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alternator problem


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chuckt504 
Member - Posts: 18
Member spacespace
Joined: July 23, 2004
Location: United Kingdom
Posted: September 19, 2004 at 10:12 AM / IP Logged  

I have a 200 amp alternator on a 98 mustang gt.  just yesterday I got a new radio put in.  The car did not have a radio nor was the sound system working at all for weeks.  I have 2 jl 12W6v2 all jl componet speaker, a 1000/1 and a 300/4.  I have tried diffent batteries to see if it was a bad battery.  disconneted all the amps, reset the computer in the car, checked all fuses and none of this was the problem.  The problem is a low RPMs and at idle.  The voltage drops from 14.4 to 11.9.  I have 1.5 cap that has a digital read out on it.  I disconneted the cap to see if that was the problem but is wasn't.  So it has to be the alternator.  Anybody have any idea what on the alterantor could be doing this.  I have all 4 guage negative and postive wires for the battery.  The car does not seem like it is going to die but the battery light does come on.  It doesn't mater if the radio is turned on or off the voltage just drops.  I do need to replace my spark plugs badly.  Could this be doing it.  I just really need some help cause it is frustrating me.  Thanks

Charles

Alpine Guy 
Platinum - Posts: 2,478
Platinum spaceThis member has made a donation to the12volt.com. Click here for more info.spacespace
Joined: October 18, 2003
Location: Canada
Posted: September 19, 2004 at 10:47 AM / IP Logged  
What kind of alt did you get??   Sounds like the alt wasn't made to produce its power at low rpm, , basically you gota be on the red line to get the output its capable of.
2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.
Teken 
Gold - Posts: 1,492
Gold spacespace
Joined: August 04, 2002
Location: Aruba
Posted: September 19, 2004 at 10:47 AM / IP Logged  
Internal Regulator or blown diode packs.
Regards
EVIL Teken . . .
chuckt504 
Member - Posts: 18
Member spacespace
Joined: July 23, 2004
Location: United Kingdom
Posted: September 19, 2004 at 10:53 AM / IP Logged  

For internal regulator or blown diode packs is that an easy fix.  It was doing fine about three weeks ago. Like I said I got the system hooked up yesterday again I was playing it all day.

Teken 
Gold - Posts: 1,492
Gold spacespace
Joined: August 04, 2002
Location: Aruba
Posted: September 19, 2004 at 11:00 AM / IP Logged  
Both items can be replaced easily by a professional. I would however have the alternator benched first at a place that you trust.
No need to spend any hard earned money to replace the unit, when it could be something totaly none related.
From there, you have a base line to start from. I am assuming you have done some very basic load tests on the vehicles electrical charging system first?
If not, I can run through some basic things you can do on your own.
Regards
EVIL Teken . . .
chuckt504 
Member - Posts: 18
Member spacespace
Joined: July 23, 2004
Location: United Kingdom
Posted: September 19, 2004 at 11:04 AM / IP Logged  
Yes please could you give me some basic things I can do on my own.  I would greatly appreciate it.  Thank you
chuckt504 
Member - Posts: 18
Member spacespace
Joined: July 23, 2004
Location: United Kingdom
Posted: September 19, 2004 at 11:35 AM / IP Logged  
Does anyone think it could possibly be one of the wires for either terminal.  I just took a closer look at my terminals and they are not that clean.  No acid but alot of dust.  Sorry to sound stupid but alternators and batteries are not my thing, good learning experience for me though.
Teken 
Gold - Posts: 1,492
Gold spacespace
Joined: August 04, 2002
Location: Aruba
Posted: September 19, 2004 at 1:00 PM / IP Logged  
Yes, dirty contacts will increase the resistance, and thus will drop the voltage as well.
Take all the contacts leading to the battery and clean them. Ensure they are properly secured and crimped to their cables, and apply some dielectric grease compond. In a pinch you may also use some Vasalene.
LOAD TEST:
1. Start the vehicle and let it come up to normal operating temperature. You will know this when the fan comes on. If it is taking a long time to warm up, rev the engine up to 2000 rpms, and hold for a few minutes.
2. Once the vehicle is running at operating temperature. Take your meter (DMM) and measure the voltage at the battery, while all loads are off.
ie. lights, wipers, radio, etc.
You should obtain a reading of aprox. 13.4 - 14.8 , maximum, without any loads.
3. Once this is done, turn on one device and measure the voltage drop from the battery. You will notice if you turn on your headlights the voltage will drop from 14.8 volts to 13.4 volts. That is ok, you will notice in a few moments thereafter, that the voltage will come back up. This is the regulator doing its job, if the voltage does not come back up at all with this simple test.
This indicates a possible problem area.
4. To varify that the regulator is indeed working as expected. You will require a helper. You will increase the rpms from idel to 2500 rmps and hold it there.
You will at that time, ask your helper to watch the DMM for voltage drops in the electrical system. He/ she will tell you *IF* and when the voltage comes back up and how long it took to recover.
ie. You will sit in the vehicle, while holding the revs to a steady 2500 rpms. At that point one minute apart you will increase the load on the engine and its electrical system.
You will start with the lights. Then the heater with the fan on max. Then you will turn on the wipers, then the A/C. You will notice that the voltage at the batteyr will drop. But within a minute the alternators internal regulator will command the alternator to output more current.
If the voltage drop down to 12 volts at any point in time and does not recover within 1 minute. You should suspect the regulator as being faulty. This same situation can also be caused by the diode packs, or stator.
Please do the test above, and let us know.
Regards
EVIL Teken . . .
chuckt504 
Member - Posts: 18
Member spacespace
Joined: July 23, 2004
Location: United Kingdom
Posted: September 20, 2004 at 2:03 AM / IP Logged  

It is the regulator.  I did the test and and took it to the shop today and they are fixing it now.  Thank you for all your help.  I know what to do if this ever happens again.

Charles


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