ignition live and milliamps

mhuk · May 12th, 2020, 21:40

My multimeter is duff. It's not giving any amp readings and inside it's got wet in the shed at some point so it's a bin job. The voltage part still reads.

Question. If my ebay cheapo GPS speedo gauge works when connected to the car battery terminals but not when connected to the ignition live @ 11.5V then does that mean my ignition live gives off less than the required 100mA? I get nothing from the gauge. This is from a unused plug taped with the cluster loom.

I'm a dumb blonde with electrics tbh.

Also, when i connect my new multimeter (it's on way) I do connect the probes to the correct sockets on the meter and put the probes into the circuit to get the reading. I looked on youtube and it seems to be correct.

Cheers

aardvarkash10 · May 12th, 2020, 22:40

If the car runs, the ignition + is well capable of delivering 100mA

Are you SURE the socket you have connected to is IGN+?

Your second question depends on whether you are testing a voltage or current.

Checking voltages is done "in parallel" with the circuit. Typically you are measuring between earth and the test point. Probe leads connected to the correct sockets in the meter, then meter set to the correct scale, then place the earth probe (typically black) on a known good earth, then probe the test point with the other lead (typically red).

Checking current is done "in series" - you have to disconnect the cirucit you are testing, place the meter "into" that disconnection. Probe leads connected to the correct sockets in the meter, then meter set to the correct scale, then place one probe into the "supply" side of the disconnection, and hte other probe into the "load" side of the disconnection.

Typically a multimeter used to measure current is limited to about 10A. You'll be able to test a single headlight circuit, but not both together. Normally they are fused, and any attempt to measure outside its range (or if you forget its on Amps and try to check a voltage...) the fuse will blow.

https://www.youtube.com/watch?v=c9KNAIjoEYs

Laird Scooby · May 12th, 2020, 23:19

What Ash said ^^^^^! Saved me a lot of typing Ash!

mhuk · May 12th, 2020, 23:25

If i stick my probe in i get a voltage reading when ignition is on or engine engine running.
Key out and its dead.

Twke the gauge to the battery and connect the same wires and its working. Only diff is .5v drop in the car but gauge is rated to work from 9v.

Ill look at the vid tomorrow.

Cheers

Martin

mocambique-amazone · May 13th, 2020, 09:04

Quote:

Originally Posted by mhuk

If i stick my probe in i get a voltage reading when ignition is on or engine engine running.
Key out and its dead.

Twke the gauge to the battery and connect the same wires and its working. Only diff is .5v drop in the car but gauge is rated to work from 9v.

Ill look at the vid tomorrow.

Cheers

Martin

I can't remember this socket at this moment. Where it belongs to?
Maybe you grabbed a 12v wire by the ECU/EZK or ABS. Signal line, no amps here.

Good luck, Kay

mhuk · May 13th, 2020, 11:22

no idea where it goes. I think you could be right. I now got a 10 mile cycle to get the new meter.

Update later. Thanks

TonyS9 · May 13th, 2020, 13:36

Measure the voltage where the gauge doesn't work. If there is not enough current capacity (or too much resistance) the voltage will drop to below 9V.

If you are measuring at the same time as connecting the GPS speedo, then its spec is clearly a lie. Starting the engine should increase the voltage though.

mhuk · May 13th, 2020, 15:19

I used another ignition live and it’s fine. I measured the mA aww pics. Thank you chaps.

Cheers chaps

mhuk · May 13th, 2020, 15:22

Pics here

May 12th, 2020, 21:40	#1
mhuk Senior Member Last Online: Mar 1st, 2024 08:41 Join Date: Mar 2009 Location: London	ignition live and milliamps My multimeter is duff. It's not giving any amp readings and inside it's got wet in the shed at some point so it's a bin job. The voltage part still reads. Question. If my ebay cheapo GPS speedo gauge works when connected to the car battery terminals but not when connected to the ignition live @ 11.5V then does that mean my ignition live gives off less than the required 100mA? I get nothing from the gauge. This is from a unused plug taped with the cluster loom. I'm a dumb blonde with electrics tbh. Also, when i connect my new multimeter (it's on way) I do connect the probes to the correct sockets on the meter and put the probes into the circuit to get the reading. I looked on youtube and it seems to be correct. Cheers __________________ Volvo 940 19T, Charge cooled, Chipped.

May 12th, 2020, 23:19	#3
Laird Scooby Premier Member Last Online: Today 20:44 Join Date: May 2012 Location: Lakenheath	What Ash said ^^^^^! Saved me a lot of typing Ash! __________________ Cheers Dave Next Door to Top-Gun with a Honda CR-V & S Type Jag Volvo gone but not forgotten........

May 13th, 2020, 11:22	#6
mhuk Senior Member Last Online: Mar 1st, 2024 08:41 Join Date: Mar 2009 Location: London	no idea where it goes. I think you could be right. I now got a 10 mile cycle to get the new meter. Update later. Thanks __________________ Volvo 940 19T, Charge cooled, Chipped.

May 13th, 2020, 15:19	#8
mhuk Senior Member Last Online: Mar 1st, 2024 08:41 Join Date: Mar 2009 Location: London	I used another ignition live and it’s fine. I measured the mA aww pics. Thank you chaps. Cheers chaps __________________ Volvo 940 19T, Charge cooled, Chipped.

May 12th, 2020, 22:40	#2
aardvarkash10 Master Member Last Online: Oct 8th, 2022 22:22 Join Date: Sep 2016 Location: Auckland	If the car runs, the ignition + is well capable of delivering 100mA Are you SURE the socket you have connected to is IGN+? Your second question depends on whether you are testing a voltage or current. Checking voltages is done "in parallel" with the circuit. Typically you are measuring between earth and the test point. Probe leads connected to the correct sockets in the meter, then meter set to the correct scale, then place the earth probe (typically black) on a known good earth, then probe the test point with the other lead (typically red). Checking current is done "in series" - you have to disconnect the cirucit you are testing, place the meter "into" that disconnection. Probe leads connected to the correct sockets in the meter, then meter set to the correct scale, then place one probe into the "supply" side of the disconnection, and hte other probe into the "load" side of the disconnection. Typically a multimeter used to measure current is limited to about 10A. You'll be able to test a single headlight circuit, but not both together. Normally they are fused, and any attempt to measure outside its range (or if you forget its on Amps and try to check a voltage...) the fuse will blow. https://www.youtube.com/watch?v=c9KNAIjoEYs

May 13th, 2020, 13:36	#7
TonyS9 Premier Member Last Online: May 19th, 2024 20:22 Join Date: Jul 2009 Location: Holywood	Measure the voltage where the gauge doesn't work. If there is not enough current capacity (or too much resistance) the voltage will drop to below 9V. If you are measuring at the same time as connecting the GPS speedo, then its spec is clearly a lie. Starting the engine should increase the voltage though.

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