Jump to content

Alternator dead?

Recommended Posts

So been trying to figure out whats goin on.


Car running and when the brakes are applied or head lights are on the check batter light comes on and my drivers footwell fuse box starts rapid fire clicking.


I had a look at the wires coming from the alternator and they look good.


Checked the voltage over the battery terminals and got 12V....is it supposed to be 13-14?


Is my Alternator dead>?

Link to post
Share on other sites

Does your car just die randomly whilst driving and won't crank over?

Because that's a dead alternator.


Whilst the car in running you should see 13V-14V at your battery terminals, or even a touch higher.

So if the car is running just fine, and not dying, but you're not getting that correct voltage at your battery I'd hazard a guess at the voltage regulation / control module on the alternator.


Munts or Oneten can nail this probably.

Link to post
Share on other sites

Its a brand new battery....but I have been checking it and its been a constant 12V so i think you may be right about the regulator....


Was not getting more than 12V over the battery terminal

Edited by Byah!
Link to post
Share on other sites

While running check the voltage at the alternator.


If you have aligator clips and a multimeter I'd leave it on for a bit and monitor the charge rate while switching on high beams, blower motor and just see what changes you have in charge.


12v is really low. For an s13 I expect 13.8v at the battery while running with no.loads and about 13.5 with loads (that's what I've seen on s13's.


Make sure you give it a rev before reading the voltage as I find the old alternators sometimes need to be 'excited' before charging, hence the whole dim dash lights when you first start start the car at night then it all gets brighter after a rev.


Also check your big alt fuse, may look in tact but not contacting properly, I've seen a few cars like that with main fuses that are broken but look in tact with a quick visual check.


If you have a decent and constant charge rate at the alternator check for volt drop to the battery. Put your multimeter on V and one lead on the battery positive and one lead on the alternator B+. That will show you what voltage your losing through that wire, you'd be expecting 0 or close to it, if your losing voltage through there then there's resistance in the wire and that'd explain the low voltage at the battery.


Post back with results.


Jarred is on the money with the reg being faulty, it does happen.

Link to post
Share on other sites

Thanks for the tips guys.


Checked output at Alternator and came back as 12V


Ended up getting an s14 Alternator from KYP and fitted it. (needed a few small modifications to grounding point)


After install the voltage over the battery was Just under 14V so definitely a change.


I checked for battery draw when the car is off and got 0.40mA


Drove the car for half the day yesterday and seemed good. Parked up now till Friday night so when I get back to Perth, hopefully she starts.


Thanks for all the help guys!!!

  • Like 1
Link to post
Share on other sites

the position of the plug and ground cable are reversed, but that's not the main issue as the cables off the wiring harness are long enough.


The grounding thread on the s14 unit is thicker than the "eye hoop" of the wire on the s13 and comes out at a 90 degree angle.


You can however pop off the plastic cover and then undo the 90 degree attachment on the s14 unit to reveal the thinner grounding thread like in the s13....but then you are missing the plastic insulator which I thought may be needed.


So ended up finding a scrap piece of plastic and cut it down/drilled it out to size to make my own insulator. Apart from that it all fit up!

  • Like 1
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...