T/S Alternator -
 

From reading through the discussions on troubleshooting a questionable heat soaked alternator there appears to be a few basic steps that continue to be repeated. Please chime in to add your comments and any recommendations -

1) Clean all the major Ground Points
2) Clean/Replace Battery, Jumper post and Alternator Cables
3) Clean the 14 Pin Connector Plug Pins (Razor Blade Spreads Male Term Pins Perfectly)
4) Replace Motor to Frame Ground Strap
5) Check Alt Drive Belt for Condition and Tightness

6) Test Alt Charging Light Circuit
Volt Meter Light On - Key On Engine Not Running
Volt Meter Light Off - Engine Running

7) Alt Not Charging Until RPM @ 2K
Check Voltmeter Light Wiring - Bulb and It's Parallel Resistor
Check D+ Connection @ Alternator

8) Compare Alt Output Voltage @ Battery and Jumper Post

9) Test Alt Voltage @ Idle, Then @ 2K Rpm (Headlights On- Engine Warm)

10) Alt Voltage 13-14 Volts, Loaded Head Lights On - Only When @ 2K RPM
Replace Voltage Regulator
Smaller Pulley

11) Replace Alternator

I had replaced my VR with a Huco Unit, added an insulated heat shield between the alt and engine, refreshed cooling air ducting to the alternator and installed a smaller serpintine pulley on my old Paris-Rhone 90 Amp alternator several years ago.

The most important pulley spec's were the stand off distance measured from the back of the pulley to the 1st groove, the 17mm shaft diameter and the surpintine belt surface diameter @ 48mm - my original pulley dia was 52mm.

So far, this has kept the charging system on Miss Purdy doing fine even at idle without having to replace the std 90 amp alternator with a larger unit.

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http://forums.pelicanparts.com/uploa...1500477350.JPG
http://forums.pelicanparts.com/uploa...1500477350.JPG

Michael

Voltage Accuracy -
 

After a long testing process of swapping alternators, voltage regulators, battery sizes, electrical cables, ground cleaning, 14 pin connector tests, cooling air ducting and finally a slightly smaller alt drive pulley - I seem to have the right combination to keep Miss Purdy electrically happy. My remaining complaint is that the accuracy of my dash voltmeter sucks - it can be tweaked to read (reasonably) close to alternator voltage only to deteriorate toward nothing but an aggravation within a year.

I've about worn out my dash pod taking it apart over the past 8 years while chasing this problem around. After the latest round of cleaning, I'm at the point that a digital multi-meter shows that the charging voltage at the battery and jumper post are both identical, my dash voltmeter typically reads about 13 volts while my charging voltage is actually 14.16 . I realize that this may seem to be a minor point but I want to make sure I'm not running on the battery when sitting in heavy summer traffic with the A/C on.

The solution was to permanently install a small digital gauge that monitors the jumper post/battery. I cross checked the accuracy of the new gauge several times with a Hewlett-Packard hand held multi-meter. My comfort level is much better now even if my dash voltmeter creeps down toward some erroneous 12 volt mark. My idle was set to 800 - 900 during the tests.

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Michael

sounds all good.

after reading your post i decided to check mine. stuck the multimeter on the battery all good at 12.5 (new battery). this is with engine off

started car and stuck lights on wipers on flashers etc the reading was at 13.5. now here's the part i'm worried about as soon as my ac was turned onto full pelt the meter read 13.1

SHOULD I BE WORRIED :eek:

with engine on and everything on its between 13.1 and 13.5

I haven't check the car at 2000 rpm yet only after driving for about 15 odd minutes.

and yes the instrument panel drops down to 10 ish on driving and on load

someone tell me this is normal please please please

so i was wondering about this on my car - we took a road trip (700 miles) about a month ago and i did see the dash volt gauge go below 12 at highway speeds - so i tested it today at the jump post - you can see the results below - first picture is warmed up, at idle, high beams on - second is warmed up, 2000 rpm, high beams on - you can see there is a big discrepancy - even worse was when i turned on the a/c on high..the dash gauge fell to just above 10 while the voltmeter just dropped about .25 volts - so has anyone figured out what the problem is here? - wires to gauge, those ribbon wires in pod or the gauge itself - i would like to get this fixed and will start investigating to see where the voltage drop occurs - anyone know which ribbon connection in pod is the volt gauge one? - i figure if i can find that connection and it's got the same as my voltmeter i'll know it's the gauge - oh..and big load.. mine did drop to just above 13 volts with the a/c and everything else on so i think you are ok there - or we are both messed up - and yea i know i had the + and - reversed

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http://forums.pelicanparts.com/uploa...1504035925.jpg

Dash Voltmeter - Jumper Post
 

Hey Honerboys - I had found very similar Dash Voltmeter vs Jumper Post voltages on Miss Purdy. I don't consider myself an expert but I have spent some time and effort trying to improve the reliability of my voltmeter. Naturally we not only all want the output of our alternator to maintain a charged battery and enough oomph to keep the spark plugs firing - but we want to reliably see this process while behind the wheel. There are a few 928 owner's whose Dash Voltmeter does not fall below the 12.5 - 13 volt position even while stationary with the headlights, a/c and brakes applied. But this seems to be rare.

As the needle of my dash Voltmeter began to gradually deteriorate after the 3rd trace/edge connector cleaning, it became obvious that I needed to look at another option. So - I decided to permanently connect a digital Voltmeter to the jumper post on the right hand inner fender to independently monitor the alternator output. Like my previous photos show, after once again cleaning all the major wiring connections, I mounted a new VM in a small inconspicuous plastic box that squeezed between the top and bottom lip of the storage shelf. Now even if my dash VM appears to be reading 12 volts, the digital VM by my left knee will provide the actual alternator output status.

There are several guru's on this and other 928 sites who have written extensively on how to interpret the status of the alternator output vs the battery voltage. Please correct me - but I think a new fully charged lead acid cell should be + 2.2 volts. A typical 6 cell car battery should read approximately + 13.2 statically.

Good Luck, Michael

if it ain't broke don't touch it that's what my take on this is :)

from past experience the more you touch the more goes wrong on these old cars. or should i say fix one thing and you then notice another problem

Anybody with a spare cluster, try using probes and connecting directly to the voltage gauge and see how it compares to a meter. Maybe also measure the current going through the gauge at the same time.

Sorry to jump on this thread, but it does have some relation! Took my 83, s out today, and no charge showing on the dash, put a meter on the jumper post, and across the battery, it reads 12.1 volts, and doesn't increase with any revs..

Always worked fine up until this day, I would normally suspect it was simply the alternator at fault, but is there something I should check, before ordering a replacement?!

i'm always a bit suspicious of jumping on the obvious when something goes wrong suddenly - so i wouldn't run out and get a new alternator ...yet - check your wires, grounds, connections on alternator - check voltage from heavy wire connection on alternator to engine block with engine running - that said...it could just be the alternator -

Ok, looks like the alternators toast! It's the early Paris rhone type.
There seems to be little to no replacement ones over here, but loads of the later model ones-can these be fitted, if the third threaded lug is cut off does anyone know?.. if that makes any sense?

Or any suitable replacement, that can be located in the uk[emoji1]

I recall some issue with early cars where the "exciter" circuit to the alternator goes through the bulb in the cluster or something like that, bad bulb, no charge.

As I understand it alternator is easy to rebuild or have rebuilt.

Good Grief- Now What ?
 

I had previously posted some of the troubleshooting steps taken while trying to resolve Miss Purdy's poor alternator performance over the past 8 years. This process includes - 2 Bosch alternators (both eventually failed - heat related) and then a new Paris Rhone Alternator swap, New Bosch V/R (developed low idle volt), new 14 volt Huco Volt Reg upgrade, wiring circuitry cleaned-verified good multiple times, home made custom fit alternator heat shield installed, added a digital voltmeter to monitor the jumper post voltage, new cooling air hose, installed a new alt shroud seal and finally the installation of a smaller alt overdrive pulley. With a consistent +13.9 volts at the jumper post at idle, I felt SURE that my charging system problems were all reliably behind me.

Fully expecting a trouble free road trip to Colorado, my wife and I had just filled up near Pagosa Springs on the labor day weekend when suddenly my dash voltmeter dropped to 10 volts, the red alternator low volt warning light came ON and my jumper post digital voltmeter read 11.6 volts. "Now What The !@$%#^%". Seeing my hood up, a guy walked over to ask if I needed help and luckily knew of a local auto-parts store and a hotel not too far away. I later verified that my the alternator belt, external wiring, excitation circuitry, V/R brushes and primary connections were all good - my latest Paris Rhone Alternator had definitely failed.

With a borrowed jack stand in place - this was our initial view of Colorado. Fortunately my wife has a good sense of humor and is used to my typical "self inflicted" Caaaaaatastrophes....:)

http://forums.pelicanparts.com/uploa...1505090376.jpg

It took another full day to arrive but the (1988 Camaro 2.8) 105 Amp Delco CS130 Alternator, a slightly shorter 34 inch 5 rib belt and GM pig tail I ordered came in and was installed. I had to add a small stack of washers to shift the alternator slightly FORWARD to better align the alternator pulley with the crank pulley. Of the three wires - only the "L" wire on the GM pig tail is used and spliced into the original alternator excitation blue/green wire. The Main Harness Red Output Cable connects to the Alt B+ terminal post.

After the latest grief of being stranded for several days - I now definitely regret all of the time, effort and money I wasted trying to nurse, massage and tweak the antiquated stock 928 Bosch and Paris Rhone designed alternators. In my opinion, I should have "Cut-To-The-Chase" and immediately installed a Delco alternator 8 years ago.

Once Miss Purdy was back up on her feet, my wife and I were able to do some sight seeing in Ouray, take a jeep tour through Yankee Boy Basin and Engineer Pass to visit some ghost towns, ride in an authentic stage coach and spend some time in a Silverton bed and breakfast.

Michael

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YaHoo - There's No Place Like Home
 

The Delco alternator got us safely back to Texas. Mercy - The government sure does waste a lot of tax payer's money printing up speed limit signs. We were often doing 80 - 85 on interstate and was about sucked up the intake a couple of times. :)

There were several short cuts I took during the initial installation that I needed to make more permanent:

1st - The alternator upper pivot mounting ear is not as wide as the original Bosch/Paris Rhone and the diameter of it's bolt hole is larger. Once home I cut a piece of tubing and used a vice to press in a sleeve that not only reduced the bolt hole diameter but I added a slightly larger spacer over the end of the sleeve to widen the overall width of the ear. The upper pivot point (ear) is now the correct dimensions and a nice tight fit in it's mounting bracket. The photo shows the tubing sizes I used. The smaller one had a light press fit through the upper ear but still allowed the long pivot bolt to pass through. Only a very short piece of the larger tubing was needed to slide over the protruding end of the smaller tubing to provide a snug fit between the mounting bracket.
http://forums.pelicanparts.com/uploa...1505259113.jpg

2nd I drilled out the lower ear so I could reuse the original belt adjustment setup. The width of the lower ear is also less than the original Bosch unit so again a short length of tubing is used to allow the 34 inch belt to tighten down.
http://forums.pelicanparts.com/uploa...1505259023.jpg

3rd The alternator excitation-warning light wire was soldered to the "L" wire of the pig tail for long term reliability.


The pulley that comes installed on the CS130 alternator has 6 ribs while the 928 crank pulley has 5. I found that (for my car) the best installation position for the CS130 alternator was when it was moved forward within the upper mounting bracket while the belt rides one rib back on it's pulley.
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