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Checking Power Consumption in Car: Fuse in Meter with Attached Picture Setup Explained

olo122771jedrek 11394 22
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Why does the fuse in my multimeter blow when I connect it to check car power consumption, and how should I measure it correctly?

Your meter fuse blows because the current in the car is too high for the meter input, most likely above 10 A, especially if the ignition is on or during the initial inrush when the battery is connected [#16416886][#16416876] To measure standby draw, connect a jumper/bypass first, then insert the meter after the initial charging current has passed and remove the jumper [#16416914][#16417558] If you need to measure larger currents, do not connect the meter directly in series; use a shunt or a clamp meter instead [#16419360][#20173689] If the battery really discharges in about 20 minutes, one reply suggests checking for a stuck electric heater/control module as a possible cause [#16417837]
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  • #1 16416802
    olo122771jedrek
    Level 6  
    Posts: 15
    Rate: 4
    I have a pytanko I connect as in the attached picture and I have a fuse in the meter. Why?
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  • #2 16416876
    piotrek22101
    Level 39  
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    Do you measure on the ignition switch off? Maybe the collection is greater than 10 Amp.
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  • #3 16416881
    Strumien swiadomosci swia
    Level 43  
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    olo122771jedrek wrote:
    I have a pytanko I connect as in the attached picture and I have a fuse in the meter. Why?

    Do not turn on the ignition.
  • #4 16416886
    wtełek1
    Level 14  
    Posts: 416
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    Power consumption higher than 10A and that's why the fuse is burning :P
    The second reason may be the ignition turned on, and when you try to start with the meter it is not at all :)
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  • #5 16416914
    onepiotr
    Level 25  
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    At the moment of connecting the power supply, some components of the car are started and the momentary initial power consumption is considerable. So at the beginning of the test, connect the meter and connect the power supply, and then remove the jumper.
  • #6 16417438
    olo122771jedrek
    Level 6  
    Posts: 15
    Rate: 4
    I guess that it is out, but what is the reason the car normally fires, but aku unloads in a twenty-minute, I do not know what is the matter and how it will remove
  • #7 16417458
    Strumien swiadomosci swia
    Level 43  
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    What car.
  • #8 16417525
    piotrek22101
    Level 39  
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    How can you disconnect the alternator and check then.
  • #9 16417554
    Anonymous
    Level 1  
  • #10 16417558
    klepka-l
    Level 13  
    Posts: 59
    Help: 2
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    Checking Power Consumption in Car: Fuse in Meter with Attached Picture Setup Explained
    When connecting the meter, make a jumper (green) as in the picture, then disconnect it and then it will show you what is the power consumption at rest. Because the devices need some energy when connecting the voltage source, eg capacitors must charge, on the radio and other devices
  • #11 16417611
    olo122771jedrek
    Level 6  
    Posts: 15
    Rate: 4
    c200 2004 alternator also disconnected may be the right meter in the meter
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  • #12 16417620
    Anonymous
    Level 1  
  • #13 16417706
    olo122771jedrek
    Level 6  
    Posts: 15
    Rate: 4
    thank you all for professional advice tomorrow I will see and write with which cat greet everyone and thank you
  • #14 16417719
    Anonymous
    Level 1  
  • #15 16417837
    onepiotr
    Level 25  
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    It's a pity you did not write about this unloading at the beginning.
    This car is most likely equipped with an electric heater. If it discharges the battery in 20 minutes, nothing else will do it without making a fire in the car. The heater has its fuse under the hood. Damaged (compact) control system causes that it is at work immediately after connecting the battery. The controller is a fixed element of the heater.
    Checking Power Consumption in Car: Fuse in Meter with Attached Picture Setup Explained
  • #16 16418709
    artbi
    Level 19  
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    Hello, do not do anything yourself if you have no idea how to go about it, preferably from books if you already. :)
  • #17 16419360
    Massive O. Penetrato
    Level 11  
    Posts: 20
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    Do not connect the meter directly. Use a measuring bypass, eg this one

    https://sklep.avt.pl/bocznik-pomiarowy-100a-60mv.html

    which you include in a series of klam. And with the meter you measure the voltage drop on the shunt. You know the value of the current from Ohm's law. When the current flows 100A, the meter will give you 60 mV voltage drop on the shunt. As 100A is too much (and little sensitivity), use a smaller one.
  • #18 16496067
    onepiotr
    Level 25  
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    No vin, please. We'll see what's in the C classroom ;)
  • #19 16505702
    olo122771jedrek
    Level 6  
    Posts: 15
    Rate: 4
    WDC2030072R153738 VIN
  • #20 16507161
    onepiotr
    Level 25  
    Posts: 632
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    Preheating the air here is supposedly not here. Sometimes the heater was installed in engines, but there is no need for CDI.
    Disconnect the candles. Controllers of glow plugs fell here, only then they did not heat at all. Maybe it's another case ;)
  • #21 20173562
    kp.
    Level 11  
    Posts: 197
    Rate: 17
    Hello, I know the old thread, but I have one related question.

    And is it possible to connect with a meter instead of an unfastened negative clamp and a positive one?
    I think so, but I'd rather ask.

    Checking Power Consumption in Car: Fuse in Meter with Attached Picture Setup Explained


    I am asking because in my car, I have not seen a negative clamp yet :) it is hidden somewhere in the back.
    I will probably see it when I have to replace the battery and then I will have to disassemble it all.

    However, from the shore, I only have access to the plus one.

    This is what it looks like:

    Checking Power Consumption in Car: Fuse in Meter with Attached Picture Setup Explained
  • #22 20173665
    SlawekKedra
    Level 43  
    Posts: 16639
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    kp. wrote:
    And is it possible to connect with a meter instead of an unfastened negative clamp and a positive clamp?

    Yes, of course, you can use a plus point.
  • #23 20173689
    artaa
    Level 43  
    Posts: 15050
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    You can also use an appropriate meter for currents that flow in cars, i.e. the clamp.
    As a rule, you do not need to unfasten anything, connect, etc.
    And you can see the entire process of increasing and stabilizing the current after connecting the battery / turning the ignition switch.
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Topic summary

✨ The discussion revolves around measuring power consumption in a car using a meter connected with a fuse, as illustrated in an attached picture. Users suggest that the fuse may burn due to power consumption exceeding 10A, especially if the ignition is turned on during measurement. It is recommended to connect the meter after powering the system to avoid initial high current draw from components like capacitors. The conversation also touches on the potential issue of battery discharge, possibly caused by an electric heater or faulty control systems. Users advise using a measuring bypass for accurate current measurement and discuss the possibility of connecting the meter to the positive terminal if the negative is inaccessible.
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FAQ

TL;DR: 42 mA is the median resting draw of 200 tested vehicles [MOTOR, 2021]; "always bridge the battery first" [Elektroda, klepka-l, post #16417558] Using a jumper prevents the 10 A fuse in your multimeter from blowing during inrush. Why it matters: Mis-measuring can hide the parasitic load that drains a healthy battery in minutes.

Quick Facts

• Typical quiescent current after sleep: 20–50 mA [MOTOR, 2021] • Multimeter high-current fuse: 10 A/250 V, fast-acting, 11 A continuous [Fluke 87V Manual] • Starter inrush peaks: 300–600 A for <0.3 s [Bosch Handbook 2020] • Mercedes W203 PTC heater fuse: 70 A under-hood [Mercedes WIS] • 100 A/60 mV shunt outputs 1 mV per 1.67 A [AVT Product Sheet]

1. Why does the multimeter fuse blow when I connect it to the battery?

The high-current input of most meters is fused at 10 A. When you reconnect the battery, capacitors, relays, and control units draw a surge that can exceed 10 A for a few hundred milliseconds, instantly opening the fuse [Elektroda, piotrek22101, post #16416876]

2. What current is normal once the car is asleep?

After all modules time-out, expect 20–50 mA. Values above 80 mA indicate a drain that can empty a 60 Ah battery in two days [MOTOR, 2021].

3. How do I connect the meter without sacrificing its fuse?

Use a jumper wire to keep the circuit closed, insert the meter in parallel, then remove the jumper after 30 s. This lets inrush bypass the meter [Elektroda, klepka-l, post #16417558]

4. Can I break the positive cable instead of the negative?

Yes. Current is identical through either lead. Users chose the positive post when the ground clamp was hidden [Elektroda, SlawekKedra, post #20173665] Ensure the meter’s probes are rated for the battery voltage.

5. What is an inrush current and how long does it last?

Inrush is the brief surge when ECUs wake or capacitors charge. It typically falls below 1 A within 5 s [Bosch Handbook 2020].

7. Could the alternator cause a drain?

Yes. A shorted diode trio can draw 0.5–2 A even with ignition off [AutoZone Tech Tips]. Disconnect its B+ lead during testing, as suggested in the thread [Elektroda, piotrek22101, post #16417525]

8. My Mercedes C200 battery dies in 20 minutes—what fits that symptom?

Owners reported a failed PTC cabin heater staying on continuously; it pulls 60-70 A and empties the battery fast [Elektroda, onepiotr, post #16417837] Check the heater’s 70 A fuse and relay under the hood.

9. What edge-case drains should I check?

Damaged aftermarket alarms, stuck seat-memory modules, and keyless-go antennas can draw 200 mA for hours. One luxury hybrid logged 500 mA for 40 min after shutdown—a worst-case recorded by SAE engineers [SAE Paper 2020].

10. How do I perform a safe parasitic-draw test?

  1. Turn ignition off; wait 15 min for sleep.
  2. Bridge battery post to cable with a jumper; set meter to A range and connect in parallel.
  3. Remove jumper, watch current stabilize; record reading. This three-step method saves the fuse [Elektroda, klepka-l, post #16417558]

11. What fuse does a typical automotive multimeter use?

A ceramic, fast-acting 10 A/250 V fuse rated 11 A continuous and 30 kA breaking capacity, 10 × 38 mm size [Fluke 87V Manual].

12. When should I use a current clamp?

Use a Hall-effect clamp when you need live data while starting, or currents exceed 20 A. Clamps read without breaking the circuit and survive 400 A peaks [Elektroda, artaa, post #20173689]

13. What happens if I crank the engine with the meter inline?

The starter draws hundreds of amps; the meter fuse will blow instantly and may arc, damaging the meter and leads. "Never crank with the meter inserted" [Fluke Safety Note 2022].

14. How do I find a hidden negative terminal?

Follow the thick black cable from the battery toward the body ground or engine block. Many German cars hide it behind trim; consult the owner’s manual location diagram [Mercedes C-Class OM p. 242].

15. How do I interpret 60 mV across a 100 A/60 mV shunt?

Voltage divided by 0.6 mV per amp equals current. Example: 18 mV ÷ 0.6 mV/A = 30 A flowing.

16. Multimeter fuse still blows—what next?

Replace with the exact rating, inspect leads for shorts, and verify the meter is on the A input, not µA. "Wrong jack, blown fuse" is the top user error reported by Fluke at 28 % of warranty returns [Fluke Data 2021].
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