Car tyre pump won't work off mains adaptor

[Lobster]

I recently had occasion to charge my central heating expansion vessel (qv!), and tried to use the little 12V pump which I carry in the car for inflating tyres. As we have a 240V->12V PSU for use with a camping fridge. This device states that its output is 13.6V DC / 5A /68W - surely more than adequately rated for the pump? (or maybe not?) Anyway, plugged in, the pump simply cycled weakly at about once per second.

So purely from curiosity, why would the pump have failed to work on the transformer?

David

[Ian Stirling]

The pump takes >>5A to start, and the power supply is switching itself off to prevent damage.

[Dave Plowman (News)]

Probably can't supply the peak current needed. Although the motor may be rated at 5 amp continuous it may take a great deal more for a very short time each compressor cycle or whatever.

[robert]

ISTR that my 12v car tyre pump took about 9amps !

Its not alot slower using a footpump

Robert Robert

[Lobster]

Blimey - wouldn't have guessed. That would explain it...

You want to try using a footpump when the valve you're inflating through is 6 feet off the ground (and you have to pump an 18-litre volume up to

4 bars. (But job done - good fun!)

[kimble]

I'll second that. I got sick of mine blowing the 10A cigarette lighter fuse every other time I used it, so lopped the plug off and fitted a pair of crocodile clips for direct connection to the battery.

Given a spare car battery, this means I'm all set up for topping up an expansion vessel 6ft off the ground, thus ensuring that my expansion vessel will remain happily inflated until about a week after the pump spontaneously combusts.

Kim.

[Dave Plowman (News)]

With Xmas coming, one of those jump start packs with compressor built in is worth a punt. It's also a convenient easily portable source of 12 volts for testing car bits, etc - better than a spare battery. I got one from Lidl for 20 quid and didn't expect it to last. But it's done ok.