Hi yet again I have another question on my alternator which I think I have repaired but maybe too well.
here is a brief story so far.

just put my 87gt back on the road - noticed for the first time that the voltage light on my guages did not come on - was advised to ground 1 of the wires that goes to the alternator to check it wasnt the wiring - which is wasnt.

took the alternator apart and found the brush housing destroyed and the brushes well worn.

managed to get a new housing and brushes - I then with a bit of sand paper cleaned all the contact areas on the regulator the brush housing and the 2 copper rings on the alternator shaft.

put it back into the car and connected it up still no volt light - then for the love of god the obvious hit me when the engine was out of the car last year I powder coated the brackest etc and painted the engine as you do (and I did follow $RICH$ advice about adding extra ground straps) - so I put the keys in the ignition and turned the ignition (engine was not running) to open the circuit placed a piece of wire on the top bolt of the alternator and a suitable ground and hey presto the volt light came on.

so I made up a ground wire for the top bolt of the alternator and the bracket which holds the dog bone in place.
then started the car.

this is where it gets nervous the guage reads between 16 and 17 volts when the engine is running which then stablises to around 16 volts which the drops to about 14 volts when the lights the heater are switched on.

On the guages after 17 volts it shows a red zone and then 18.

IS it ok to run at 16 volts or is there anything i should do and is there risk of blowing up the battery, fires or damage to the ecu and wiring
the alternator in question is a 94 amp

any advice at this stage is more than welcomed

jon m

The ECM and pretty much all of the electrical components of the car itself can run on 16v no problem - EXECPT for the battery. That much voltage will cook it.

Measure the voltage at the alternator - use the large terminal for + and the alternator case as ground. If the voltage at the alternator is good, but the voltage at the battery - using the + and the - of the battery are bad, then look for inperfect electrical connections.

87-88 alternators will put out higher voltage when first started. It is how they are programmed. But if you are in the 16v range after it has ran for a bit, then you are in trouble.

first thing i would check is if it really is putting that much out. the fiero gauges are not that accurate. mine says it puts out 16 but when checked with a muti-meter of quality, it really is only14.5 volts. 16 is alittle high. i think that the ecm will turn the check engine light on if the voltage it sees is too high, i might be wrong though on that.


phonedawg beat me too it. still check the voltage it is really putting out to be sure

[This message has been edited by dudewithoutfiero (edited 05-18-2012).]

thank you for the advice - I will test out tommorow
Please could you tell me what the 2 electrical connectors which are attached to the voltage regulator do other than light up the volt light?

thanks again
jon

[This message has been edited by jon m (edited 05-18-2012).]

i think it is also the sense wire. it tells the regulator what the voltage is. i could be wrong though.

Having looked in the archives at high voltage etc and asked google everything points to a bad voltage regulator in the alternator.

so I have decided in the morning I will pull the alternator and change the regulator out (i have 2 new ones on the shelf) to avoid frying the battery etc. and go from there?

thanks again for the help

jon

Don’t jump to a bad regulator yet. As said before you first need to see what the voltage actually is. First, check the voltage at the battery and then the alternator with the engine running. It should be 14.5VDC (+/- .2VDC) with no more than .5VDC difference (no load). If there is more of a difference than that, look for a bad connection between the alternator and the battery. Next, do this:
• Key on, engine off, checking the voltage with a multi-meter:
o On the alternator check:

 Main power connection (large red wire) = batter voltage at all times
• Gets power from fusible link E

 Sense wire (small red wire in the two wire connector) = battery voltage at all times
• Gets power from main power connection (from a splice near the connector)

 Output voltage (for light and gauge)(brown wire in the two wire connector) = a little less than battery voltage
• Comes from Gauge fuse through charge light and charging gauge

Given what you’ve said, it’s either going to be a bad regulator (most likely), the sense wire isn’t getting battery voltage or a bad connection between the battery and the alternator.

Hi firejo24 the curiosity got me this morning before i saw your post this is what i did

with the engine running this is what I found
the red main wire at the alt was pushing out between 14.8 to 15.3
the battery read was14.8
the guage pod read 17
I then removed the alt from the car and put in a new regulator and put back into the car - the readings were as follows with the engine running
alt was pushing 14.9 to 15.1
the battery read 14.8
the pod guage read 17 and just over
basically similar readings from either regulator.

I will now check with the engine off but with "key in" readings and keep you posted but I am thinking as this has never happened before extra ground straps were put in especially the one from the alternator this is what has caused the higher reading on the pod guage.

btw I have learned alot over the last couple of days i.e how to do a basic repair on alternators and enjoyed gaining some knowledge

jon

[This message has been edited by jon m (edited 05-19-2012).]

14.9 is a touch high but I think you’re OK. The slightly high could be an old battery (they sometimes will force an alternator to run a little high). What you have found for sure is that the gauge is reading high which isn’t a surprise at all. Just keep an eye on it and next time you go for a long drive see if the battery is getting hot (and smells like sulfur) but I think you’re in good shape.

thank you for your advice there, the battery is about 6months old.
it does make me a little nervous as when the car has been running previously ( a few years ago without extra ground straps ) the volt guage was fine however that was with an old battery.

my only conclusion as I have said before is the ground strap that i added from the alternator top bolt to a good ground in this case the dog bone bracket has made a dramatic change on the volt meter and also aided the charging of the battery

maybe the readings are a tad high with a new regulator and it may need to wear in a little

thanks again
jon

i personally do not trust the gauges when something goes wrong i ALWAYS check the real readings somehow. if the multi-meter you have is a good quality one then trust it not the gauge. My gauge in my car shows about 16-17 volts and the actual is 14.6 at the alternator and 14.4 at the battery. now if it reads more then i will check just to make sure.

the multi meter i have is a digital one of a pretty good quality.

now as I have said earlier the pod guage was not that bad readings before i put the ground straps on however since then the reading difference between the multi meter and the guage in the car is; the guage in the car is approx 2 volts more which is why i think it is the ground straps which are working properly as opposed to when they were not fitted. when a post by $RICH$ about extra ground straps - everyone commented on the difference it made and everything worked better

that said with the tempreture being a little colder in the u.k as opposed to the u.s the inital output from the alternator is a little higher.

jon

[This message has been edited by jon m (edited 05-20-2012).]

well I have ran the car and still found the voltage output to be around 14.9 and everything seems fine
the volt guage in the car does drop down after when the engine bay has warmed up a little.

but i found this on the internet which other forum users may find helpful with diagnosing there alternator

http://www.aa1car.com/library/charging_checks.htm

if you scroll down to alternator charging voltage it does state that different conditions will vary the output voltage.

jon m

The extra grounds don't cause the gauge to read higher. Insufficient ground to the instrument cluster is the most common cause of incorrect gauge readings. Delco regulators are generally set to do 13.8 v. output, and the temperature will reduce the voltage. Aftermarket regulators always have higher set voltages.