Hello,

I apologize, I am uncertain as to whether or not I am posting to the correct forum. I could not find a specific RSX forum so this seemed like the most logical place to make this post.

I have a neighbor who was hitting me up for jump starts almost on a daily basis. Now I have some education in electronics from way back and have refreshed my knowledge in recent years playing with Arduino's etc. so last week I grabbed my Fluke meter and went to his place and said, "let's find out why your battery is draining" ... he said his battery is less than a year old and that this problem didn't start until recently (a few weeks ago) ... he told me that if he starts his car at 10pm and lets it run for a half an hour, that he will be able to start it in the morning and go to work ... but if he did that routine at 7pm then come 6am it would not start.

Anyways ... I checked the alternator at engine idle and while under load (all doors open, AC unit turned on, radio on, brake pedal pressed down ... putting as much of a load on it that we could think of) and the alternator kicked out a solid 14.8 volts without a hiccup.

So I asked him to turn the car off, and I disconnected the negative terminal from the battery and put my meter in series with the car to see if it was pulling any current while everything was turned off, doors closed etc. and sure enough, it was pulling around 375ma. which would sometimes jump to around 400 briefly from time to time ... well, I realized that over time, this would definitely deplete his battery and cause the symptoms he was describing, especially since his drive to work is only about 10 minutes in one direction ... not enough time to charge a battery from a dead state when its got a drain on it especially ... I didn't really know what to do next other than try to isolate which circuit was causing the drain, so I figured pulling fuses made the most sense and that's what I did until I found the culprit ...

A 7.5 Amp fuse labeled simply as BACK UP in the engine compartment fuse box. When I pulled that fuse, the current drain went down to 15ma ... certainly acceptable to me ... but when the fuse was re-inserted, it went back up to 375ma.

I should point out that I made sure that the car was off and the doors closed for at least 20 minutes before I started troubleshooting the problem because I know that ECUs can have a tendency to stay on for a while after a car is turned off. And with the time it took to go through the fuses under the dash then under the hood, it was at least 45 minutes into this process where the battery was absolutely still draining off at that current rate.

Also, since we found the issue, he now just pulls that fuse when he parks and does nothing else and his battery does not drain overnight as it use to (we did this troubleshooting on December 30 so it has been enough days now to see the benefit in removing the fuse as normally he would be needing a jump start by now).

I found a shop manual online, and discovered that there are MANY different circuits that are in line with that fuse (actually, I was rather impressed with this car after going through the shop manual ... it is fairly complex for being 20 years old) ... so I'm at a point where I'm not exactly sure how to continue troubleshooting this problem.

I did find some forum posts via Google that reference that specific fuse and this specific problem with this specific car, but none of those posts discuss any sort of solution to the problem nor any legit troubleshooting steps beyond replacing the head unit ... which never worked for any of them.

Has anyone out there ever dealt with this specific parasitic drain before? Or can anyone offer any wisdom in isolating and fixing the cause of this drain?

Thank you,

Mike Sims

 

Look at all the loads that the circuit powers and disconnect one load at a time.

By the way, 14.8V is a bit high for a standard FLA battery (or does he have an AGM battery) and charge voltage is temperature dependent. Now if it was ultra-cold, maybe.

 

I thought it was a bit high as well, but it didn't seem alarming to me being well within the 10% rule of thumb. And it is a bit cold up here ... we live in the high desert in southern California ... "cold" is relative, I get that, but it typically gets down into the low 30's(F) at night.

 

I cant edit my posts yet and forgot to answer your other question. His battery is just a standard maintenance free low end type that you can get at any Auto Zone ... it didn't stand out to me as anything special. Not like the Optima I have in my Z ... his was just a run of the mill black label battery. It kind of struck me as being a bit smaller than what one might expect to see in a car that size, but what do I know ... technology changes all the time and for all I know it could be a power house packed in a smaller package.

 

Mynocks. Sounds like Mynocks.

 

Mods: Sounds like a candidate for the Integra forum.

 

Nothing wrong with those. Both factory installed Panasonic FLA batteries lasted 14 and 16 years in my vehicles. I have yet to have a "high-tech" AGM battery last longer.

This is a charge and float voltage for an AGM battery. Source: East Penn battery. A standard FLA battery would about 0.2V less.

 

"BACKUP" appears to be fuse #9 in the underhood fusebox.

I found the electrical schematics for your RSX

https://portal-diagnostov.com/en/roo...ring-diagrams/

Here are the power distribution schematics so I'm trying to determine what is powered by fuse #9 underhood, unfortunately they want money for the remaining schematics

https://portal-diagnostov.com/en/202...ring-diagrams/

But another RSX has had the same problem as your RSX with Backup draining the battery
https://www.clubrsx.com/threads/backup-fuse.804548/

Check to see if you have any accessories plugged into the cigarette lighter (IE USB power plug)

 

Short in radio. Remove the radio and unplug it, see if the drain stops. This was a common issue when I was an ASE master certified Technician for Acura.

 

Any luck finding the problem.