2012 Edge Strange electrical problem, how do I diagnose it?

[Mike Scir]

My neighbor has a 2012 Edge that kills the battery pretty quickly, I think it goes from fully charged to unable to crank the engine in one or two days. (there is a bit of a language barrier but we usually manage). He replaced the battery 3 weeks ago but no change. He took it to a shop that tested the alternator and they said it was good. 

 

Electrical problem history: 
First he said the interior light would not always go off when the driver side door was closed. 

Then he said an engine compartment fuse blew, I looked it up and it appears to be the #18 40A HVAC blower motor, it looks melted and fused. 

Then he mentioned that he heard a buzzing or clicking sound from the engine compartment fuse box and indicated where he thought the noise was coming from but I didn't find any bad fuses in the immediate area, also pulled several, including a black box that might be a relay, that didn't prevent the next symptom from happening. 

 

This is the interesting part: 

I got a voltmeter and without the + cable attached the battery measures 11.4V. With the + cable attached it oscillates between roughly 5.3V and 4.1V about once per second. 

Does these symptoms make any sense to anyone? While to me, on the surface they appear unrelated (door interior light, HVAC fuse, oscillating battery drain) maybe this all makes sense to someone. 

He said there were zero problems that he was aware of when he purchased the vehicle. 

 

Note: The owners are low income and said if I can simply disconnect problematic circuits but the car will still run normally ans safely and pass smog, they'd be happy with that, if the repair would be costly (more than say $200). 

 

Thanks in Advance,
MIke

Edited 11 hours ago by Mike Scir

[1004ron]

9 hours ago, Mike Scir said:

This is the interesting part: 

I got a voltmeter and without the + cable attached the battery measures 11.4V. With the + cable attached it oscillates between roughly 5.3V and 4.1V about once per second. 

Battery appears to be past its useful life.

 

Charge it and then take it to a place like Autozone for them to do a health check on it, free of charge.

 

.

Edited 5 hours ago by 1004ron