parasitic drain i am based in the uk i have a 2015 renault scenic 1.5 [FIXED]

i have a constant drain on the car done some preliminary work have 4 amp drain with the amp clamp connected i have not done much else know what i was thinking was to a digital thermometer to identify the hot fuse as i have not got a thermal camera i know i have some work to do find the drain i thought this method might speed up diagnosis any thoughts would be appreciated ta glenn

A non contact IR gun might find the warm fuse?? I do have a thermal camera but probably wouldn't use it at this point. If you have a DMM that'll reliably measure mV DC volt drop the fuses with it to find the one with the key off draw. I've attached a pdf that explains the test.

Also since you have an amp clamp stick it around the alternator power cable to see if that is the draw.

Matt T wrote:

A non contact IR gun might find the warm fuse?? I do have a thermal camera but probably wouldn't use it at this point. If you have a DMM that'll reliably measure mV DC volt drop the fuses with it to find the one with the key off draw. I've attached a pdf that explains the test.

Also since you have an amp clamp stick it around the alternator power cable to see if that is the draw.

Hello "matt t" i dont want to hijack OP post but i just have a quick question for you

Would you consider this method of finding a parasitic draw better than checking for amps draw at battery and then pulling fuses until you find the problem?

Just wondering if it is quicker? Maybe safer? Reliable?
Thank you

So the amp clamp showed a 4 Amp draw from the battery +12V feed? If so, then at 4 Amps you could use the voltage drop test method across the fuses to see which circuit or bus active is drawing the current. If possible do not pull any fuses until you narrow down the problem to a single cause (module, bus, etc.). If you have access to the circuit feed wires after the fuses you can once again use your current clamp to see which wires are flowing current without actually disabling the circuit by pulling a fuse, which after power is reapplied would wake up a bus and hence changing its current draw state. The challenge with this kind of current draw is you have to put the vehicle on life support while you are troubleshooting. Use a vehicle power maintainer, so as to not lose power while you are troubleshooting. A maintainer is better than a battery charger in that it is voltage regulated rather than current regulated.

4 amps is a huge drain, similar to a 55w headlamp bulb on a 12v car !!

First of all have you left enough time for the systems to go to sleep, i would allow a good 20 mins before testing.

With a parasitic draw of that size I would look "first" at
Alternator
Glow Plugs on a Diesel
Heated Windows / Seats
Auxiliary / Heater

Hi thanks for the reply the fault traced to auxiliary heater relay which causing the drain replaced the relay and we have had no more problems

Jose22 wrote:

Matt T wrote:

A non contact IR gun might find the warm fuse?? I do have a thermal camera but probably wouldn't use it at this point. If you have a DMM that'll reliably measure mV DC volt drop the fuses with it to find the one with the key off draw. I've attached a pdf that explains the test.

Also since you have an amp clamp stick it around the alternator power cable to see if that is the draw.

Hello "matt t" i dont want to hijack OP post but i just have a quick question for you

Would you consider this method of finding a parasitic draw better than checking for amps draw at battery and then pulling fuses until you find the problem?

Just wondering if it is quicker? Maybe safer? Reliable?
Thank you

Pulling fuses to find a drain is just Confusing and Wrong on a modern day car with Electronics !! Pulling a fuse will interrupt power to a Module, Replacing the Fuse will "WAKE" that Module and you may have to allow 20 minutes or more for it to sleep again. You could be there all day and get nowhere !!

I always use 3 things.
1. A DVM in Series measuring AMPS - Very Precise Measurement.
2. A Scope With one channel on AMP Clamp and another on Battery Voltage. NOTE: The Amp Clamp readings will Drift with Temp and Internal Battery Condition - That is why I have the DVM there. However over a long period of time the Clamp will show Current Drain that is intermittent and not Permanent.

For example. I had a VW Golf once with a very intermittent draw. In the end I left it measuring some 48 hours and saw that a large drain took place some 5- 6 hours after shutting the car down. With that it was more luck than skill that I managed to catch it as it faltered -The drivers Heated Seat would Come on for no Reason and cause a large draw. Knowing how long after shut down and being able to look for the draw across the fuses as it faltered was the moment of glory

3 An AMP Hound to measure across Fuses. www.aeswave.com/Amp-Hound-2-Automotive-A...-Circuits-p9546.html

Another good tool I have seen is this:
www.eevblog.com/projects/ucurrent/