Battery drains overnight while parked

Tiny
SWG1619
  • MEMBER
  • 1992 MAZDA MIATA
  • 1.6L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 67,000 MILES
Recently, when I leave the car over night, the battery drains out. My mechanic located the circuit that is drawing power and it happens when either door is closed. The only things that appear to be on that circuit are the two interior dash lights (I do not have a dome light) and the radio. Now the radio was installed professionally about a year and a half ago without any issues until possibly now. No CD player. My question is, since the draw stops with the doors open (and the light switches turned off) what could possibly be causing this drain? Anything else on that circuit I'm missing? There is a cigarette lighter but no lighter is in it. It's only used to charge my phone and that is unplugged at night. I really appreciate your help!
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Friday, November 13th, 2020 AT 6:17 PM

134 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good evening,

The first thing he should have done is to disconnect the radio from the circuit and see if the battery still goes down overnight. If it does, that was not the issue.

https://www.2carpros.com/articles/car-battery-dead-overnight

What was the fuse number and location so I can get a diagram of that circuit?

Roy
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Friday, November 13th, 2020 AT 6:39 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

That is an odd one. Tell me this. If you turn the interior lights off at the light assembly, is there still a draw?

I'm looking through the wiring schematic, and power is direct to the door light switches and via the light assemblies. When the door switch closes the circuit (meaning the doors are open) then power is allowed to go to the ground and turn on the lights. Has anyone checked to see if there is a wire being pinched causing a short and drawing power?

Take a look at the attached schematic. Try turning off the lights at the assembly and let me know if the draw stops. That way, I'll know on which side of the switch to check.

Take care,
Joe
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Friday, November 13th, 2020 AT 6:47 PM
Tiny
SWG1619
  • MEMBER
Thanks for your quick response! I can't read the diagram but he said it's the "Room" fuse. He still has the car and I'll be picking it up tomorrow morning. But the lights do not come on when the door closes. Are you telling me to just turn the switch to the off position?
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Friday, November 13th, 2020 AT 7:12 PM
Tiny
SWG1619
  • MEMBER
Room is "N" fuse from what I can see?
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Friday, November 13th, 2020 AT 7:20 PM
Tiny
SWG1619
  • MEMBER
Sorry! Just was able to enlarge your diagram. 14
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Friday, November 13th, 2020 AT 7:22 PM
Tiny
SWG1619
  • MEMBER
He told me that it didn't matter if the light's were turned off at the switch. The draw stops when the door is open. He didn't disconnect the radio. Lights do not come on though when the doors are shut. Room fuse#14, when pulled stops the draw. Unfortunately he said he's not an "electrical" guy so he did not check for any pinched wires. Where should I check for those?
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Friday, November 13th, 2020 AT 7:26 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

The first thing I would be checking for would be for a pinched wire. If you can picture in your mind, when the door is opened, there are contacts in the switch that come together (close) and make contact. That is what allows power to flow and turn the light on. When the door is closed, the connectors in the switch come apart (open) so power can no longer flow. Based on that, the power has to be going somewhere or one of the switches is bad and allowing power to continue. However, I would think that should cause the interior lights to stay on.

Regardless, try disconnecting the (one at a time) the connector to the door jamb switch. See if that chances anything.

Let me know.
Joe
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Friday, November 13th, 2020 AT 7:46 PM
Tiny
SWG1619
  • MEMBER
I know exactly what you mean. I'll see if I can get my mechanic to do it tomorrow before I take it back. Otherwise, I'll try to do it myself. I can get back to you in a couple of days? And, thank you!
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Friday, November 13th, 2020 AT 8:00 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
You are very welcome. Let me know what you find out or if you have other questions.

Take care,
Joe
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Friday, November 13th, 2020 AT 8:17 PM
Tiny
SWG1619
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You too!
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Friday, November 13th, 2020 AT 8:21 PM
Tiny
ASEMASTER6371
  • EXPERT
From your description it does sound like the radio may be the root cause of failure.

When you open the door, it should cause a instant draw.

Roy
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Saturday, November 14th, 2020 AT 3:59 AM
Tiny
SWG1619
  • MEMBER
Hi Roy!

Just got my car back this afternoon. We went through it a little. I'll tell you, as far as a bent wire in the door? The door switches are on the back door jamb and the wiring actually goes around the back of the car. Not through the front where they might become pinched. I have to pick up a volt meter, and find it myself somehow. The cigarette lighter, which I believe is also on that line, appears to stay off also with the doors closed but again, I'll have to check with the volt meter. If I can! I installed a battery shut off switch in the meantime so there will be no overnight drain. Only other option I think is having an electrical expert try to track it down? I don't know? It's frustrating as hell! My mechanic didn't want to do it! I've known him for 35 years and he just doesn't have the time to look for a short for hours on end. Maybe an electrical expert?
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Saturday, November 14th, 2020 AT 9:46 PM
Tiny
ASEMASTER6371
  • EXPERT
Did you disconnect the radio and see if it still has the drain?

Roy
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Sunday, November 15th, 2020 AT 1:38 AM
Tiny
SWG1619
  • MEMBER
My mechanic said he couldn't find where that was connected to check it. I guess I'm going to be the one to try it. I don't know, but I think my guy has been at the job so long, he doesn't want to be bothered with stuff like this. So, it's me or a so called electronic expert. But if it takes a mechanic all day to find the problem, it could cost me an arm and a leg. Have any suggestions for a decent inexpensive volt meter? Anything else you can recommend? Thanks so much!
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Sunday, November 15th, 2020 AT 5:32 AM
Tiny
ASEMASTER6371
  • EXPERT
All he has to do is remove the radio and disconnect it.

This sounds like you need another technician. This guy does not sound like he wants to help you.

I attached a YouTube video of the removal of the radio.

https://www.youtube.com/watch?v=x_qdRj8jgBw

Roy
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Sunday, November 15th, 2020 AT 5:43 AM
Tiny
SWG1619
  • MEMBER
You are correct! He said, "I don't have time to do it and I don't want to break anything". I've put a few radios in years ago. Before I take the dashboard apart, any chance of just finding the power lead coming from the back without taking the dashboard apart?
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Sunday, November 15th, 2020 AT 5:56 AM
Tiny
ASEMASTER6371
  • EXPERT
You need to pull the radio and disconnect it from the back. That will tell us if it is the radio.

Roy
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Sunday, November 15th, 2020 AT 6:00 AM
Tiny
SWG1619
  • MEMBER
I'll watch the video and try to find if that's it. You have an inexpensive volt meter recommendation?
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Sunday, November 15th, 2020 AT 6:18 AM
Tiny
ASEMASTER6371
  • EXPERT
You can go to any parts store and get a cheap one. That is all you need.

Roy
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Sunday, November 15th, 2020 AT 6:44 AM
Tiny
SWG1619
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Great! Thanks
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Sunday, November 15th, 2020 AT 6:57 AM

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