Megane loses power when trying to start

villej

Well-Known Member
Joined
Jan 30, 2005
Messages
658
Location
Finland
Car(s)
'03 and '06 Renault Megane
So, my long time trusty friend Megane today decided to introduce his cousin, knows as an electrical problem, to me.

It was rainy day and... I had just been playing indoor sports and had sweated for an hour. I walk to my car, turn the power on and it greets me with the usual complimentary music. Then I try to start the engine and every light wents out and all power dissappears. I turn the power off from the key, and still all lights and power is out (interior lights should be on), eventually after few long seconds interior light come back on. Everything including the clock and radio stations have reseted, also immobilizer is on. I disable the immobiliser and try to start again, and the same thing. There is a click from some relay or start motor when I try to start, but immediately after that power dissappears again. After turning the power off from the key I'm now also greeted by some relay clicking randomly dozen times for few seconds. I then pop up the hood, fiddle little with the wires coming from battery, and try to start again. Same thing happens, without the relay clicking though. Then on about fifth or sixth try the car starts normally like nothing was ever wrong.

Now, I wonder what would cause this kind of an behavior?

I would myself suspect either the ignition switch or the battery. Or maybe corroded wires to the battery. On the other hand I don't think it's the battery, because lights weren't dim at all, and everything worked until trying to start. And then it had power to crank the motor just fine when on the fifth try the car decided to start. Also the relay clicking randomly when ignition was off and interior lights being off seemed really strange. I doubt bad battery or corroded battery wires would cause those?
 
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If you cab hear the relay clicking it's on the way out.
 
Were the battery connections tight?
 
Battery connectors were tight, but when I have time I'll check them properly for corrosion too.

I have been trying to replicate the problem today withouth success. The car starts every time, despite temperature being +5 celcius and having E60 in the tank.
 
I'm thinking whatever relay you heard is going out.
 
I'll check and keep eye to all the relays too then, thanks. :)

That said, relay for the headlights has been acting funnily during winters. When it's very cold (-20 celcius or below) it has immense lag until it heats up(I suspect it is inside the cabin). It may take few seconds for it to light up short beams after I have turned the high beams off. Maybe I should replace at least it anyway.
 
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So, the problem came back for a short time. This time the start motor just clicks, and then all power dissappears. This time I was able to measure battery voltage when cranking. It went always below 2 volts. I measured it few times and it was always the same. Then on about the fifth time the voltage stayed at 11 volts, and the car started with no problem.

So I'm thinking the battery needs replacing, but it confuses me that the voltage does only seldom drop. If battery was the culprit, shoudn't voltage drop every time? Could some sort of short in electical system cause the battery voltage to drop?
 
You either have a random power drain , a shitty battery or it's just being French.

Kidding aside, this sounds like a shitty battery to me. Replace with new and stronger item. Report back.
 
The car is working again! :) Bought a new battery, but did not have to install it after all.

When I took the old battery out, I discovered that the spot where ground wire from battery connects to chassis was corroded. I disconnected the wire and applied some sandpaper, and then put the old battery back. The car has been working well since then.
 
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