Today at Atelier Kaz - ex-Honda R&D, F1, Indy/CART engineer

Long time ago, when I got this USB power adaptor, I noticed that the bimetal terminal was pushed away that the cigarette lighter was no longer engaging and just pops back to its normal position.

Not a problem as I don’t smoke but got concerned of potential damage to the bimetal terminal.

By the way, you can manually pull the bimetal terminal inward if you ever want using the lighter function as the heat sorce. With the IG key out of the key cyl, just gently bend the terminal inward but not too much.

Make sure that the lighter pops back to its original position within 5 – 10sec otherwise, the thermal fuse protection may engage resulting in open circuit.







With modern cars equipped with 'accessory power socket' and the 'cigarette lighter' becoming an optional accessary,
many aftermarket plugs are designed without the consideration for the bimetal terminals nowadays.

Thus, as mentioned above, it can push away the 2 bimetal terminals.








Majority of them have spring loaded centre terminal (as shown with my finger) with fuse enclosed.
Some are not even spring loaded so just direct contact to the centre terminal of the socket.

Very rare to cause short circuit but there is only a few mm gap between the GND socket wall and the bimetal ACC positive terminal so be careful.

Never had problem but if something failed inside the accessary plug, it can create short circuit if the distance between the yellow 2 lines were less than 7.5 – 10mm.
And you need to consider the variant as part of the plug centre terminal may sunk inside the recessed/dimpled brass socket terminal.













In my view, although the cigarette lighter socket is fused at 20A, it should only be used as the power outlet if the current/power consumption rated at much lower.
This is because the brass rivet holding the bimetal positive terminal has recess/dimple (blue arrow) that the plug side of the centre terminal may not make good contact.

With the OEM tyre air pump, couldn’t find the spec but being as standard electrical motorised pump, must have huge current consumption.

The centre terminal of the plug has really large diameter with fairly flat shape making good contact against the socket.

Never seen such decent design on other aftermarket plugs.