Bad Alternator?

[Josh40996]

Hello.

For the past couple day, when I start the engine on my Renault Clio MK2, just after ignition there is a rough/horse groan that comes from the same area as the alternator.

Last night, I tried to start it up and it just kept jerking forward but wouldn't start. I tried to start it again and it jerked. I tried it 2 minutes later and it just clicked, I waited again and all that happened the next time was that all the lights was flickering. I measured the voltage coming from the battery and I was getting 11.5v. I tried using a jumper to get it started, it went back to clicking but still wouldn't start. So I put the jumper on charge overnight.

This morning, I put on the jumper and the engine started immediately. I left it running for a while and tried to start without the jumper. It worked. I tested the voltage whilst not running, running and running under load.

Off: 12.2v
Running: 14.24v
Under load: 12.88v

If anyone would be able to help figure out the problem, that'd be awesome.

[shorod]

It sounds like for the most part the alternator is working, hence the 14.24VDC measurement with the engine running. What did you do to load the charging system for your "Under load" measurement, and please confirm the engine was running.

My guess is your alternator is working but your battery is shot. How old is your battery? What year is your Clio? Do you know if your Clio has a "smart" charging system? Some of the newer cars use an algorithm to only provide as much output from the alternator as needed to keep the battery charged and the accessories powered, which could explain the 12.88V under load.

At a minimum, I'd say you need a new battery. After replacing the battery, perform your checks again, and see if there is an appreciable load on the battery when the engine is off. You may need a DC clamp on current probe for this and you may need to let the car sit for about 45 minutes after closing the last door in order for the charging system to be in a resting state to get an accurate reading of load. Generally the acceptable load would be around 700 mA or less, but you should confirm the spec for your Clio.

-Rod

[Josh40996]

I just did another load test (full beam lights, heater, recirculating system, and radio). The voltage dropped to 11.4v whilst the engine was running at idle. Bump up the revs to 2000 and I get just over 12v.

The clio is from 2001 and I do not know how old the battery is, I haven't had the car for long.

[shorod]

It does sound like the alternator is struggling to keep up with the demand placed on it, or you have a REALLY bad battery that is drawing a bunch from the alternator. My suggestion would be to start with a new battery, but budget to also replace the alternator.

Here in the US most of the chain auto parts stores provide a free testing service of the charging system. The trick is you have to get the car or the parts to the parts store.

-Rod

[shorod]

It does sound like the alternator is struggling to keep up with the demand placed on it, or you have a REALLY bad battery that is drawing a bunch from the alternator. My suggestion would be to start with a new battery, but budget to also replace the alternator.

Here in the US most of the chain auto parts stores provide a free testing service of the charging system. The trick is you have to get the car or the parts to the parts store. Maybe the parts stores in your area offer a similar service.

-Rod

[Jensen91]

Maybe there is a problem in the passage of current from the battery..You might need to clean up the terminals of the battery and start the engine again..Hope that helps!