Sarum

The battery in my '65 Cutlass died altogether yesterday and after charging overnight is now showing 13.4 volts on my digital multimeter.
Before the battery died I did a some testing at the battery and these were the results

Engine off,ignition off, battery connected 12.26volts
Engine running,electric fan off,battery connected 12.57volts
Engine running,electric fan on,battery connected 12.00volts

The volts gauge under the dash shows 11volts with engine off,ignition on,fan off so I guess this means there is a 1.26volt drop from the battery to the gauge or the gauge isn't accurate.(Summit Racing part of a cheapie trio).
With the engine idling in drive and the wipers on the other day the wipers struggled to work and the volts gauge showed 11volts which would explain why the wipers were slow in low speed and stopped altogether at the top of the windscreen on high speed.
I want to check to see what the output from the alternator is with the engine running but the only way to do this with the car's wiring is to meter at the alternator itself.This is beacause the wire from the alternator output and the heavy gauge wire running from the battery positive to the starter motor are connected together on a battery terminal that can't be taken apart readily.
On the aftermarket alternator (chromed case and fan) there is a terminal on the rear with a reasonably heavy gauge that runs straight to the positive at the battery so I can disconnect that red wire and connect the positive of my meter on that terminal
There is also a female plastic connector that has 2 wires attached ,a yellow and a blue, both small diameter.This cable dissappears around the back of the motor so I think the best thing to do is to leave this connector as it is and attach the negative of my meter to the negative battery terminal and see what I get with the engine running.
Does this sound a safe and logical way of metering the alternators output? I would hate to melt any wires or damage anything like the alternator!
Also, what sort of voltage should I expect when testing this way?

MDchanic

Yeah, just connect the (-) meter lead to your battery ground and the (+) to the Alt. hot post.

Of the small wires, the blue (if I recall) goes to the ALT light on the dashboard, which should be on when the ignition is on but the engine isn't running (or when you ground that wire with the ignition switch on), but off at all other times, and the yellow wire is the voltage sensor and should go to the horn relay post, and show the same voltage as the battery (+) when disconnected and tested.
You should check to be sure both of these are connected properly.

You can try to measure the voltage with the wire connected and disconnected from the alternator, but (provided you've confirmed good connections already) you already know that your alternator isn't making any current, so it needs to be fixed or replaced.

All internal components of Delco alternators can be gotten cheaply and easily at US auto parts stores, but I seem to recall you're in New Zealand, so I'm not sure how easy they are to get in your case, which might make it easier to just get a new one.

- Eric

oldcutlass

With the engine running you should see at least 14ish volts with a meter at the battery. Below is a state of charge chart for your battery.

Fun71

What kind of meter do you have? I ask this because I have an ammeter wired into my charging circuit instead of a voltmeter and I have seen as much as 30 Amps charging when the battery is low.

Typical multimeters have a milliAmp current range, and some of the high end meters have a 10 Amp range. I once connected my Fluke meter between the alternator and the battery and blew the 10 Amp fuse, so be careful if you are wanting to measure the current output of your alternator.

MDchanic

+1. You can't measure charging current with a regular multimeter. You need either an inductive meter or a meter meant to mount in a car's dashboard, that reads -60—0—60+ amps.

Using both an ammeter and a volt meter to diagnose charging system problems is ideal, and can generally pinpoint the problem very quickly and with certainty, but connecting an ammeter in series is a pain in the butt, and most people don't have one anyway, so we tend to rely on the volt meter.
Personally, I have both a car ammeter with test leads on it, and a Snap-On charging system ammeter that can read starter cranking current as well as charging current, so I'm all set.

- Eric

Octania

This type alternator also generally has a test port into which you probe with say a small screwdriver, causing the output to max out at around 14 volts as I recall. Try the old internet search for this feature.

here is a good start

http://www.hotrod.com/how-to/engine/...rs-quick-test/

stellar

If you remove the alternator big wire that goes to the battery, you will have very high voltage if it is working. 16+ volts. This is not a good test. You can damage the alternator if you run it like this and it still won't tell you if the alternator is good. Test with the wire connected and connect the meter at the alternator post. Take a volt reading
. Test again at the battery and see if it is the same or close. Make sure the belt is tight.

Sarum

I was aware that you lost a lot of available energy with what seems a small voltage drop but it's good to see your table for better information.
I had tested the battery with the engine at idle but only got a slight voltage (still 12 volt) increase not the 14+volts expected.
I have since read that earlier alternators need RPM to generate power so although the alternator in my Cutlass is a chromed version (assuming not old) I guess it could be an older unit with a new chromed outer or even a newer unit that faithfully copies an older electrical design.I know now that my alternator is charging the battery but maybe not that well.

Sarum

I decided that it would be a bad idea to do test the alternator output voltage by replacing the alternator output wire to the battery with my meter as at best I would blow the meter's internal fuse and maybe kill the meter altogether as I would have still used the DC voltage dial, the common and voltage lead post.
The meter I have can test for current up to 10amps (for 15 secs) if you connect to the common and the separate current lead post and switch to current testing on the meter dial.

Sarum

You are right it was a bad idea to try and measure the aletrnator output voltage the way I proposed.I have a Digitech digital multimeter which is almost idiot proof as it is auto ranging etc.
If you look at my reply to stellar you will see that I was thinking about doing exactly what you did.- a big mistake so thanks for your warning.

rustyroger

An alternator should show around 14 volts with the engine idling. Unless the idle speed is too low, or you have oversize pulleys for some reason.
My guess is you have a bad alternator. I would have thought that getting it rebuilt shouldn't be a serious problem if you are in New Zealand, it might cost more and take a bit longer than in North America but no big deal.

Roger.

Sarum

You will see from another post reply that I decided it was a bad idea to disconnect the alternator's battery connection and connect the meter in series with the battery and the alternator's output terminal.
I have tried to find the alternator I have on the Summit Racing site but couldn't locate it.I have loaded some images - you will see that it has 3 ventilation slots in a row under the hot wire terminal and has a chromed fan blade and body.It's also not a 1 wire capable unit as far as I can figure because of the 2 wire connector under the base.
About dash lights, my car has a small GEN light that shares a small window with an OIL and TEMP light.None of these lights light up at all despite me replacing the lamps.I assumed this was because the 3 warning light circuits are now connected to a gauge pod under the dash.

Moving on I decided to go for a couple of highway runs over a couple of days to see what my car's voltage gauge would tell me at higher speeds.At start up the gauge would show 11.5 to 12.0 volts but after a 15-30 min. period at highway speeds (with the electric fan off) the gauge would show more voltage.The best the gauge showed was a little over 14 volts but at arriving back at my front gate with the fan on the gauge dropped down 11.5 to 12.5 volts.This would tend to indicate that the alternator is actually charging but I think the battery just isn't able to hold a good charge for long.Once I have sorted the water leak problem (another post!) I will see if I can get a higher voltage reading at the battery with the engine running at 2000,3000 rpm but
I also think I had better get back to trying to find a GM side bolt battery with a high CCA which is quite difficult in my neck of the woods.Thanks very much for your help.

Yellowstatue

The Alt belt seems to be loose and the adjustment bolt is at the end of it's travel. Perhaps a slightly shorter belt so that the bolt is near the centre of it's travel.

stellar

Yep. It looks like a loose belt and the chrome pulley will compound the slippage problem.

MDchanic

I did say that it was okay to disconnect that wire earlier, didn't I? That was a mistake.
Sorry.


Good catch. It actually looks WAY loose. I'd remedy that before anything else, as Stellar initially suggested.


I don't know why - it's a very standard Delco 10SI unit (with chrome plating).

This article has very clear photos to help you identify the 10SI and 12SI alternators.

And this is a very thorough article about how alternators work, with some parts suggestions.

This company can supply you with whatever parts you need to fix your alternator (providing that tightening the belt doesn't fix it), but there are many others as well. Odds are that a regulator or a rectifier is all you would need, and these are light and easy to ship, and you could keep your fancy chrome plated case.

- Eric

Sarum

Well spotted, yes the belt is at the end of it's adjustment but I didn't think it was slipping though.
I will have to go for a drive and take the belt into a parts place to get a shorter one.Cheers

MDchanic

How tight is it?

It should deflect about half an inch along its longest span if you press on it in the middle of the span with one finger pretty darned hard (but not really really hard).

- Eric

stellar

Eric, funny you should say that because that is the same thing wifey said to me last nite. Of course we got into a debate as to whether it should be one really or two reallys. On the serious side, the 1/2 inch rule is a fairly good general guide, and may be correct for his application, but on applications where the longest span varries, this rule can't be used. Some cars may have a long span of 6-8 inches and some may have a longer span of 20 inches or more. Naturally the longer the span the more the deflection will be. As an example consider a clothes line of 6 feet and one of 16 feet. It would much easier to deflect the longer line 1/2 inch than the shorter one. ( This is the logic I used in the debate with wifey and told her she should be happy with the 9/16 inch deflection when considering the length and age of the material being tested.) The method I use is to tighten the belt to the point where the pulley won't spin without the belt moving when trying to turn it by hand using the fan to turn it. So if you grab the fan and turn it and the pulley moves and the belt doesn't, then it is not tight enough. This is for alternators and not for generators as the length of the generator will cause more lateral force causing the rear bearing or bushing to fail prematurley. So on generators the belt can be a bit less tight.

MDchanic

Absolutely true; the example I would use would be A/C compressor belts - the compressor is often hung way out to the side, with only one belt turning it. Of course, if you leave the compressor belt a bit too loose, nothing bad will happen, other than the car might be a bit less cool, and you'll probably hear a chirp when the clutch pulls in, alerting you that the belt needs to be just a bit tighter.

- Eric

Sarum

I bought a new and shorter alternator belt this morning and fitted it in the Repco carpark so I could see if there is any difference on the journey home.
Oddly the voltage gauge only went up as high as 12.5volts where prior I could get up to 14volts on a similar journey.
I just noticed a post with a link to what looks like a good testing methodology so I am going to follow that lead and check things out again.

Sarum

Darn, missed this post first time around so I am going to follow the testing methodology suggested on this site.Thanks

Sarum

Hi Eric, I was looking at the Summit site because my car has a Summit 4 barrel carb and gauge cluster so I figured that the alternator may be one available from Summit.I was trying to find an alternator which had the same sort of fan pulley, three cooling slots etc so I could establish whether I had a 70 amp, 130 amp or whatever model/spec alternator installed.
I think the existing alternator has an external voltage regulator which hopefully is the first image(546) attached to this post.Correct?
While I was taking photos I took a shot (the 2nd image, 556) of a unit mounted to the inner fender which has a fairly heavy power cable running into it.I have no idea what this other unit is. Perhaps someone can advise me while we are at it?
Thanks for the links I know they will help me to come to a better understanding in regard to these alternators.

MDchanic

Okay, I've got a better idea of where the problem is: We need to start with the basics.

I would strongly recommend that you read the section of the Electrical chapter of the CSM that deals with the charging system. Since you've got an internally regulated alternator, you should also read the same CSM section in a later CSM, like '73 or '74. If you've got a technical bent, the article I posted above is pretty good, too.

First: the fan pulley and cooling slots are irrelevant - your alternator is a 10SI.
THey made a few slight variations in castings, which are not important.

Second: Chrome plated alternators are usually Chinese junk, and you do not want to buy another one (at least, I wouldn't). If you need to replace the alternator, and you must have the chrome plating, then swap the cases and use good internals.

Third: The 10SI doesn't have the internal air space to cool itself with an output over about 70 amps. There are 10SI alternators sold with 100 amp or higher outputs, but they tend to overheat and are short-lived and unreliable. If you want an alternator with an output in that range you will need a CS130.

Fourth:



The object pictured here is your horn relay, which incorporates the main power distribution post.
You have an internally regulated 10SI alternator. You do not have an external regulator.


Fifth:



This object is not an Oldsmobile part. It is a Ford starter motor relay.
Some people install these because they believe that they will make their cars start better. Sometimes they do, but in general, if they help, it's because they've served as a Band-Aid covering a problem in the electrical system.
So long as you are not having any starter problems right now, you do not need to mess with it, BUT, since it is not an original part, and is not connected by original wiring, it is always possible that someone else's having miswired it is contributing to your problems.

Read up on the charging system, so you can figure out how this thing is wired, and begin troubleshooting.

- Eric

Sarum

I soon realized that my alternator has the internal voltage regulator with the D shaped test port.Following the guide at the hotrod.com website I found
the best I could get at the battery with the engine running at approx. 2500rpm was 13.6 volts and no better when my meter was across ground and the alternator's output pole.
But when I used a small screwdriver to short out the internal tab(?) I briefly got 16.87volts as well as a noise from the alternator.
I will try this test again in the morning but it now looks like it's been a problem with the voltage regulator all along.

MDchanic

Excellent - now you have a much better idea of what could be wrong.

Regulators are about $20 for those, if I recall, and easy to find.

That saves you a lot of trouble compared to all of the stuff that's been discussed above.

- Eric

Sarum

Hi again Eric,
What's that saying about forest and trees? A bit like that I guess.Anyway I tried the "short the regulator test" again today.Tried it with the engine doing 2000-2500rpm and the meter went to over 17 volts straight away.The alternator shrieked, most likely the new belt I guess - despite it being nice an tight! I am wrapped to finally find out what the problem is and also that it is a cheap fix.I also need a new wiper switch, a floor mount dip switch and a new Derales fan controller so I will most likely order them in from the US together.To give you an idea the fan controllers are $100 on "special" over here and about $40 in the USA. Thanks also for advising what the mystery items under the hood are!Funny that the horn relay is mounted to the inner guard on the driver's side for some bizarre reason close to the Ford starter relay.The horn relay is isolated from the body on rubber mounts - I know this because I have shorted it out with a spanner when working on something else.Big spark!
The starter relay I would never have figured out so it's great to know.
Another little project I have ongoing is fitting a fairy grunty stereo amp and 2.5farad cap etc into the boot (trunk) which has turned out to be a bigger thing than originally thought.The current draw of the amp is quite high so I am really interested in knowing I have a charging system that will cope.Usually I just listen to the engine's music (windows always down) but it would be good to be able to hear something else sometimes.
Thanks again for your help and also for the links, I've learnt a bit but there's a lot more to know, in time......
Norm
Auckland
New Zealand

MDchanic

Good. So we know that the rotor, stator, brushes, and rectifier are all good.
It is normal for the alternator to make noise when under load, but if it really "shrieked," that sounds much more like a loose belt.


That's where they put them.


Well, that is a different, and a serious, question.
You need to find and add up the current draw (the current IN, not the output) of all of your amplifiers, check what the original alternator output was on your car (we can tell you if we know what options you have, other than the stereo), and add those two numbers up to find out what your alternator output will need to be.
You may find that you do, in fact, need a new alternator, and you may, in fact, need a CS130.
Of course, you can probably manage with an underpowered alternator, if you don't mind your headlights dimming and your car slowing down when you turn up the volume.
(I'm not kidding - years ago I had a '68 Delta with 100-200 watts worth of amplifiers and a 32 amp alternator. I thought I'd noticed that the headlights seemed to pulse with the beat when I played music loud, but I thought it was just my imagination. Then one day I was on the highway doing about 80, and I cranked up the music and noticed that the car felt sluggish. Turned it down, the engine felt good again. Turned it up, sluggish... When I got home, I consulted the "alternator file" (the area underneath the workbench where I've thrown starters and alternators for years), found a 65 amp unit, and swapped the 32 amp out. No more problems after that.)


You're welcome, you sheep-shearin' Kiwi!
[paraphrased from an old joke that relies upon correct rendition of both the Aussie and Kiwi accents...]

- Eric

Sarum

Hi Eric, I am trying to source a voltage regulator locally but these guys (400 miles away)
http://as-parts.co.nz/c/regulatory_do_alternatorow haven't responded to my email as yet.There is another company,(only 20 miles away) http://catalogue.aespares.co.nz/A1019S
who have told me that the regulator could be one of half dozen units and that they would have to see the alternator to get the right one.Does this sound correct?
I am thinking it may be better (while Cyclone Pam is hitting us!) to open up the alternator and check out the part myself.Any problem with doing that you can think of? Thanks again.

MDchanic

Ummmmmmm... I don't know anything about the alternator that you've got , so I really can't make any suggestions about parts for it. It could definitely be one of a number of different ones.

The alternator you linked to is a 100A 10Si, which, as I said earlier, exceeds the cooling capacity of the 10SI case.

- Eric

Sarum

OK thanks Eric.It looks like a will have to go for a drive to let the local company have a look at the alternator as you have confirmed that there are a number of voltage regulators that could be the right part for my 10si.

cjsdad

If you are going to be putting in a stereo amplifier you need to make sure all the grounds for the engine and body are in place and in good shape. You have to have as much negative current capacity as you have positive. You should have the negative battery cable tightly bolted to the engine block so the starter motor gets full battery capacity, Pos and Neg. You should also have a heavy guage negative cable either from the battery or the engine to the chassis or body of the car. A ground cable to the frame is always a good idea too. The motor mounts should have rubber insulators so that is not a good connection. The body mounts are rubber too so you have to have all the negative cables in place for the electrical system to work correctly.

Sarum

I had to wait for a new voltage regulator to be sent up from Wellington and had to order a new exciter as the the connecting piece between the diode trio and the regulator broke away while taking the alternator apart.At least I had the sense to remove the alternator from the car to work on it.So much easier that way.
After putting the alternator back in and starting the car the voltage gauge only showed 11.5 -12 volts but as soon as the car was moving the voltage shown moved up to 13.5 volts and stayed that way unless the fan was on which costs half a volt.Testing with a meter across the battery when the engine was started shows 14.6 volts, as good as it gets I think.I had read that some of these alternators/regulators need some engine RPM before they provide the goods and that's what seems to happen with my setup.So thanks to everybody for the help and advice especially to Octania for putting me on to the regulator test procedure.