Shop says its the battery….REALLY?

[Josh G]

’06 Hyundai Sonata

My friend’s girlfriend’s car wouldn’t start so I offered to take a look at it. After doing some tests my friend and I thought it was the starter solenoid (or connection). She wanted a second opinion, and the shop she took it to says it’s the battery, but I’m really suspicious of that diagnosis and here’s why…

When the key was turned you could hear the click of the starter solenoid and then nothing else would happen (the solenoid wasn’t clicking rapidly like with a weak battery, it just made a single click as it engaged).

When I first got to the car I also suspected the battery, so the first thing I did was test it. I saw that battery voltage dropped from 12.6 to 11.5 as the solenoid engaged. Then I measured the solenoid current and saw that is was a regular 34 amps and the current waveform looked pretty clean. It appeared to me that the solenoid was engaging fine but not transferring power to the starter motor (dirty contacts or lose connection maybe).

Then I was trying to get another current reading and I moved the starter wire some when I put my clamp around it and then the car fired right up like it was brand new. So loose connection/corrosion somewhere or maybe the repeated “hammering” of the solenoid contacts finally caused them to make a connection.

But a bad battery??? :blink: Am I missing something? Every time I’ve come across a bad battery it stays bad. It doesn’t all of the sudden just start firing up the car again (unless there’s a temperature change which there wasn’t).

Also if the battery was bad I think I should have seen voltage drop much lower than 11.5. A bad battery either can’t engage the solenoid so you hear rapid clicking or if it can engage it then the starter will be really weak. Either way I would have seen voltage drop to below 9.6

What do the experts out there think?

Topic

[Jim Davis]

Seems you found the problem, loose connections. But It also seems you need to do a better load test on the battery so she will not be left out in the cold. A simple voltage drop test may not give you the whole picture of its health.

[Lorrin Barth]

Yeah, a load test on the battery might reveal something there. I’ve encounteed batteries that have had bus break inside. These will still read the correct voltage but deliver little current. However, I’m willing to accept the 12.6 volts as good battery for now.

The solenoid is making contact or you wouldn’t see 34 amps, the solenoid pull in winding isn’t going to pull much. So, it could be high resistance battery cable connection, high resistance solenoid contact or brushes in the starter worn down to a nubbin.

[none]

There’s a lot of places that use a handheld battery tester that doesn’t actually ever load the battery, it just makes an educated guess as to the battery’s condition. That could be where the shop’s assessment came from.

[Josh G]

[quote=”barneyb” post=130047]Yeah, a load test on the battery might reveal something there. I’ve encounteed batteries that have had bus break inside. These will still read the correct voltage but deliver little current. However, I’m willing to accept the 12.6 volts as good battery for now.

The solenoid is making contact or you wouldn’t see 34 amps, the solenoid pull in winding isn’t going to pull much. So, it could be high resistance battery cable connection, high resistance solenoid contact or brushes in the starter worn down to a nubbin.[/quote]

I don’t have enough experience with solenoids to know what their normal current is (it’s impossible to measure it on a working assembly because the starter motor current makes it impossible to see), but I did read an article somewhere that made me think 34 amps could be perfectly normal depending upon the design. But either way I completely agree that it all still adds up to a solenoid problem

[Josh G]

[quote=”no_common_sense” post=130059]There’s a lot of places that use a handheld battery tester that doesn’t actually ever load the battery, it just makes an educated guess as to the battery’s condition. That could be where the shop’s assessment came from.[/quote]

Yeah that was my suspicion also…and it’s not even like I’m saying they were wrong. Maybe the battery did test weak, but I didn’t agree with them calling it a fix. The owner needs to drive it to Florida tomorrow.

I know there is a lot of debate on the proper way to test a battery and I know I didn’t do the best test, but I was out of the shop and working with what I had. In my mind, there is no way (based on how I saw the battery behave) that the battery can be blamed for everything we encountered during our diagnosis.

Also I’m taking note of the fact that the battery started the car like a champ halfway through our troubleshooting so that also makes the bad battery call questionable to me.

[Josh G]

Well the car broke down again 100 miles outside of Savannah, Georgia. It was then towed to a shop and they replaced the solenoid/starter….like I was saying…. :whistle:

[Author]

Replies