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Hi everyone.
I belive my alternator is dead and I was wondering how I would go about checking to make sure. I don't want to go and buy a new one for 150 and find out that was not really the problem.
The other day I was driving home from my friends house at night the car started up fine but soon I noticed that the battery light was on and that the usual pulsing of hte lights that annoys me is no longer happening. I had belived previously that the pulsing was coming form the voltage regulator and I had intended to replace that. So now the pulsing was gone and witht he battery light on i was convinced that the alternator was not charging the system. The car made it home after I tured everything off in the car that used power except the headlights. By the time I got home about 30 miles away the headlights were very dim. So I belive I was just running on the battery.
If once I get my car started and the alternator is not working once the battery drains sufficiently will the car stall?
So once i go home I ordered a new voltage regulator hoping that was hte problem and not something mroe pricy.
I took out the alternator and changed the voltage regulator. While it was on my bench I tried to test it's power generating ability by hooking up a multymeter a whole slew of differnt ways to the various prongs and then spinning the pully but i never got any kind of significant voltage change out of it. This makes me belive that there is something more fundamentally wrong with the alternator than the voltage regulator. Is this a correct assuption?
I assumed that with a voltmeter, I tried both dc and ac from all differnt variations of the connecitons and never got anything more than a 1/100 of a volt change spinning it as fast as i could by hand.
Does anyone have a better way to check if it is dead?
Am I going to have to replace my alternator?
btw, the connecitons to the alternator seemed to be without flaw and hte belts seemed in good shape and tight enough but not overtight.
Thanks
Scott Dallmeyer
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1989 Volvo 240 DL 193k Miles
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I got it working, forgot to attach the ground wire oops.
Thanks again everyone.
It would be worth sticking with volvos for the rest of my life just because of the people on this site.
Scott Dallmeyer
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1989 Volvo 240 DL 193k Miles
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Great news.. glad it all turned out well!
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Michael 'Street'... one AZ '85 244DL 189K miles
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posted by
someone claiming to be John Fraser
on
Wed Jul 23 11:36 CST 2003 [ RELATED]
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You might try measuring the voltage right on the alternator output terminal just to make sure it is not a wiring problem.
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Scott,
Many good suggestions already, I would expand on the point that Don made about the alternator ground wire and also add be sure to check the little red wire.
My alternator ('86 240 ~250K mi) failed on me last December on a nasty evening in Brookline MA because the alternator ground wire finally separated from the ground lug that attaches it to the engine block. The alternator was not charging and so I eventually ran down the battery as I was running my lights and heater fan (such that it is ;)
The first indicator was my FM radio started giving me static intermittently, and my headlights grew dimmer and dimmer. As I got to my destination the engine would barely run and eventually died. I had some tools with me so I was able to check the voltage -- about 9.5 volts!!
After I charged the battery enough to get it home to work on it, I discovered the broken wire. It was very subtle... over the years it had lost some insulation, become corroded in the salt and chemical solutions from the roadway, and the wire(s) had broken.
I'm sorry this has been so long winded, but my main point is to check the ground wire to ensure that you are getting a good connection. If yours is anything like mine was, there may be oil and some chemical attacks on that connection. Try cleaning and replacing if necessary.
Also, with the small red wire, it is a common failure with 240's, and provides the energizing current to start the alternator producing current, IIRC. Check to ensure that it is making good contact and not corroded.
Hope that helps.
Good Luck!
TomD
'86 240
'93 240
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Hi again everyone.
the car is running now recharging at 13.5 volts. It seems to be working. I think changing the voltage regularor fixed it but then when I put it back on the car I forgot to reconnect the ground wire. It slipped down to where i could not see it. Ooops, but better now than later after I bought a new alternator.
Thanks Tom for reminding me to check that out.
Thank you to the rest of you for your valuable input.
I love Brickboard you guys have saved me so much money.
Scott Dallmeyer
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1989 Volvo 240 DL 193k Miles
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Hi Scott. First of all Gambit has a good point, so just take the alt. (w/ the new volt. reg. installed) to get it tested. They ususally test them free of charge at the Auto Zone, Checkers, "auto parts store". You had a question.. "If once I get my car started and the alternator is not working once the battery drains sufficiently will the car stall?"... yes it will. I experienced this myself on the freeway. While your at the auto parts store to get the alt. tested, you might as well get the battery tested. It may be a 7 year old battery (like the one I had in my Volvo). Not to mention my Voltage reg. was worn out. The battery might not even be holding a charge. So, I'd concentrate on the volt. reg. and battery. I went through this dilemma, so I hope this is the appropriate advice!
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Michael 'Street'... one AZ '85 244DL 189K miles
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Put a digital voltmeter (or a good analog meter) across the battery.
A charged battery, engine off, should read about 12.5-13.0 volts.
Engine running, charging system working, should read from 13.5 to about 14.5 volts, depending on temperature, state of battery charge, other accesories loading the elec system, etc.
Common problems with the alternator include worn brushes, failed voltage regulator (brushes and VR are a unit), and a broken ground at the alternator.
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Don Foster (near Cape Cod, MA)
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The batery is close to dead and is slightly under 12 volts, with the car on the voltage remains unchanged. I changed the voltage regulartor so there are also new brushed on it. The wires all look fine so I am guessing it is something more internal to the alternator such as the diodes or soemthing.
Thanks
Scott
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1989 Volvo 240 DL 193k Miles
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Charge the battery.... while you do that and it needs it anyway, haul out the alt again. Open it and find the diodes.... With no wires attached to the alt from the car set the ohm meter to XK, then prob a diode first one way then reverse the test leads... If it is a good diode it will read one way and not the other.... Do all of them....
If you find they are all good and read one way and not the other, then ask once again as test the armature gets detailed.
So far I am not convinced you have a dead Alt.....
DID you clean the copper slip rings, which the brushes run on?
With the engine off take a DC volt reading on the wires behind the ALT and again with the engine running.
I believe one is a ground so hold the volt meter probe to that, and with the red lead probe the other 2 wires... 1 should read the same as the battery even with the car off. The other one should not read with the dcar off, and 1/2 battery voltage with the car running...
What they do read is a mystery to me from here..
I am new here, and I like the way DF deals with giving the info, but I saw a need to try to add a bit more.. I hope this offends no one in any way. Mac
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Sounds as if the alternator isn't putting out.
Be very sure the ground is OK -- temporarily run another wire from the alternator case to the engine block.
Also, inspect the wires connected at the back of the alt. If the small red wire is poorly connected, the alt won't put out.
"...something more internal to the alternator such as the diodes or soemthing..."
Could be, although today's alternators tend to be quite robust.
Removing the alt for a bench test is a good back-up move. It does require a bit of work (and the risk of breaking something else).
Be sure to disconnect the battery ground cable before you tackle the alternator.
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Don Foster (near Cape Cod, MA)
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If you did your tests with a generator or a dynamo, it would work but, an alternator has to have some power going into the field coils to alter the magnetic feilds back and forth before it will produce power. (Hence the name.) So, to test your regulator repair, you are going to have to put it back on the car or take it to a parts place where they have a tester to test it.
Whilst you have the beastie off the motor, you may as well check the brushes too as they may well be your prolbem as well.
Gambit...
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