Faulty alternator?

Level 1 User Joined: 04 Aug 2004 Posts: 32

Lately my battery has gone flat almost everytime I try to start the car. Thought it may be because it's an old and worn out battery, but i decided to check the charging voltage from the alternator just to be sure.

I expected either a normal reading, or no reading at all, but it stated 16,5v while idling Shocked

This surely is the voltage regulator? Is this difficult to replace? Could it be anything else, if so, how to i localise whats wrong? Sad

Site Subscriber Joined: 10 Jun 2004 Posts: 2317

Posibly a dodgy rectifier, trouble is with alternators, like i've found is getting parts from them is difficult. Often easier to get a new or second hand alt.

Level 1 User Joined: 04 Aug 2004 Posts: 32

Hmm... Bugger... Dunno what ive done wrong lately, as ive been forced to replace heaps of stuff lately, and suddenly noticed that my driver-side door is beeing eaten up by corrision Sad

As im no big mechanic myself, most of this has been sorted out by the local workshop, leaving me poorer than ever Sad

Just had a look in my beloved Haynes, which could happily tell me that replacing the voltage regulator was a job suited for "competent DIY mechanic"... Looks like im out for another big expense then, no matter what this might be Sad

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

haynes, pah

exchange the 'spanner rating' for 'sticking plaster' rating or 'items broken in an uncontrollable rage' rating and it'll be closer to the truth.

Level 7 User Joined: 06 Sep 2004 Posts: 230

Do they really state its for a competent DIY mechanic?? OMG bastards they just want you to go to a dealership or local garage on forehand!

Level 1 User Joined: 04 Aug 2004 Posts: 32

Hmm.. Yeah, they sure do... Dunno what im to do really... a new regulator is bout 500NOK (Â£40), and a new replacement alternator is about 2500NOK (Â£200ish), and if i have to go to a workshop on top of that... ouch... Besides, for some odd reason my alt is rate 90A, and the replacement one are 60A, and i could reallly use those extra amperes, as ive got a rather big stereo in there, and fitting a carputer as we speak

I would have to remove the alternator before i could replace the regulator, righto?

Worried bout just replacing the regulator also, if, as huwwatkins says, there could be heaps of other crap wrong too

Level 7 User Joined: 06 Sep 2004 Posts: 230

Replacing the alt is sh*t easy. Did it on the mcdonalds parking over a week ago alt out in 25 min (first time) and in 20 minutes. Job done. The thing is you have to get the headlight out on the drivers side (english car) and you are in absolute need of key 16 else you can't get the bolt from behind the ps poulie out!

I rate it as being fairly simple not simple as you have to get that d*mn bolt out and you have to get the connector out of the alt which is a b*tch!

Level 7 User Joined: 06 Sep 2004 Posts: 230

Oh yeah and tensioning the aux belt again but just check it ain't to loose or tensioned much

Level 1 User Joined: 04 Aug 2004 Posts: 32

Well, if replacing the alt is shit easy, it couldnt be to hard to replace the regulator either?
Key 16? ps pouile?

Still need to figure out whats wrong though, lol Razz

If i can get away with 1/5 of the expense i would rather sacrifise some hours of swearing

Level 7 User Joined: 06 Sep 2004 Posts: 230

Oh d*mn lost my english to dutch cartechnical translation manual Sad

Ermm ps poulie = powersteering pump flywheel (dunno what to call it)

BTW My haynes sais it's a fairly easy job??

Edit: I found it Very Happy

"een poulie" == "a pulley" and "een steeksleutel" what i called key == "c-spanner" according to the haynes translation book thinky!

Level 1 User Joined: 04 Aug 2004 Posts: 32

hmm.. now people says that 16,5v wont kill a new battery... what do you guys think?

Because i think i may killed my present battery when it was COMPLETELY discharged for about a month. it's an old battery too...

So if i just replace that with a spankling new one, would it live happily ever after with 16,5v?

Level 7 User Joined: 06 Sep 2004 Posts: 230

Probably you better first check the voltage you get on the battery when engine idle and the voltage you have on lets say your sigarette lighter if your sigarette lighter gets more then Â±14,5V stuff is gonna die on you. If that's between 11,8V and 14,4V it's pretty much ok i think. I've been trying to find some info about what voltage you can charge a car battery with but i can't find anything usefull thus far.

Level 1 User Joined: 04 Aug 2004 Posts: 32

Well... Looks like im going to replace the alt anyway... Talked with some guy who works with alternators about this, and he said that any voltage above 14,5v (or something) would eventually kill the battery, and kill most of the electrical system too...

He did also seem pretty confident that it was the rectifier, and not the regulator which was broken, because of the high voltage... If the regulator broke, the voltage would most probably sink or dont charge at all.

Ill have a chat with renault about this, if its possible to get a new rectifier, and how much for fitting it. Also, would any R19 alt fit my F3P-engine? My alt is (as mentioned) 90A, dunno why? Thought 60A was standard with this cars

Level 7 User Joined: 06 Sep 2004 Posts: 230

It vary's a lot in holland they sold them with alts from somewhere round 60 to 120 amps. although i think 90% is close to 60A. You can fit any r19 alt even a diesel alt as long as it can supply enough power.

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

the battery may still be ok. But yes high voltage kills them.

The voltage rectifier is away ont he alt so get a new one fitted. The jobs easy enough if tight, my hands are to big to fit with the radiator in.

Standard uk alt is 70A output.

Level 1 User Joined: 04 Aug 2004 Posts: 32

Hmm... yeah... well, had it to a workshop today... they meant i was the voltage regulator... so i dunno, as u guys seem to be pretty confident its the rectifier Razz

i probably end up replacing the whole lot

Newbie Joined: 29 Mar 2005 Posts: 9

I would double check that you have 16.5 volts, if you do then it is the regulator ( the zener diode has gone) You can easily change only the regulator, however if your alternator has done a lot of miles (kms) it is not a good idea to do so as the slip rings wear, your only option is to replace the whole alternator. The power rating fitted from the factory depends on the options on the car. e.g. air con, electric windows etc. and you should replace it with at least the same power.

The way to check the output voltage is to run the engine at about 2500 rpm for a few mins and while it is running check the voltage across the battery terminals. it should be between 13.2 and 14.7 volts