Battery Keeps Dying after Repairs [Solved] - 2005 Chevrolet Tahoe
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Here is a list of tools I use every day at the shop. Let me know if you use them too in the comments!
General Information:
This 2005 Chevrolet Tahoe came into the shop for a suspected battery draw. The customer states that even with a new battery, it won’t hold a charge overnight.
First Thoughts:
I have worked on so many vehicles with battery drains and shorts, it’s not even funny.
I have seen alternators completely drain a jump box in seconds because they are severely shorted.
I have seen aftermarket radios stay on all the time, draining the battery.
I have even seen a tiny button on the driver seat become stuck and cause a battery to drain.
But this vehicle takes the cake.
It did not take long to figure this one out, but it’s just crazy what was causing this issue.
Diagnostics:
There wasn’t much diagnostics with this vehicle and you’ll see why.
The first step I do with any battery drain diagnostics is begin with a fresh battery.
I will usually put a new battery into the vehicle and let the customer’s battery charge for some time.
When connecting the new battery, I noticed a clicking noise happen, like something was clicking on.
It would happen every time the battery was connected before the battery drain was resolved.
I didn’t realize it, but this was my first clue.
My next step is to connect my amp meter to read what amperage is draining from the battery.
I use “The Hook” made by Power Probe. It is my go-to battery drain tester.
The third step is to sit and let the vehicle go to “sleep”.
“Sleep” is when all the modules power down in the vehicle.
When in “sleep mode” the battery drain is roughly 0.050 amps.
Letting the vehicle go to sleep can take upwards of an hour depending on the vehicle.
On this vehicle though, the amperage flowing from the battery was much higher than 0.050, which indicated a draw. I did not take a picture of “The Hook” on the Tahoe and don’t remember exact numbers. Sorry!
Since this Tahoe indicated a draw, I moved to the next step, which is to measure voltage drop across the fuses.
But there was something that stopped me.
Do you see what stopped me?
This picture above was taken immediately after I opened the lid to the fuse box.
There is a wire in place of the A/C clutch relay!
Every time the vehicle has power, it engages the A/C clutch.
That is what the noise was every time the battery was connected and that is the draw of this Tahoe!
After questioning the customer a little more, it was revealed that a “mechanic” friend fixed his A/C and it has been killing the battery since.
This is not “fixing” the A/C.
After removing this wire from the A/C clutch relay and replacing it with the correct relay, the draw was gone and the battery did not die overnight. Fixed!
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