Not a huge discharge over 9 hours.. but it's nonzero and the battery was not connected to anything. Had it dropped several full volts I would be a lot more comfortable concluding this is a faulty battery issue only.
I don't think you had a faulty battery before, or at least the evidence doesn't fully support that. Did you get a free one though?
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Dead Roadmaster Battery <1 year old

Post by kevm14 »

Fast_Ed wrote: Fri Jan 31, 2020 8:39 am IMG_20200131_071754605~2.jpg

And the result this morning.. dropped from 12.53 to 12.08 overnight. Would have preferred no voltage drop.
That's not right. However, what you really should do is fully charge w/ Battery Tender (or similar smart/auto charger) and see what that does while sitting. Some portion of that may have been a surface charge.

Check the date on the new battery. It didn't have a full charge and needs to be charged before you can really assess what's going on.

To be clear, a 0.5V drop overnight on a fully charged battery is obviously a sign of an issue, most likely a parasitic draw given the brand new battery. In nominal temps, something around 12.8V constitutes a fully charged lead acid battery, and that's after sitting, not directly after removing the charger (or shutting the car off).
Fast_Ed
Posts: 550
Joined: Wed Oct 23, 2013 9:45 pm

Re: Dead Roadmaster Battery <1 year old

Post by Fast_Ed »

When I left for Quonset, the battery voltage had dropped to 11.7. yeah, something isn't right.

I delved into the inner fuse panel and checked the draw on all of them. Found draw on two fuses.

#41 FWD LPS had a voltage drop of 5.6 mV which went to 0 if I held down the door switch until the interior lights went off.

#35 CTS/PWR LK has a drop of 10.8 mV. I tried disconnecting the power lock switches, no change. Tried disconnecting the horribly located and now bloody lock relay, no change.
Fast_Ed
Posts: 550
Joined: Wed Oct 23, 2013 9:45 pm

Re: Dead Roadmaster Battery <1 year old

Post by Fast_Ed »

Haynes manual circuit diagram
Haynes manual circuit diagram
Anybody have the FSM for a 96 Roadmaster? This can't be everything on this circuit. I re-verified that my car doesn't have keyless by checking the location above the drivers rear wheel well
Fast_Ed
Posts: 550
Joined: Wed Oct 23, 2013 9:45 pm

Re: Dead Roadmaster Battery <1 year old

Post by Fast_Ed »

I would "happily" delete my power locks at this point, but when I remove that fuse the car buzzes at me. I'm sure that buzzing uses some battery as well...
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Dead Roadmaster Battery <1 year old

Post by kevm14 »

I will get you what I can from my electronic FSM hopefully later this evening.
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