12v sockets stopped working after I plugged in tyre inflator

[kissinger]

I know the likely culprit is a blown fuse, which I will replace, but do I need to replace it with a different kind of fuse in order for these sockets to be able to handle the tyre inflator (and is that even possible)? Also is it safe to plug this into another vehicle's 12v socket, or is it likely to blow the fuse on that too?

TIA

[vikingaero]

Once you replace the fuse, try a different tyre inflator. If it works without blowing the fuse, then it's more likely to be a defective inflator

[kissinger]

I was tempted to try the inflator in another car but I’d better not then. Thanks.

[anonymous-user]

I would only replace the fuse with the correct amp rating, otherwise you could end up with fried electrics or worse. Check the amp rating on the inflator too. If it’s bigger than the fuse you are replacing, you know the problem. If not, the inflator has a fault.

[kissinger]

The amp rating on the inflator (it's one of the generic Aircom VAG group box ones) is 12.5A. The fuse on the car is 15A. Does that mean that's not the problem, or is 12.5A too close to the max?

Our other car has a rating of 25A on all the 12V sockets. Is it safe to try the inflator on the car with the higher rating, just to see if it works?

[Decky_Q]

The fuse rating is matched to the thickness of wire going to the 12v socket. If the wiring is rated for 15A I wouldn't advise increasing the fuse rating above this.

I have sockets rated from 15A to 40A but the high output sockets have matching thickness and length of wire to safely supply them.

Replace the fuse with the correct 15A and try again, if it blows again I'd dump the compressor and get a replacement.

[kissinger]

Will do. Could it also be something to do with how you use the compressor? IIRC I didn't have the engine running at first, I just had the electrics on. I don't know if that would matter.

[hellorent]

You will have no issues changing it to a 20amp fuse, it will still pop the fuse well before doing any damage to wiring etc

[Krikkit]

kissinger said:

Will do. Could it also be something to do with how you use the compressor? IIRC I didn't have the engine running at first, I just had the electrics on. I don't know if that would matter.

It might be sufficient to stop the fuse blowing - the voltage will be nearly 20% higher if you have the engine running, with a proportional drop in current required.

[Decky_Q]

Cigarette lighter sockets are prone to voltage spikes when starting the engine (usb chargers left in long term can go pop due to this) so it's possible that this was the cause (I have done the same as you and not had a problem but who knows). If you replace the 15A fuse and try again you will either have solved it or be in no worse a situation.

[untakenname]

kissinger said:

Will do. Could it also be something to do with how you use the compressor? IIRC I didn't have the engine running at first, I just had the electrics on. I don't know if that would matter.

Should have the engine on or and dependent on idle voltage perhaps apply some revs till it reaches 14v or use the car first so the battery has a float charge, I've got a voltage meter in my car and whilst cranking when the cars been standing overnight the engine the voltage usually sags to 9.8v.

[kissinger]

I got a replacement inflator (exact same model) and tried it after replacing the fuse. Works fine (although I had the engine running this time). Although strangely the original one still doesn't work. I can only assume that when the fuse blew in the case when I first tried it, the inflator died as well, or was already dead?

[anonymous-user]

kissinger said:

I got a replacement inflator (exact same model) and tried it after replacing the fuse. Works fine (although I had the engine running this time). Although strangely the original one still doesn't work. I can only assume that when the fuse blew in the case when I first tried it, the inflator died as well, or was already dead?

sounds like the inflator has a fault/internal short which blew the fuse. Does the inflator have a fuse?

[kissinger]

Couldn’t tell you. Can’t see a way in to the thing.

[peterperkins]

Prise out the little rubber feet might be screws under them.

[Smint]

My twin cylinder inflator takes way more current than a cig lighter could provide, it was never intended to have a cig lighter fitting but came with croc clips for direct battery connection, even 2 minutes of use the heavy duty wires are getting warm to the touch.

I'd stop using the cig lighter for tyre inflating etc, fit a pair of croc clips and go direct to battery jump pack or even a disused battery you keep for such tasks.

[E-bmw]

Most likely the fuse would be inside the cig lighter adaptor.

[Dogwatch]

E-bmw said:

Most likely the fuse would be inside the cig lighter adaptor.

This. Sometimes one end of the fuse (usually wire-in-glass) is the centre contact on the plug, or fits into a metal cap which then forms said contact.