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Renault Laguna 2 1.8 16v 2002 - Short circuit in the installation

Ferin 11724 18
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How can I find the cause of a parasitic current draw in a 2002 Renault Laguna II 1.8 16V when removing the ALIM UCH cabin fuse and two engine-compartment fuses makes the draw disappear?

First verify the current draw after the car has gone to sleep with the meter already connected; that is the correct way to test it, and 0.12 A after sleep is still too high for this car [#16761788][#16765472] The cabin fuse marked ALIM UCH is fuse 2 for the UCH computer / 10A chip-card reader, and the two under-hood fuses mentioned are fuse 18 (passenger compartment 1, 70A) and fuse 21 (electrical disconnection / passenger compartment 2, 60A) [#16761708] On similar Renaults, normal resting consumption is around 0.013 A without an alarm and typically below 0.05 A even with extra equipment, so your 0.12 A still indicates an abnormal draw [#16765472] Check the car in sleep state, preferably locked with the card rather than the key, because the draw should be measured after all modules have shut down [#16761825][#16765530] Since the current jumps when inserting the card and you also noticed intermittent loss of response from the slot, the chip-card reader/UCH area is a likely place to inspect next [#16761708][#16763152]
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  • #1 16761657
    Ferin
    Level 9  
    Posts: 22
    Rate: 4
    Hello. In my lagoon two 2002 1.8 16V I have a short circuit, it is leaking about two amps. With the help of the meter, I was able to find the cabin fuse - ALIM UCH - after removing which the leak disappears. I also checked the fuses in the engine compartment and there are two when removed, the short circuit disappears. I wanted to ask where and how to start looking for the cause of the short circuit. Adds photos with marked fuses mentioned above.

    Only the fuses in the cabin are described in the service book, will someone share a link to the description of fuses / relays in the engine compartment?
    Renault Laguna 2 1.8 16v 2002 - Short circuit in the installation
    Renault Laguna 2 1.8 16v 2002 - Short circuit in the installation
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  • #2 16761681
    moto-kord
    Level 28  
    Posts: 800
    Help: 137
    Rate: 501
    What is your power of 85 or 89 kW?
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  • #3 16761687
    Ferin
    Level 9  
    Posts: 22
    Rate: 4
    moto-kord wrote:
    What is your power of 85 or 89 kW?

    115 horses, the conversion factor shows that 85.7 kilowatts. I didn't even know they were 89. Are they very different from each other?
  • Helpful post
    #4 16761708
    moto-kord
    Level 28  
    Posts: 800
    Help: 137
    Rate: 501
    Fuse 2
    UCH computer
    10A chip card reader
    The two big ones under the hood
    Fuse 18
    Passenger compartment 1 70A
    Fuse 21
    Electrical disconnection
    Passenger compartment 2 60A
  • #5 16761716
    Ferin
    Level 9  
    Posts: 22
    Rate: 4
    So the reader is most likely causing a short circuit?
    Is my inference wrong?
    Gotta pull out and watch carefully, thanks for your help.
  • #6 16761723
    moto-kord
    Level 28  
    Posts: 800
    Help: 137
    Rate: 501
    The easiest way is to connect a diagnostic device if you have such an opportunity.
  • #7 16761725
    coperfild
    Level 35  
    Posts: 2745
    Help: 291
    Rate: 1686
    A colleague is not short-circuited, only the consumption if the fuses are whole, we do not know if he is measuring correctly, after putting the system to sleep.
  • #8 16761774
    Ferin
    Level 9  
    Posts: 22
    Rate: 4
    coperfild wrote:
    A colleague is not short-circuited, only the consumption if the fuses are whole, we do not know if he is measuring correctly, after putting the system to sleep.
    I waited about twenty minutes after removing the key, I can check again tomorrow to be sure. If so, I am asking for advice on what and how.
    I do not have an interface to connect the computer, so I will not check it.
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  • #9 16761780
    moto-kord
    Level 28  
    Posts: 800
    Help: 137
    Rate: 501
    Ferin wrote:
    I waited about twenty minutes after removing the key

    Of course the meter was plugged in and turned on?
  • #10 16761782
    Ferin
    Level 9  
    Posts: 22
    Rate: 4
    moto-kord wrote:
    Ferin wrote:
    I waited about twenty minutes after removing the key

    Of course the meter was plugged in and turned on?
    I connected the meter and turned it on only after the aforementioned time, I should connect it immediately after removing the key and check how it changes with the passage of these twenty minutes?
  • Helpful post
    #11 16761788
    moto-kord
    Level 28  
    Posts: 800
    Help: 137
    Rate: 501
    Ferin wrote:
    should I hook it up right after removing the key and check how it changes with the passage of these twenty minutes?

    That's exactly what you have to do. Everything must sleep on the connected meter.
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  • #12 16761794
    Ferin
    Level 9  
    Posts: 22
    Rate: 4
    Ahhh, I didn't know, I'll do it tomorrow and let you know the result at the beginning and after twenty minutes. Thanks.
  • #13 16761825
    coperfild
    Level 35  
    Posts: 2745
    Help: 291
    Rate: 1686
    It would be good to close the car with the central card, not the key.
    Nice meter, best regards.
  • #14 16763152
    Ferin
    Level 9  
    Posts: 22
    Rate: 4
    coperfild wrote:
    It would be good to close the car with the central card, not the key.
    I don't know what you mean, I can lock the car with a key / card or with a button from the central wheel of the handbrake lever.
    coperfild wrote:
    Nice meter, best regards.
    Thanks.

    Today I checked the power consumption again. And so, right after it was turned off with the card inserted, it was charging 3.75A.
    After removing the key, it dropped to 1.25-1.78A after a while (2 minutes approx) 1.51 and after 5-10 minutes to 0.12A.
    Is 0.12A low enough or should it be less after everything is put to sleep
    what should be dormant?

    Well, zonk, because it seems that the short circuit has opened, I am not happy about it because I think something will come back.
    I inserted the card without turning on the engine and it jumped to 3.75A, after removing it, the sequence was as above.
    Sometimes, rarely but still, it happened that I inserted the card and nothing, complete silence, I took it out and put it in
    one more time and everything came alive. Maybe the slot is damaged and sometimes it has something wrong. I have to undress it and watch it.
    Unless you have other suggestions.

    Anyway, thank you to everyone for their help and tips.
  • #15 16763373
    moto-kord
    Level 28  
    Posts: 800
    Help: 137
    Rate: 501
    Ferin wrote:
    Is 0.12A low enough

    It's good.
    Ferin wrote:
    I have to undress it and watch it.

    Do not disassemble anything. We check the consumption after sleep, no one leaves the car with the card.
  • #16 16764575
    Ferin
    Level 9  
    Posts: 22
    Rate: 4
    moto-kord wrote:
    Do not disassemble anything. We check the consumption after sleep, no one leaves the car with the card.

    I did not undress anything, left the battery connected to check if I would start today, before it was discharging.
    Well, so far it is good, although I have the impression that it will come back, rather nothing repairs itself.
  • #17 16765372
    Strumien swiadomosci swia
    Level 43  
    Posts: 27411
    Help: 1403
    Rate: 6379
    I would have seen the grommets in the door and the flap whether or not broken.
  • #18 16765472
    freebsd
    Level 42  
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    Rate: 2025
    Ferin wrote:
    Is 0.12A low enough or should it be less after everything is put to sleep
    what should be dormant?
    Too much. Without an alarm and with the company's radio, similar Renault models use, for example: 0.013 A. If I added an alarm and other radio (decent and properly installed), I would expect a consumption below 0.05 A.
  • #19 16765530
    Strumien swiadomosci swia
    Level 43  
    Posts: 27411
    Help: 1403
    Rate: 6379
    See if there is this consumption right after the clamp is established.
    I had one that, after switching the ignition on and off, the relay never turned off.
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Topic summary

✨ The discussion revolves around a short circuit issue in a 2002 Renault Laguna 2 1.8 16V, where the user identifies a current leak of approximately two amps. The user successfully locates the cabin fuse (ALIM UCH) responsible for the leak and checks fuses in the engine compartment, noting that removing certain fuses eliminates the short circuit. Participants suggest various diagnostic approaches, including using a meter to measure power consumption after the vehicle is turned off and ensuring the system is in sleep mode. The user reports fluctuating current readings, indicating potential issues with the chip card reader or other electrical components. Recommendations include checking for proper fuse descriptions, ensuring correct meter usage, and inspecting door grommets for damage.
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FAQ

TL;DR: A healthy sleeping draw on a Laguna II should settle well below 0.12 A; “Everything must sleep on the connected meter.” [Elektroda, moto-kord, post #16761788]

Why it matters: This FAQ helps Laguna II owners diagnose battery drain versus real short circuits, fast.

Quick Facts

How do I measure parasitic battery drain on a Laguna 2 correctly?

Connect your ammeter immediately after removing the card/key. Do not open doors or wake modules. Wait for sleep. As one expert notes, “Everything must sleep on the connected meter.” Record current at start and after sleep. [Elektroda, moto-kord, post #16761788]

What current draw is normal after the car falls asleep?

Target a sleeping draw near 0.013 A with the factory radio and no alarm. With an alarm or aftermarket radio, stay below about 0.05 A if installed correctly. Anything above those numbers warrants further isolation. [Elektroda, freebsd, post #16765472]

My meter shows about 3.75 A right after shutdown—normal or not?

High current immediately after shutdown can be normal while modules park. In the thread, draw started near 3.75 A, dropped to ~1.5 A within minutes, then settled near 0.12 A after 5–10 minutes. Measure trends before judging. [Elektroda, Ferin, post #16763152]

Is this a short circuit or just parasitic consumption?

If fuses are intact and current decreases as the car sleeps, you are likely seeing parasitic consumption, not a hard short. Confirm by measuring from shutdown through sleep without waking the network. [Elektroda, coperfild, post #16761725]

How long should I wait for the Laguna II to go to sleep?

Plan for several minutes. In the reported case, current stabilized near 0.12 A after about 5–10 minutes. Keep the meter connected the entire time so the network stays undisturbed while modules time out. [Elektroda, Ferin, post #16763152]

Which fuses feed the UCH and card reader in this car?

Fuse 2 supplies the UCH computer and the 10 A chip card reader. In the engine bay, check Fuse 18 (Passenger compartment 1, 70 A) and Fuse 21 (Electrical disconnection, Passenger compartment 2, 60 A). [Elektroda, moto-kord, post #16761708]

Could the card reader be causing the drain?

Yes, especially if inserting the card intermittently does nothing and a reinsert wakes the system. Those symptoms point to a flaky reader keeping modules awake. Inspect the reader and its connector carefully. [Elektroda, Ferin, post #16763152]

Do I need a diagnostic scan tool for this?

It helps. A scan tool can identify modules that fail to sleep or report faults keeping the network awake. When available, connect diagnostics during testing to speed root‑cause identification. [Elektroda, moto-kord, post #16761723]

Should I lock the car during the sleep test—card or key?

Yes. Lock the car with the central card, not the mechanical key, to replicate real conditions and allow proper sleeping behavior. Avoid opening doors until you finish measurements. [Elektroda, coperfild, post #16761825]

What immediate checks help after reconnecting the battery?

Measure current right after reattaching the terminal clamp. Some relays can stick after ignition cycles and fail to drop out. Catching that surge early speeds diagnosis and prevents a misread. [Elektroda, Strumien swiadomosci swia, post #16765530]

What wiring weak points should I inspect physically?

Check door and tailgate rubber grommets and harness sections for broken conductors. Damage there can keep control units awake or intermittently short to ground during movement. Flex the loom while watching the meter. [Elektroda, Strumien swiadomosci swia, post #16765372]

What did the OP’s car settle at after sleep, and is that okay?

It settled around 0.12 A after several minutes. One expert in the thread judged that value acceptable for that vehicle’s state. Track your own baseline and aim lower if possible. [Elektroda, moto-kord, post #16763373]

How do I isolate the drain with a 3‑step method?

  1. Connect the ammeter right after removing the card and lock the car.
  2. Wait for sleep; note stabilized current.
  3. Pull and replace fuses one at a time, watching for a significant drop. “Everything must sleep on the connected meter.” [Elektroda, moto-kord, post #16761788]

Which fuse names should I start with if ALIM UCH drops the draw?

Focus on circuits fed by the UCH and the card reader. Start at Fuse 2 for the UCH/card reader, then verify the related high‑amperage feeds under the hood noted earlier. [Elektroda, moto-kord, post #16761708]

Does engine power variant (115 hp) matter for this issue?

No. The parasitic draw process is the same. For reference, the 115 hp 1.8 16V equates to about 85.7 kW, but electrical diagnosis remains unchanged across those variants. [Elektroda, Ferin, post #16761687]

Expert tip: what single mistake skews results most?

Opening a door or connecting the meter late wakes modules and restarts timers. Always connect immediately and let the system sleep on the meter. [Elektroda, moto-kord, post #16761788]
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