Can you measure amps on a power supply with a multimeter across the positive and negative posts

To check for power or continuity when you have a fire trouble code on the display panel and all the lights are out, you can use a multimeter. A multimeter is a handheld device that can measure electrical current, voltage, and resistance.

To use a multimeter to check for power or continuity:

Set the multimeter to the correct setting for the type of measurement you want to take (e.g. voltage, resistance, continuity).

Turn off the power to the circuit you will be testing.

Connect the multimeter probes to the appropriate points on the circuit. The red probe is usually used for positive connections, and the black probe is used for negative connections.

Turn the power back on and observe the reading on the multimeter. If the reading is within the expected range, there is continuity or power present in the circuit. If the reading is outside the expected range, there may be a problem with the circuit.

I hope this helps! Let me know if you have any other question.

If the battery is good
You have a parisitic draw somewhere:

Switch your Digital Multimeter to DC AMPs. Amps is usually indicated by an "A" on the Multimeter Switch. AC is usually shown as a "~" symbol and DC shown as a "-" symbol. You usually have to move the Multimeter positive lead to a separate socket on the Multimeter. Sometimes there are 2 sockets, a high range and a low range. Always test on the highest setting first. For example: high setting on your multimeter may be 10 Amp. Test on the 10 Amp setting first, then if the current drawn is less than your Multimeter Low setting, move to that setting and keep testing. In my example my Multimeter low setting is 0.3 Amps. Also indicated as 300mA (mA x 1000 = A).

WARNING! Once the multimeter is on Amps do not connect it directly across the battery and do not hit the starter button while testing for current Amps. This will cause the internal fuse in the multimeter to blow! A multimeter set on current is a very low resistance, almost a short circuit and will draw as much current as your battery will supply till something melts. Always plug the Multimeter leads back to volts when you have finished testing to avoid blowing the fuse next time you use your multimeter.

Voltage ReadingTo test for battery drain: Switch everything off on the car. Disconnect just one battery lead. For example disconnect the Positive Battery Lead. Set your Multimeter to Amps as described above. Connect the Positive Multimeter Lead to the Battery Positive terminal. Make sure the Positive Lead you removed from the battery does not touch anything grounded, like the car frame etc…. Connect the Negative Lead from the Multimeter to the Positive Lead you removed from the Battery. You should now see current drain measured in Amps. Move to the lower Amp setting on your multimeter if the current is lower than the setting on the Multimeter Low setting. Start to unplug the wires or fuses around your car and see if the current reading goes to zero. This will point you in the direction of the current thief. You can convert to Power measured in Watts by multiplying it by the Battery Voltage. Power = Volts x Amps 4.2Watts or (12Volts x 0.35Amps).

Check you meter leads. Connected to wrong input.

I’m happy to assist further over the phone at https://www.6ya.com/expert/bill_bcbb89783b08c489

take a multimeter and measure for 5 volts, red is positive
and black is negative this should be coming from a 12 volt dc power supply current should be millivolt range , the voltage dictates the heat and brightnss of the leds. if unsure goole type manufacture numbers for specs.

Check the fan capacitor.

1. Using a multimeter to check a capacitor
   Plug the red lead into the positive port of the multimeter. Plug the black lead into the negative port of the multimeter. On some multimeter's the negative port is labeled "common." The other ends of the leads have alligator clips attached to them.
   
2. Turn on power to the multimeter. Change the measurement dial to the microfarad capacitive setting.
   
3. 3 Connect the black alligator clip to the negative lead of the oil-filled capacitor. Connect the red alligator clip to the positive lead of the oil-filled capacitor. The capacitance, in microfarads, of the oil-filled capacitor is displayed on the multimeter screen. If this reading is 0 or differs from the capacitance written on the capacitor's casing by more than 5 percent, replace the oil-filled capacitor.
   
   
   

The power supply circuit could be defective. Unless you have a very expensive unit, it usually would cost more to have it repair then just purchase an used unit. If you are planning on fixing it yourself, chances are that you may not be able to find schematics or replacement parts for the unit.

Hello! Lets eliminate a few common issues...Disconnect the negative battery terminal...Leave it off for 15 - 20 minutes...Re-connect battery and observe any change in fault...Do you have a multimeter and experience using it? If so, read the voltage across the battery terminals with engine off...Should be around 12.5 - 13 volts...Start the engine...Measure again...Should read at least 1.8 volts higher...

Engine off...Set meter on X10 ohm scale...Measure from the CENTER of the negative battery post and bare metal on the chassis...Record reading...Leave lead on negative battery post and move other lead to bare metal on the engine...Record reading...In both tests reading must be under 50 ohms...

There are many Technical Service Bulletins (TSB'S) written for your vehicle...Have you had any TSB'S installed? If you purchased the vehicle used, the TSB #'s are located on the inside edge of the drivers door........Let me know what you find.................Guru..............Saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

Yes the voltmeter measures the voltage.
When you power up the computer to test the voltage on the 4 wire connectors.
Test the voltage red and balck wire should read 5 volts.
Test the voltage yellow an black wire should read 12 volts
If the burning smell is from the power supply then most likely a capacitor has blown in the switch mode power supply.
I would advise you purchase a new power supply, do not try and repair it, these mains devices can be dangerous if you don't have knowledge.

It is usually marked on the casing. +(or a red marker around the pole) is positive. If you havent removed the battery connect a bulb between one of the poles a piece of bare metal (ie engine). If the bulb lights up you're on the positive. If you have already removed the battery use a multimeter and measure voltage across the poles on the battery, if the meter gives a positive reading the red test lead is on the positve. If it gives a negative reading ie -12.35V(digital meter) the red is on negative. If you have an analogue meter(a meter using a needle) it will swing to the left when red lead is on neg.