increasing multimeter fuse rating

[12vshocker]

i was wondering why this is a bad idea or if it's a good idea(pretty sure it's not)

Last week I repaired a vehicle with failed glow plugs, to test the plugs I just did a resistance test, I currently don't own a stand alone amp meter, I have an amp clamp but the wiring wasn't very accessible. It did leave me thinking if a increased the fuse rating in my amp clamp to say 30 amps ( it's currently 10amps) I could of tested each glow plug at the multi plug confirming the integrity of the wiring and condition of the glow plug, I was even thinking about putting a mini circuit breaker on the test lead, just in case there was a short,

Please tell me am I a genius or an idiot or just over complicating things

 

[telectrix]

what's the highest range on your clamp meter? a close-up pic would help. a heater plug is about 120 ohms, so that's 10A each. you could just connect each one in turn and measure the current of each.

 

[12vshocker]

The amp clamp and multimeter have a fuse rating of 10amps, the glow plugs I was testing draw 18amps from cold, but what I'm interest in is what's the potential down fall of increasing the fuse rating in the multimeter

 

[telectrix]

meter meets skip.

 

[Des 56]

what's the potential down fall of increasing the fuse rating in the multimeter

meter meets skip.

Experience ?

 

[ruston]

Na he's to old a cat to be 'taken in' (insert your own description) by a kitten.

 

[12vshocker]

Ok so basically it will fry the meter. Guess I'm not a genius then

 

[telectrix]

just buy an AC/DC clamp meter with a higher range.

 

[Pat H]

The fuse in the meter is there to protect the components inside.
Current is normally measured over a large low value resistor.
If you upped the fuse you'd allow more current through the resistor and it would likely blow. Then its for the skip.

 

[12vshocker]

Could you use a shunt resistor in series to get a basic multimeter to measure higher current draw?

 

[12vshocker]

Oh wait that wouldn't work right because you would need to do a volt drop test after the glow plug to get a reading which isn't really possible

 

[telectrix]

your shunt resistor would need to be in parallel with the meter so it drew a proportion of the current. without knowing the meter's internal resistance on each range, the value cannot be calculated.

 

[12vshocker]

In hindsight my question was probably laughable, but your answers were awesome thanks for your help!

 

[ruston]

But is your question how to test a glow plug lol?

 

[12vshocker]

I'd be interested to hear how you would go about testing glow plugs

 

[ruston]

Well the easiest way is to leave them in the car , take the terminals and cables off , one probe of a resistance tester on the tip of the plug the other to the earthed body and read the resistance , if there is none they are goosed . the readings should all be about the same if they are healthy.
This method has limits as the tips can be burned away.
Ths correct way is to take them out-sometimes a pain , and do the same test but between the the terminal tip and the plug body.

 

[Specialist]

Resistance testing is always a good first step, but my preferred way is always a Current clamp or an old fashioned Wilkson Automotive Volts / Amps tester.

A used ac / DC clamp can often be had for around £20 - 25
The Wilkson around £50 - 60 depending on model & this will directly read either 60 or 100 amps dc, But needs to be placed in series with the load.

Please don't increase the fuse rating in your meter, the only thing that will happen is you'll see a puff of smoke as your meter goes Ouch & dies.

 

[ruston]

Yes if you have a clamp meter it is half the battle.
The older type though the tips used to burn away or be fouled up , although working to a degree did not do the job properly. If they were easy to get at my first choice was to take them out.

 

[Specialist]

My first choice nowadays is called a Roy (Well abused car mechanic, only 2 owners from new)

 

[ruston]

I'm called Roy too then lol.
I am going out this morning on a love job on bespoke electric steps on a taxi.
The harness is about 20 singles wires and they are all the same colour . They do have lettered ID on them but it is about every four inches . You've guessed it, it's in harness tape or flexible conduit in a place where Hitler couldn't find it. Plus there is a flat floor and seats built on top of the access I need.