Alternator wire overheating

gnolan

Hi,

I have been having some trouble with my Clio (2000) for a good while but two separate mechanics haven't been able to diagnose the problem. It came to a head today when it broke down in the middle of the road and i called out Hibernian Breakdown Assist.

I've always thought the car idled a bit low. Recently i have been having to keep the foot slightly on the throttle at lights cos it feels like its going to cut out (which it did today). The strange thing is i never have problems starting the car in the morning, ever. It starts first time and idles at around 1000 revs. After 5 mins it idling at 500-700 revs and spitting and coughing slightly. If i am to drive for about 30 mins, stop the engine, and try to restart it, it won't happen. It needs to be left for about an hour before it will get going again. Another symptom is: if i'm idling at traffic lights and turn on my high beams, roll down the windows, that kind of thing, the revs drop for the duration.

So anyway, the Hibernian mechanic came out to the car today and took a look. Of course, by the time he came out the car was starting fine and i looked like an idiot. He cleaned some sensor and then took a look at the battery and alternator and found that the wiring from the alternator to the battery was overheating, with the comment on his report being: "high resistance in wiring from alternator to battery, voltmeter reading 1440 at alternator and 1340 at battery".

Does this sound like the culprit of all my problems? Would a small discrepancy of 100 Ohms (??) cause all these problems?

Would anyone know how much it might cost to repair and what exactly needs to be repaired (new wire from alternator to battery?)?

Thanks, sorry for the long post.

Muckie

At first guess i'd have thought an engine temperature sensor
was at fault, either that or the MAF sensor. Especially since the rev's
are so jumpy.
Maybe a diagnosic check of the car might be in order.

Fabritzo

this maybe...http://www.renaultforums.co.uk/showthread.php?t=20713

Is the air filter clean?

nmacc

gnolan wrote: »

Hi,
"high resistance in wiring from alternator to battery, voltmeter reading 1440 at alternator and 1340 at battery".

Does this sound like the culprit of all my problems? Would a small discrepancy of 100 Ohms (??) cause all these problems?

This is not a resistance of 100 Ohms, but a drop of 1 volt. 100 Ohms in that lead would indeed be a serious problem. The resistance in the lead is probably quite low, maybe in the order of 0.1 Ohms, but the current can be high & if the lead is getting hot then it definitely needs to be replaced. It's a simple fix and any decent auto electrician should be able to do it for very small money.

That said, that may not be the entire cause of your trouble. If the engine slows when you place a load on the alternator, then there is a problem with the idle stabilisation. If there was a major electrical problem that caused the wiring to draw so much current that the ECU couldn't maintain a steady idle, then your battery would probably have been toast long ago.

It is probably a sensor as stated by the other posters, but the first step is to get an auto electrician to sort out that lead and check all the earths, lest the wiring problem has resulted in confused signals to the ECU. Get that sorted first and then you can start to track down any other problems.

gnolan

Muckie wrote: »

At first guess i'd have thought an engine temperature sensor
was at fault, either that or the MAF sensor. Especially since the rev's
are so jumpy.
Maybe a diagnosic check of the car might be in order.

Well like i said, he cleaned some sensor when he arrived. Said it can be a problem in these cars. The car had a full service about 9 months ago, i don't know if that includes a "diagnostic check" or not but the mechanic couldn't find out what the problem was - took a good while looking too.

Fabritzo wrote: »

this maybe...http://www.renaultforums.co.uk/showthread.php?t=20713

Is the air filter clean?

The post on that forum sounds familiar alright, albeit without the cutting out and not restarting. I should emphasise though that the car doesn't chug loudly when idling, its like small intermittent spits. I percieve the car to be idling too low but i don't know if thats the case.

nmacc wrote: »

This is not a resistance of 100 Ohms, but a drop of 1 volt. 100 Ohms in that lead would indeed be a serious problem. The resistance in the lead is probably quite low, maybe in the order of 0.1 Ohms, but the current can be high & if the lead is getting hot then it definitely needs to be replaced. It's a simple fix and any decent auto electrician should be able to do it for very small money.

My mistake, that was an assumption on my part. Would this discrepancy of 100?? (coupled with the heated wire) account for the car cutting out after about 30 mins and not restarting?

It is probably a sensor as stated by the other posters, but the first step is to get an auto electrician to sort out that lead and check all the earths, lest the wiring problem has resulted in confused signals to the ECU. Get that sorted first and then you can start to track down any other problems.

Do you think i'd be best off going to a Renault garage to sort it? Or can you recommend anywhere in South Dublin that'd know what they're doing? Can i quote any specific sensors to ask him to check?

Thanks

SV

gnolan wrote: »

Do you think i'd be best off going to a Renault garage to sort it? Or can you recommend anywhere in South Dublin that'd know what they're doing? Can i quote any specific sensors to ask him to check?

Thanks

Do not, whatever you do, go to a Renault dealership to try get this fixed..
quite possibly the biggest rip off merchants(when it comes to servicing and parts) ever.

nmacc

SV wrote: »

Do not, whatever you do, go to a Renault dealership to try get this fixed..
quite possibly the biggest rip off merchants(when it comes to servicing and parts) ever.

That's perhaps putting it a bit strongly. Perhaps.

You may indeed need to visit a main dealer, but not yet. Like I said, the first step is to get an auto electrician to sort out the duff wiring and then see how she behaves. If she's still bad it may help to have her hooked up to an analyser. I've been out of this game for too long to be much more specific than that.

As for a good auto sparks, I'm sure there are plenty of people on the boards who can advise on reputable, reasonable one. Where are you located?

SV

nmacc wrote: »

That's perhaps putting it a bit strongly. Perhaps.

Sorry but I'm basing it off my own experiences..and it couldn't be more true!
great customer service but my god do you pay for it!