Electrical Draining

[Greg2013SHO]

I use my 1989 SHO rarely. It’s more of a hobby than a daily vehicle. Often I find that battery is dead when I try to start it again. I understand months of no use but not weeks. This last time I was gone for over 2 months so gave it a trickle charge, to a new model Premium Die Hard. I know that brand is over-hyped but it was the best available at my local parts store. The charge went on for 8 hours. I pulled the plug for the overnight; didn’t want to risk an accident while I slept. The next day re-charge showed more amperage than at the end of the previous day. I took that to indicate some significant drainage overnight. No wonder the battery goes dead so soon! Is there something about this model that uses more-than-expected electricity when the car is off? The accessories seem to be standard. Thanks.

 

[luigisho]

not normally. At this age I have the same issue. probably have a short somewhere but I haven't had time to dig into it. I bought something like this for a temporary band aid.

Amazon.com

It at least slows the battery from draining too quickly. Always have a set of jumper cables just in case though. To actually fix it you probably need to probe for shorts. I have seen some decent videos on youtube that are helpful for that

 

[luigisho]

I think they carry them at autozone for cheap. Works ok. Haven't drivent the car in a while..

 

[Greg2013SHO]

Thanks - worth the look.

 

[GEN 3 SHO FAN]

For the Gen 3, according to some posts about power drain pointed at the tape player IIRC...

 

[Greg2013SHO]

For the Gen 3, according to some posts about power drain pointed at the tape player IIRC...

thanks for the tip - I don't think that's it in this case but other vehicles have had it - I'll be having the car diagnosed by a shop; will report the results

 

[Irish Pride]

Double check the visor lights. Make sure they are turning off. My drivers visor had a broken cover over the mirror so I removed it. Somehow the light was coming on when I had the visor in the up position. I couldn't see the light so I never knew. With some diligent searching I finally zeroed in on it. I disconnected the light and my drain went away.

-Chad

 

[BaySHO Performance]

Another possible drain is the hood light. Do you have a car alarm? Those are notorious as well.

One of my cars is rarely used, so to stop the battery draining, I installed one of these on the negative terminal:

https://www.oreillyauto.com/detail/c/super-start/super-start-terminal/ss00/ss31186/v/a/5542/automotive-car-1989-ford-taurus?q=SS31186&pos=0

 

[FastCAD]

To much junk in the glove box will trip the light on. 12v all night will run down the charge pretty quick.
Bin der dun dat.

 

[Ta2dResqr]

Just saw a video about tracking down a draw. Guy used a thermal camera to see which relay/fuse was the hottest which lead him to the circuit and helped narrow it down. Had never thought of that before but it worked awesome.

 

[BaySHO Performance]

That's awesome! Don't see why an infrared thermometer won't work as well. I'll have to try mine next time.

 

[PaulTAutoX]

I use my 1989 SHO rarely. It’s more of a hobby than a daily vehicle. Often I find that battery is dead when I try to start it again. I understand months of no use but not weeks. This last time I was gone for over 2 months so gave it a trickle charge, to a new model Premium Die Hard. I know that brand is over-hyped but it was the best available at my local parts store. The charge went on for 8 hours. I pulled the plug for the overnight; didn’t want to risk an accident while I slept. The next day re-charge showed more amperage than at the end of the previous day. I took that to indicate some significant drainage overnight. No wonder the battery goes dead so soon! Is there something about this model that uses more-than-expected electricity when the car is off? The accessories seem to be standard. Thanks.

All great responses. I think mine is draining from a bad ignition switch - it wasn't reliably going to full off. Worn switch, you could sometimes remove the key without turning it off, etc. Got a replacement to put in before I change the battery again, it killed the last one past recharge-ability.

 

[Greg2013SHO]

Thanks to all. I just got back from a long trip so have been putting my stuff in order. One of them was my laptop to the Mac shop. My ears are back on so I can consider all these tips. Much appreciated.

 

[luigisho]

Good tips all through this thread.

 

[PaulTAutoX]

OK, got the new ignition switch in, and a new battery. Car runs, yay!

Electrical still has a significant drain, appears to be ~0.8A. I checked the various lights -
no underhood light,
no trunk light,
visor light for driver goes off properly, visor light for passenger doesn't seem to work at all.
Turned stereo on and off, the amp is crapped out but it makes crackles through the speakers and there's a load that goes on and off with the power switch.
Glove box light goes out when closed, confirmed.

Any other candidates? .8A is way too much for the stereo's memory maintenance circuit I think. Likewise for the clock.

I guess I can try the thermal camera idea, I have a little toy one, but unsure if .8A will be enough to really heat things up. Likewise with optical thermometer. If that fails it's down to find long enough test leads (battery is in a trunk box) to bring the meter into the passenger compartment, then pull fuses one by one I guess.

 

[Ta2dResqr]

If you leave the car for a few hours, everything should be ambient except the circuits drawing. That may help with the heat seeking method. As far as having to have the meter in the car, either a friend to watch the meter (Stand here and drink this beer, tell me if the meter changes) or walking back and forth from the fuse box to battery (get your steps in) will solve the long test lead issue.

 

[BaySHO Performance]

Parasitic battery draw should be no more than 50 mA.

 

[PaulTAutoX]

OK, inviting all geniuses to peruse my results here.
While I didn't quite follow Ta2dResqr's advice (nobody handy to bribe with a beer, and the point was not avoiding steps but to not have to get up off of the kneeling pad too many times).... I folded out the fuse block and first tried using the infrared gun to read things. While the upper half fuses were maybe 1-2 degrees F warmer, that's nothing I would make a decision on.

So I set up the meter so I could read it through the rear window, stuck a flashlight on it (dusk was approaching) and pulled fuses one at a time watching the current load, replacing them after each measurement.
W. T. H.? I have four fuses that show noticeable current drop when I pull them individually! Taking my own advice (long story) I attach a pic of the block and have noted the drop in current for each of them on the pic. One was low enough to count as Nick's parasitic current, the others are more vampiric: 40, 150, 270, and 300 mA. And the total drain actually varied from maybe 670 up to 730+ over the time I was in there. Maybe because I was freshening up the contacts?

The only good news is that the cute little fuse puller tweezer in the back of the fuse box cover still works thirty years down the road, if you wiggle the fuse a bit.
#6 is a 15A, 8 - 15A, 11 - 20A, and 17 - 15A were the suspects. I took the pic while #8 was out.

Couldn't find my actual Ford shop manual in a quick search, it's around here somewhere, and the Chilton's is just barely better than nothing concerning wiring, so I am not sure which systems are fed by these.
I shrunk the picture down so it fits on the average screen. I wait with bated breath for words of wisdom - I'd really rather not have to put in one of those battery cable cutoffs....

 

[FastCAD]

OK, inviting all geniuses to peruse my results here.
While I didn't quite follow Ta2dResqr's advice (nobody handy to bribe with a beer, and the point was not avoiding steps but to not have to get up off of the kneeling pad too many times).... I folded out the fuse block and first tried using the infrared gun to read things. While the upper half fuses were maybe 1-2 degrees F warmer, that's nothing I would make a decision on.

So I set up the meter so I could read it through the rear window, stuck a flashlight on it (dusk was approaching) and pulled fuses one at a time watching the current load, replacing them after each measurement.
W. T. H.? I have four fuses that show noticeable current drop when I pull them individually! Taking my own advice (long story) I attach a pic of the block and have noted the drop in current for each of them on the pic. One was low enough to count as Nick's parasitic current, the others are more vampiric: 40, 150, 270, and 300 mA. And the total drain actually varied from maybe 670 up to 730+ over the time I was in there. Maybe because I was freshening up the contacts?

The only good news is that the cute little fuse puller tweezer in the back of the fuse box cover still works thirty years down the road, if you wiggle the fuse a bit.
#6 is a 15A, 8 - 15A, 11 - 20A, and 17 - 15A were the suspects. I took the pic while #8 was out.

Couldn't find my actual Ford shop manual in a quick search, it's around here somewhere, and the Chilton's is just barely better than nothing concerning wiring, so I am not sure which systems are fed by these.
I shrunk the picture down so it fits on the average screen. I wait with bated breath for words of wisdom - I'd really rather not have to put in one of those battery cable cutoffs....

 

[BaySHO Performance]

Was that fuse panel diagram for a '92 (which is what Paul has)? The layout differs from year to year.