Car wont start but new battery tests OK

[Sir_jagworth_Sutch]

1. My model of MX-5 is: __NB Nevada
2. I’m based near: Wincanton
3. I’m looking for technical help or recommendations on: __Charged new baettry before fitting. Engine would not start - clicks only.
4. AA called, tested battery, FAIL
5. Car started ok by AA using booster
6. Returned battery for replacement, but it tested fine under load - volts and cranking power
7. Next steps?

[coconino]

Not wanting to knock the AA patrol or teach you how to suck an egg but give both battery terminals a good clean with the cables disconnected and then clean the contact area of both the terminals on the cables. Reconnect and fingers crossed.

Cleaning battery terminals, wow! Who'da thunk it made such a difference?

Had this NC3 since Jan & is generally running very well. In recent weeks tickover ( whilst still smooth) has dropped a little to 700-750 rpm & car feels on the verge of stalling in manoeuvring & some heavy traffic type situations. Also a little rough pulling away sometimes. OBD2 was whinging about low voltage- 13v, not completely shabby! Fearing dying battery & or alternator I applied the voltmeter this morning. All good batt=12.6v resting & alt putting out a healthy 14.1v. Noticed a small amo…

If that doesn’t work then try and find someone else to test the battery (does the battery supplier have another branch in travelling distance?).

[Sir_jagworth_Sutch]

It’s a brand new battery!

[Jimgell]

See if there is a date code somewhere. Sometimes a ‘new’ battery has been in storage for several years and may not have been cared for properly.

[Sir_jagworth_Sutch]

Hi everyone, Probmen solved.
Re-fitted the battery again this morning, and car started first time. Probably because I was wearing posh trousers for once. I really am confused!

[coconino]

I suspect that one of the cable terminals needed cleaning and the motion of removing and refitting the cables has cleaned the contact area and improved the connection. As for the AA diagnosis, the AA patrol may have tested the battery through the cable terminals thus getting a faulty battery reading.