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Hello everyone i have a 1987 Pontiac Firebird 4 barrel v8 and have been having a battery drain for a while now i thought it was the radio so i pulled the fuse and nothing changed if anyone has had a similar problem and knows how to fix it or what to look for please help me this problem is very annoying. I hear this is a common problem with GM vehicles
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It’s quite common on GM vehicles, but make sure its not the battery itself. Overtime, batteries get old and can’t hold a charge for a very long time. Leave it disconnected overnight or for a day, hook it back up and see if it starts. You can also get it tested at an auto parts store as well. If the battery checks out okay, then you might have to pull out more fuses to accessories to see whats draining it. Do you have anything aftermarket on the car?
Parasitic Drains are the worse, i spent days trying to figure out what caused mine until I found out it was a bad battery.
I once put a test light inline with the battery and made sure everything was off. Pull fuse from radio, bulb from under hood if you have one, doors closed. etc. Now if light is on then you have a short. I then started to remove fuses one at a time and putting back in till test light went out. I found interior light wire to have a short. You may be able to narrow it down.
I’m with wardak33 on this, check the battery first as that could be the problem. Also make sure the connections are clean and tight. If there is a parasitic draw your going to need a DVOM with the ability to read miliamps. You would need to disconnect the positive battery cable and place the leads on the battery post and the battery terminal in series, start with the hightest miliamp setting. Your looking for a reading at LEAST below .035miliamps, if it’s over that you have a draw on the system and you need to start puling fuses till the amp reading drops to normal levels. Once you pull a fuse and the readings drop you need to look at everything that fuse runs to find your draw. It can be a pain but that’s how it’s done. Good luck.
Iv checked out the battery and it is fine i did what Tri9SS suggested and started pulling fuses then when i pulled the 20 amp CTSY WDO fuse the test light went out. but it seems when i pulled that fuse the brake lights and hazard light stoped working i dont have a DVOM i should probably get one.
Hi JayByrd92,
Great info and followup. Now that you have isolated the fuse (and corresponding circuits), do all the brake lights and hazard lights work? I am assuming a short on the B+ side of one of those electrical lines would prevent a bulb from lighting up….there is already a path to ground through the short. I presume this fuse also controls the courtesy lights when you open the door? I would also check the courtesy lights near the floor (under the dash), if equipped. These tend to see “more action” with people getting in and out of the vehicle (potential for bumping into them, salt corrosion too). Good luck and be patience…you will find it! Keep us posted.
everyone one here is giving great advice. i had this same problem and mine was the cigarette lighter in my honda and chevy. i like to use a circut tester and pull fuses. i agree that the battery as well as the alternator should be checked. as well as connections for corrotion as that can have alot to play in everything to. i would check the connection wires for tares. good luck L:D
It does sound like your issue is in the brake light circuit and the switch would be a good place to start looking in my opinion. A good wiring diagram would be your best friend here to help you look for areas of where the fault might be.
Eric
HI glad you found a starting point, I found a problem with the mercury switch I believe you have one in the trunk and in the front hood that control on off function for those lights. I have seen them switches come loose and stay on with hood or trunk closed. , Make sure the hood light goes out or take out the bulbs and see if you still have a drain. good luck
I dont have lights in the trunk or hood and thanks to everyone who replied to this post it has been a big help but im not exactly sure what im looking for all of the brake and hazard lights work. what should i look for regarding the electrical short? a broken insulation in the wire or a wire that is touching metal? i suck when it comes to electrical problems.
If you go to Autozone.com, you can sometimes find wiring diagrams for some vehicles. I would start there and see which circuits are on that fuse you have pulled that stopped the drain and go from there.
You could even try to post a image here of the wiring diagram and we can also help you out that way too!
Without a diagram you are kinda in the dark. Set up your test light the same way you did when you pulled the fuses. unplug you brake lg switch on the brake pedal. watch for the test lg to turn off. If it does not go out then the problem is most likely not in your brake light sys. But you cant be forsure with out a diagram. start with a power distribution diagam.
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