1.5 Amp Fuse keeps blowing in my car

You could possibly measure the current, or is that a bit technical?

martin

With a little direction I can do it - I have 3 meters bascially your

39.95 type but I'm sure I can do it - what do I set my meter to when you say measure the current -

Thanks

put in a 3 amp fuse. The splitter seems to be able to handle it and you won't be plagued with nuisance blowouts. If the GPS is truly failed it will blow the 3 and you will need to troubleshoot the GPS unit. Otherwise the upstream wiring should be just fine. many people seem to believe that fuses are to protect the load device when they are really to keep the upstream wiring from burning up.

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Actually what I failed to mention was I plug the charger in to the 12V power outlet without plugging the other end into the GPS and it blows the fuse - it has something to do with the power source in my car not the GPS unit - in other vehicles it does not blow the fuse

Thanks

It seems like the charger is causing a momentary surge, possibly because of a capacitor charging up. The vehicle that does not cause a problem may have some sort of series resistance or inductance that limits this surge. It would be difficult to measure this surge without a storage scope or peak reading meter. You should be able to use, perhaps, a 1 amp slow blow fuse. You could also add maybe a 1 ohm resistor in series, or a hash choke. There are also surge limiting thermistors that start at a couple of ohms and then drop to about 1/10 that when they get hot.

Paul

I will try both - 2 questions - Can I use a 1.5 Amp slow blow or did you recommend a 1 AMP slow blow instead of 1.5 for a reason. Also when you say in series can I simply put a 1 ohm resistor on the + positive side of the female power outlet the charger plugs into

Thanks

The 1 amp gives a better safety margin, but 1.5 amps should be OK. The wiring will be protected in either case.

The resistor would go between the 12 VDC source and the outlet. The fuse would also be in series. If you disconnect either the fuse or the resistor, the circuit will be open.

Also, make sure the power plug does not somehow short out the connector as it is being inserted. Especially if it is not a standard type connector for

12 V power.

Good luck,

Paul

A slow blow fuse?

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Paul thanks for your time & help

I will try both

That might not be very helpful. Your meter might be able to measure the steady state draw of this charger. But I suspect that what is blowing your fast acting fuse is the charging current of a capacitor in its input stage. You'd need an oscilloscope to see that.

Try replacing the 1.5 A fast acting fuse with a slow blow type (same rating).

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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Better is to cure the 'power on' surge with a component called an 'inrush current limiter'. It starts with higher resistance, then resistance goes lower. Inrush current limiters are standard and plentiful for 120 volt appliances (that have lower current draw). They may be harder to find for your higher current. If not an inrush current limiter, then Paul Hovnanian's slo-blo fuse recommendation is a better solution.

Also a warning. Some 12 volt plugs short out (therefore blow any fuse) when put in some 12 volt auto power receptacles.

reminds me of a myth on mythbusters about someone replacing a blown fuse with a bullet ....

Colin =^.^=