Battery Draining Need Help!
 

Ok so, bear with me. Recently my car has been draining the battery after setting for only a couple days. It’s been about 3 years since the last battery so I thought I might have been the battery, I replaced it and it’s still doing the same thing. Before I got it, that fans have been wired to run when the ignition is on, and an aftermarket radio was put in. Since I’ve gotten it, I put in after market combo lights, replaced the fans with rx8 fans (1 was locked up) and that’s all electrically speaking. I would like to trouble shoot it and figure out what’s causing it but I have no idea where to start....idk if they have common wiring issues, or just a place to start in general, thanks for any help!

First, make sure that the radio and interior lights (dome, glove box, rear hatch) are all off when you remove the key and exit the car.

9 times out of 10, it's aftermarket electronics. Bone stock cars don't usually have problems. I have seen messed up pop up headlights that get stuck and the motor is still running trying to move the headlight, that's about it on a stock car. Most likely something aftermarket is a problem or something dumb like Resterof said, a light that is staying on or something.

Humble Mechanic has a good how-to on finding parasitic draws -


Dale

Great info, thanks guys! I’ll start there and see if I can find anything

My nearly bone stock FD with > 7 year old battery will start without issue after 3-4 week hibernation.

This was a fun video to watch to demonstrate how much aftermarket wiring could be removed

Wow mine will set for about a week and be dead. I checked to see if there was any draw on the battery and it measured 0.15 amp, can anyone confirm if this is normal? Or should it be 0.00? On the videos they were saying a 2-4 amp draw would kill your battery

I've never measured the dark current on my '94, but during the winter it sits for extended periods in a garage that has no electrical service, so no trickle charger. The battery (Optima Red Top) slowly discharges but will still start the car after a few weeks. I found that the battery lasts longer if the factory alarm system is not activated.

The '94 factory service manual at page G3 says that dark current should be 20 mA (0.02 Amps) or less.

thanks for the info! That’s what I was wondering. So at 0.15 dark current, it should be fine. I’ve also done some reading saying that is the alternator is bad and can discharge the battery? With the dark current being within spec, that’s the only other thing I can think of, unless I’m overlooking something

What units are you measuring? Are you seeing 0.15 amps or milleamps?

1 amp = 1,000 milliamps, so if you are seeing 0.15 amps, that converts to 150 milleamps, which is way more current draw than the 20 milleamps spec.

good point, I’m measuring on the 10amp setting on the multimeter, so you’re right it would be 150 milliamperes, I was off by a decimal, thanks for catching that. So in reality based on my setting it should read 0.02 or less correct?

Yes, with the meter set to measure at that 10 amp range, the car should be drawing at or below 0.02 amps. However, when a meter is set at the 10 amp range, 0.02 amps is probably too small a value to measure very precisely. Instead, can you set the meter to a lower range, say 1 amp, or better yet, does it have a milleamp (mA) range?

On the other hand, if you now are seeing a dark current of 0.15 amps with the meter set at the 10 amp range, the meter is precise enough to tell you what you need to know -- that the car's dark current is excessive. Something is drawing too much power from the battery. As Dale said, it is probably aftermarket electronics, or the dome light or rear hatch cargo light.

It’s just a harbor freight multi meter, nothing too fancy, i believe it only has a 10amp setting. I will definitely check those area for parasitic draw when I get home from work though, I appreciate the input!

50 mA is generally considered parasitic. Keep unplugging fuses until you find your culprit. Leaving the key in will draw more amperage ei: Leaving key in all winter is sure to kill the battery... at least in my car.
I did end up measuring draw on my FC with and without key at some point. It was a measurable difference but I can't remember the exact numbers.

There's a lot of good advice in this thread, once you know how to measure current you simply pull each fuse one-by-one until you find which fuse (or fuses) make the drain stop. Even if you don't understand what gets powered by that fuse, keep good notes and others here might be willing to help walk you through the wiring diagrams.

I once helped someone check for drains 10-15 years ago and the little orange light near the ignition key threw us off the trail because it was drawing current when the doors were open. Try closing the doors while testing.

Yea definitely a lot of good information, and I really appreciate it from everyone. I had to prioritize work and yard work the last few days so I haven’t gotten a chance to mess with it, but I’m going to tonight and hopefully I can find something

Once you've pulled fuses and identified the circuit that has the draw, you can also check relays on that circuit as they can fail or rust up causing a draw.

I had a short on the room fuse circuit and a battery drain problem ever since i owned the car. Turned out the audio relay in the front relay box was corroded inside and was the source to all my problems.

oh good call, I didn’t even think of that! I found my culprit though it’s the 10amp fuse under the kick panel

https://cimg7.ibsrv.net/gimg/www.rx7...da1923baf.jpeg

Also when I was undoing the door sensor (just taking the ground screw out) I heard an actuator type sound, it sounded like it came from between the antenna and door, and my multimeter temporarily went down to 0.00, I have no idea what that was about.

That's progress. You have a few things to check:


https://cimg8.ibsrv.net/gimg/www.rx7...53ba3b5d2b.png

That’s perfect thanks! What’s the pcmt and pcme?

I think it's engine ECU and auto trans ECU at a guess. Typically PCM = Powertrain Control Module.

Dale

SAE standard abbreviations:

PCME = power control module (engine) [formerly ECU]
PCMT = power control module (transmission) [formerly EC-AT control unit]

that makes sense thank you! So to test and see what’s causing the drain, I would just “unplug” the corresponding piece? Like take the radio out, test for a draw, remove cluster, test for a draw, ect?

Cluster? Have you already tested and eliminated all the easier things -- glove box light, dome/door lights, rear hatch light, and then the power antenna and your aftermarket radio? (if your car is pre-'94, there was a Mazda bulletin about faulty glove box light switches that wouldn't turn off.)

oh no I haven’t, I was just giving examples, it’s a 92, I just took the aftermarket radio out and it didn’t make a difference, the rear hatch light doesn’t turn on, to rules out causes I just remove the bulb right?

also found out I had a stripped antenna wire being held into the antenna port with a drywall screw, that was new to me lol

and idk if I’m just dumb and not seeing it, but I don’t even see a glove box light. It may have been removed prior to me?

Glove box light I think has to have the headlights on for it to come on. All FD's I think have glovebox lights. Could have been removed or something.

Dale

After testing everything to the best of my ability, I think I’ve determined it to be the cluster 😥 I have it removed and now have a 0.00 draw.

Congratulations. Good luck with the cluster. Still, you might want to check the continuity of the wiring to your rear hatch light to make sure it isn't shorted. Even with the bulb removed, an intermittent short would kill the battery. The hatch lamp is controlled by 2 switches in series - one in the lamp and the other in the trunk latch.

For all I know, your '92 might not have come with a glove box light, or it might have been yanked as Dale suggested, but for future reference, my '94's glove box light bulb is tiny. It is in a cheezy little grey plastic reflector up in the dash next to the the latch striker bar. The socket and bulb unscrews as a unit from the reflector with 1/4 turn. It's easier to see if you use a flashlight and mirror. The switch for the lamp is on the side (the left side on my car) of glove box opening, and has a little rod that is pushed up to open the switch when the door is closed.

But, if Dale is correct as usual, the glove box light alone wouldn't kill your battery because the exterior lights have to be turned on for it to work in the first place.

I’ll mess with the hatch light next to ensure there is no short, that was a good point thanks! I narrowed it down to a plug on the cluster, I removed all the bulbs and other plugs to see what if it was any of them but it wasn’t. When I removed the one plug it went from 110mA to 0mA

https://cimg0.ibsrv.net/gimg/www.rx7...25aba228d.jpeg
it was that plug

Interesting. That looks like connector 4 on the gauge cluster, page Z-42 through Z-44 in the wiring diagram for the 1994 US model. With that connector unplugged, try measuring voltage at each of the pins on connector 4.

4A should not have power with the key off, and the wire might not be present on manual-trans cars. It looks like it gets grounded by a water thermoswitch.
4B should not have power with the key off, this is the illumination circuit that dims the numbers and labels for most of the gauge cluster
4C should not have power with the key off, looks like this gets powered by the ECU (when the key is on) and grounded by the power steering pressure switch.
4D, I'm having trouble finding in the diagram also.
4E looks like it should have permanent 12V when the key is off. If I'm reading the diagram correctly this sends power to the speedometer board (from the 10A room fuse).
4F should not have power with the key off, it looks like this activates the Seat Belt lamp.
4G should not have power with the headlights off, it looks like this activates the High Beams lamp.
4H should connect to ground.
4I should not have power with the key off, this connects to the 'Battery' lamp and the alternator.
4J should not have power with the key off, this connects to the parking brake switch and the brake fluid level sensor
4K should connect to ground.
4L should not have power with the key off, this connects to the starter cut relay

Hmmmm.....try this.

- Plug the cluster back in
- Unplug the 2-wire grey connector to the alternator
- Test again

That circuit has the alternator warning light which has to be there for the alternator to work properly. A bad alternator can drain the battery. I'm wondering if it's the alternator since it's that circuit - unplugging that connector breaks that circuit that eventually goes to the grey alternator connector.

Dale

Wow that’s some very helpful information, thanks so much. I actually just sent my cluster to Gagne for some repair. I went over a few of the leads with him last night and they checked out ok but I didn’t go that in-depth. Is there another way to test my alternator without the cluster?

I would just wait for the cluster to come back, Gagne will have it back pronto.

Dale

I just chased down an issue with my alternator, in the beginning stages the alternator would draw power with the car off draining my battery. This was solved by having the alternator rebuilt with new components (~$100).

When it was drawing power the alternator would make a very slight buzzing noise. It had to be dead quiet with garage door shut to hear, put your ear right next to the alternator if you are checking for it. If any of the wiring leading to the alternator or the alternator case itself is warm to the touch that is another sign its drawing power

But, with the cluster out that circuit won't be complete and it might not do anything. Again, wait until the cluster gets back. But, good evidence that this can happen.

Dale

The S wire on the alternator is live, if there is a short or some faulty wiring associated with the L wire the alternator could still drain power with the cluster unplugged. Mine was doing it while getting no signal from the cluster.

All I'm saying is it's something to check, one more possibility to check off the list

I was looking at connector 4 on the diagram vs in my car and none of the wire colors matched up. I also compare to connector 3 and same thing nothing lines up. Is this a difference in JDM vs US? the colors on my plug readout R/B - R/G - G---- B- Br/Y- W/B and the other row is Blue- Blue/Y - B/R----R/W-W/B-B if that makes sense lol and one of the pins seems loose

I tried this with no change unfortunately. That would have been the easy fix lol

OK, so the cluster is back from Gagne and in the car?

Car starts/runs/drives OK? Alternator charging properly?

How are you seeing the current drain at this point?

Dale

yes. Cluster is back, car runs, starts drives no issue. With a multimeter it’s registering a 120ma draw with connector 4 plugged in. If I take it out, then no draw. I noticed the draw because after my car would set for 2-3 days the battery would be about dead. Idk if the connector is the same as usdm (mine is rhd jdm) just different colors, but pin 4J had a 3 volt reading with the key out. And another pin also had 3 volt reading. According to the chart of voltages vs grounds they should either be 0v or a ground.

Wondering if it could be ABS, that's one of the warning lights on that circuit. There's a relay for the ABS pump, it's on top under the cover on the pump. Pull that and see if it makes a difference. That's not an uncommon problem.

If not, go through each item that's on that connector - defroster, I think turn signals, a few other things.

Dale

are you referring to the abs relay under the fuse box cover? (60amp) if so, it seems it has been pulled. The old cluster did not have an abs warning light bulb, and the bulb was placed by Gagne and it is lit up...for obvious reasons I’m assuming

No there is a relay on the ABS pump itself. It's not obvious, there's a plastic cover that hides it. One time mine was buzzing with the car off, I removed and re-installed it and it's been fine ever since.

Dale

ohhhhh I did not realize that. I will check that when I get home from work this evening. I appreciate your help

Let's recap.

With the ROOM fuse out you get 0mA with key out correct?
And also 0mA when cluster is unplugged?

And buddy charged you to fix something that wasn't broken correct?

I was going through the thread and I want to be sure we're on the same page as far as colour coding.

You say 4J is the culprit. What colour is it? Is it Brown(Br)/Yellow(Y)? If not, what colour is it?

I'm not sure if you tried this:

Plug everything in.

Locate connectors X-06(CPU), C1-10(Parking Brake), C1-11(Brake Fluid)

Disconnect them one by one and test for draw.

Post results.

Also locate CPU #2, and locate E2-01 connector, unplug it and test for draw.

You're problem has to lie in one of these connectors.

correct...ROOM fuse out, 0 draw, with connector 4 out on cluster and the other 3 plugged in, 0 draw. Haha and thankfully the cluster was done by Gagne who has been a huge help during this whole thing and charged me only shipping to run through the cluster which checked out fine on his bench test (I’m not getting an odometer read out, it just lights up, no numbers) let me recheck the wires, there were 3 I believe that had 3v to them with the key out. It’s jdm so idk if the colors are different or not because they don’t line up to the diagram completely. I’m currently at work, but I will run through your check list you provided and report my finding on those, I really appreciate it!