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Alternator or Starter Motor?

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Obtong

Obtong

Jedi Hopeful
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Alternator or Starter Motor Trouble?

The weather was good this evening so I drove my 74 MGB on an errand. On the way back the engine felt as if it was losing power. The car stalled the then it wouldn’t start again. I could hear the engine trying to crank over when I turned the ignition. Pretty soon that stopped, and all I could hear was rapid clicking (much faster than the fuel pump clicking).

A young lady driving by in her ‘64 Mustang offered to help. She turned off the head lights and told me she was going to “pop” the clutch while I pushed. The car started! I thanked her, jumped into the driver’s seat and got home as fast as I could.

I made my way home but then car would only start intermittently. I checked the battery with one of those alternator/battery testers. It showed no voltage for the alternator. The car voltage gauge was not in the “charge” area. The battery read 11 volts. While I was at it, I cleaned up the battery posts.

I sprayed the alternator with electric cleaner and returned 30 mins later to try again. The car started. This time the car’s voltage gauge registered around 12/13 (not steady) volts in the charge area, and my alternator tester showed a “low” reading of 13.5 volts.

About half an hour later I tried the car again, and it wouldn’t start. (Same symptoms as the first paragraph.) After spraying the alternator again (and waiting) the car started, a little rough to begin with, but it started.

So, is my problem with the alternator, or should I be looking elsewhere to solve this problem, such as the starter motor?

Thanks for your help

Obtong
 
I'd wonder how old the battery is too, and the conditions of the ground straps and connectors/terminals on the starter and alternator. The symptoms do sounds like a draining battery or bad connection somewhere (which could obviously be the alternator still).
 
First thing I would do, is check the battery while the engine is turned off, should be about 12.5 volts, 2nd thing, fire it up and check it running, should be around 14.5 as Chuck said. If that is all well it is either your starter relay, or more likely a dead starter!! A dead starter will very seldom start when it is hot!! GOOD LUCK!!!
 
OK. I checked the battery with the engine off this morning and it registered aboout 11.5 volts. The car started fine, and with the engine running the voltage reading was at 14 volts.

With all lights on and fan going the voltage dropped, and the car would only keep going if I gave it some gas. When the revs dropped, the car stalled.

I don't know how old the battery is, but it does look new (clean). It's a Type 26, 450CCA/65RC. From what I can tell, it appears to be well grounded.

Obtong
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Obtong:
OK. I checked the battery with the engine off this morning and it registered aboout 11.5 volts. The car started fine, and with the engine running the voltage reading was at 14 volts.

With all lights on and fan going the voltage dropped, and the car would only keep going if I gave it some gas. When the revs dropped, the car stalled.

I don't know how old the battery is, but it does look new (clean). It's a Type 26, 450CCA/65RC. From what I can tell, it appears to be well grounded.

Obtong<hr></blockquote>

Personal note: Just so you know everything you described sounds exactly like what happened to my 78B about a year ago. So I have a seeking suspicion as to what your problem is, but you should try a few simple things first.

My recommendations:
The Battery: I don’t’ want to beat a dead horse - but just because your battery looks new, doesn’t mean it is. It might have sat for way too long a time between uses or something else might be wrong with your car’s charging or electrical system that might have ruined your battery. I recommend that check your battery again. This time take it to the local auto parts store (NAPA, Checker or Cragen) and ask them to charge it for you. If something is wrong with it they will let you know. Most any auto parts store will do this service at no charge. Pardon the pun? ;-)

Ok – now that you have a “Charged Battery” (or have popped for a new one), you are ready for the next steps.

First things first – I know it’s sounds childish but check your fan belt tension and the pulleys. Once I had a cracked Alternator pulley that was at the hart of all my charging problems.

Second: Check your electrical connections. I know you have already checked you battery terminals so look at the other connections at your Starter and the Alternator. You might want to get some contact cleaner & a brush for this. Warning be careful with the contact cleaner, as it can cause damage to delicate components & paint.

Next check or measure the conductivity of your cars wires from the battery to the charging circuit as well as your grounding wires. A open or a high resistance wire could be the cause of your woes. You’ll need a multi-meter with DC Volts, & OHM functions. To confirm if a wire is good or not simply measure the voltage drop across that wire or by using the OHM function to check its resistance. Note: Voltage readings are with the ignition switch on (but don’t start the car). Resistance readings are with the ignition switch off. Results: A voltage reading should be in the almost zero volts and resistance should be almost nil as well. If your results don’t match mine - find out why and correct the problem.

Ok now that all of that is out of the way - you are ready to look at your Alternator. You have a couple of options here: You can take you Alternator to that same Auto parts store for a free check & evaluation. The only problem with this is that most auto parts store might not have the correct connectors for your MG’s Alternator. Depending on how sharp you are you can make your own adapter to take with you. Or B) you can look in the back of your Moss Catalog (or go to their web page) in the Tech Tips section on the Charging system. This clearly spells out the various tests you can perform on your own.

Now that that’s out of the way - I’m going to go out on a limb here and predict you are going to find that the problem is with your Alternator.

Good Luck!

cheers.gif


Bret

[ 02-11-2003: Message edited by: Bret ]</p>
 
Gosh! Thanks for the detailed responses!

This is what I've done since the last posting:
* I took the battery into Schucks and it checked out OK.
* I cleaned all the contacts I could find, and checked all the ground connections.
* Checked and tightened the fan belt.
* The engine started fine, and my meter showed that the alternator was charging for a while. After two minutes, the voltage dipped dramatically and the engine quickly stalled.

This weekend I'll try out some of the other tests in the Moss catalog, but I do suspect that the alternator is at fault.

BTW, my alternator has three wires going into it. The Moss catalog shows a wire labeled "AL". What is it, and is it supposed to connect to anything?

Once again, thanks folks,
Obtong
 
There may be a dead short!! Get a voltmeter, change the end to fit your cigarrete lighter and plug it in and go for a drive!! If that fails, wiggle all wires and see what happens!! I hate these kind of problems!!
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Obtong:


BTW, my alternator has three wires going into it. The Moss catalog shows a wire labeled "AL". What is it, and is it supposed to connect to anything?

Obtong<hr></blockquote>

I’m traveling right now so I don’t have my schematic with me. But I believe that this wire is the feed back to the red “Ignition” warning light in the center cluster of your dashboard.

This got me thinking and want to ask the following question: Have you noticed if this light came on at all? If not - I suspect that the lamp either disconnected or burnt out. This light will come on (sometimes) when you have problems with the charging circuit.

When I was having my Alternator problems the ignition light would come on and continue to get brighter and brighter as the charging system degraded.

hammer.gif


Bret
 
My ignition light now only *sometimes* comes on when turning the ignition. When the car stalls the ignition light is still off. What does this mean? The voltage reading drops to about 12v (no charge state) after only a couple of minutes with the engine running. It is then running on battery only.

(My ignition light used to turn on every time I switched on the ignition. After operating the starter it used to turn off.)

Bret, you said that when you were having Alternator problems the ignition light would come on and continue to get brighter and brighter as the charging system degraded. Mine is *not* doing that.

Gary, what am I looking for in the voltmeter reading in the cigarette lighter?

Thanks for all you help. I am learning lots.

Obtong
 
With a voltmeter in the cigarette liter, it will tell yuou exactly what your charging system is doing!! It will tell you wat state of charge your battery is doing, and what your alternator is putting out!! When your car is running, it should read 14.4 volts, when sitting not runnig, it should read about 12.5 volts!!
grin.gif
 
That's a good idea, Gary. Right now I have the battery cover off. I guess it would be difficult to drive and check the voltages that way! The cigarette lighter is the way to go.

BTW, I grounded the yellow/brown wire on the alternator and the ignition light came on. So...at least I know the bulb works!

Obtong.
 
I believe the red light must light up or the alternator will not charge at all. Most cars you own are this way. The light circuit acts as an exciter that gets the juices flowing in the alt.
Something else to check, take the meter out again and put in on the AC voltage scale. Now read what your alt. puts out when touching red to the alt. post, and black to the alt. housing. More than .5 volts(i think i'm being generous, i can get specific if you need) and the rectifier is going bad. That puts too much AC current to the battery, and it dies a slow and painfull death. Besides, if the alt. puts out AC voltage, DC it isn't.
With the car dying on you, I doubt you have a starting problem unless it is a separate issue altogether. Once the voltage goes below a threshold, the ignition or fuel pump doesn't have enough juice to run.
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Obtong:
My ignition light now only *sometimes* comes on when turning the ignition. When the car stalls the ignition light is still off. What does this mean? The voltage reading drops to about 12v (no charge state) after only a couple of minutes with the engine running. It is then running on battery only.

(My ignition light used to turn on every time I switched on the ignition. After operating the starter it used to turn off.)

Bret, you said that when you were having Alternator problems the ignition light would come on and continue to get brighter and brighter as the charging system degraded. Mine is *not* doing that.

Gary, what am I looking for in the voltmeter reading in the cigarette lighter?

Thanks for all you help. I am learning lots.

Obtong<hr></blockquote>

Sorry allow me to clarify a little: When I said that the ignition light got brighter & brighter – I meant to say that when I would be driving along the light would start out glowing at first and gradually increase in intensity until it was fully illuminated. When it’s on all the time you are basically running on battery power.

Here is some more info directly from the MGB Handbook. “The Ignition light serves the dual purpose of reminding the driver to switch off the ignition and to being a no-charge indicator.”

This means that under normal circumstances the Ignition light should illuminate when you first start your car and then turn off as the charging circuit kicks in. After that if the light should turn on after that then for some reason your charging circuit isn’t working – in-other-words “not charging:. Also – the ignition light should go out once the engine stops.

In my case I first saw the ignition light turn on after a day of prolonged driving. Moreover if for whatever reason I shut-off the car I couldn’t restart with-out a jump start. This is what first caused me to think that my battery was at fault. Taking it down to the local auto parts store for a test & charge. This confirmed my initial thought that indeed my battery was dead. Purchasing a new battery I installed it in my B and was filled with pride at having fixed the problem so easily. That pride was soon gone - a few days later when that battery too gave out – requiring re-charging. That’s when I started to pay attention to the ignition “idiot light” in the center of my dashboard.

In a nut shell – I was only getting a charge for the first 20 or 30 seconds after starting my car. Not unlike what you described above. Anyway after that I was running on battery power and the ignition light is the first indication that something is wrong.

Anyway it sounds like you are on the right track. Stick with the Moss troubleshooting and I think you’ll get at the hart of things soon.

My money is still on the Alternator.

cheers.gif


Bret
 
The Bosh Conversion sounds like a whole new topic in itself! How about it then, Gary?

I ordered a new alternator from Moss and it should get here in a week. As soon as I get the time I'll put it in and let you know how it goes.

Obtong.
 
With a one week wait for my new alternator to arrive I have been tinkering around my MGB, making a mental list of what needs to be worked on.

I have noticed that a relay (marked 6 RA) has some rust on the back. One of the wires connected to it is actually connected to the alternator. (Thick, brown. I checked with my meter.)

Could a faulty relay give me the same (intermitent) symptoms I've been having? (A relay only costs $10.)

Eager to learn,
Obtong
 
I don't see that relay in the wiring diagram but it's early and I haven't had my coffee. But no the relay wouldn't keep it from charging if it was defective
 
Chuck, could it be item 174 (Pg. 196, Fig 10.31 of the Haynes manual) that is pictured about one inch below the alternator?

On my 1974 MGB, the 6RA relay is on the right side of the engine compartmant right next to the fuse box.

I'm now going for my coffee too...

Obtong

[ 02-19-2003: Message edited by: Obtong ]</p>
 
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