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Happy new year all!
I just picked up a used '93 240. Nice car, but not without a few problems . . . .
One of those is the charging system. Symptoms: Battery goes flat/not charging, and not all the warning lights come on with key "on" and engine not running. When engine is running, some of the lights--including battery/charging light--flicker faintly.
I've done a number of checks:
With key on/engine off, I checked for continuity between alternator terminal 61 on the alternator and ground; reading is ~20 ohms. (should be ~ 0 between 61 and ground, correct?)
With key on/engine off, I grounded the wire from the charge/battery warning lamp to alt#61--all warning lamps, including the battery/charging system warning light--came on bright and steady.
Checked for good ground between blue wire at back of alternator to battery negative terminal, good continuity, no resistance (>0.1 ohm).
Pole-to-pole battery voltage with engine off = 12.4 volts
Pole-to-pole battery voltage with engine running = 11.8 volts
So . . . is the alternator dead (diode/s?), or is this a problem that could be solved with new brush pack/regulator?
Any insights/BTDTs/additional checks/considerations would be GREATLY appreciated!
Thanks in advance!
Steve A-
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OK, thought I'd report back . . .
The alternator's brushes were "slap worn out" as wife.gov would say. I put in a new voltage regulator/brush assembly; alternator output is 80+ amps at 13.8 volts. All of the warning lamps now work correctly and car starts like a champ.
Alls well that ends well.
Thanks for all of the advice!
Steve A-
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Good to hear! Take good care of that battery during down times!
Phil
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Yeah, I charged the battery the day before reinstalling the alternator . . . 730 CCA if I remember.
Now on to the rest of the car . . . trying to make a silk purse.
Actually, it's turning out to be a pretty nice car. Installed euro headlamps and a pair of NOS Cibie foglights yesterday--looks absolutely bright-eyed now! Always good when wife.gov likes the new $1000 car :)
Thanks again for the good thoughts on the battery!
Steve A-
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Hi Anderssj,
The faint light flickering is what I had on my '88. I had a volt regulator laying around so I pulled the old one out and the brushes was tiny. The "new" old one I put in solved that problem.
Joakim
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Thanks! I'll be going through the garage this PM to see if I have a brush/regulator assembly (or maybe a whole alternator) already on-hand. :)
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Hi!
Just catching up to the postings.
The part about the battery showing 12.4 volts without the engine running is not very good.
It helps explain the 11.8 reading with the engine running. I bet the fuel management system did not like it one bit as this can contribute to poor performance.
The battery needs a good long trickle charge to put your readings in order with a good alternator setup that I see you are looking for in your garage.
12.4 means to me that battery is run down or is getting long in the tooth, per say, age wise. Not a good habit to operate a car under this time of year.
Give it a good charge and do not expect the alternator's system to bring it all the way back up to a good longer life if you don't!
FYI,
Car batteries are not deep cycle built. Meaning they are not to stay in a "low charge state" over long periods of time.
They do not have the extra depth, below the plates, for the sulphating debri to collect that eventually shorts the cells more quickly on regular car batteries. Deep cycle batteries are made more robust to take the temperature swings of high discharge or repetitive charging cycles too.
In most cases, a deep cycle battery is a waste of money unless you depend on auxiliary equipment to operate during off cycles of power plant support systems.
Driving a car regularly, is a must, for so many reasons to numerous to name above and beyond batteries but batteries are the first to suffer, very quietly!
GAS ranks number two as it just looses its "fizzle" over a longer time interval.
(-:)
Phil
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Thanks Phil,
Understand about the battery's state of charge. I've already recharged the battery, but with 12" of new snow on the ground, the battery is on the workbench until I can get back under the car and R/R the alternator.
best regards,
Steve A-
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"Pole-to-pole battery voltage with engine running = 11.8 volts"
Do the volts go up if you increase the revs? All of the comments about brushes, diodes and slip ring are of course relevant, but an answer to that would be good.
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Steve,
Nice diagnostics. That #61 terminal should be about what you see and not zero ohms to ground, normally, I think. I've never measured with a multimeter, so in a few minutes I'll check a spare on the shelf and come back to this thread with any change in thinking. What you report seems to me plenty "ground" to effect the lamp test.
Edit: I checked two alternators. 68 and 70 ohms respectively, regardless of probe polarity. Both have Bosch regulators, which have the 68 ohm resistor.
I notice you proved the wiring to the alternator exciter OK by seeing the lamps full brightness with key on and the wire taken directly to ground. How do the lamps look when you put the wire back on the D+ (#61) terminal?
My next step would be to pull the brush pack and check out the brushes and slip rings, if I felt confident the blue wire terminals were solid and the D+ wire proved OK as you did. I'd get a good look with flashlight and mirror at the slip rings. These alternators are coming of the age where slip rings can be worn beyond service, so if the brushes seem to last fewer miles than they did, consider the surface inside. If you take the belts loose, feel for play in the bearing while you're there.
--
Art Benstein near Baltimore
I find it ironic that the colors red, white, and blue stand for freedom, until they're flashing behind you.
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Hi Art,
Thanks for the quick reply!
With wire back on the D+ (61) terminal with key on, engine off, there are no warning lights for bulb failure, brake failure, or battery charging system. If I release the parking brake, that light also goes out. All these symptoms check with my wiring diagram for the instrument cluster.
With engine running, battery/charging warning light flickers dimly at idle, and it appears that there is no charging at the battery (actually a little less than static voltage at battery with engine off).
Good "gouge" on the slip rings. Will check those.
FWIW, I had removed the gauge cluster to repair the speedo-odo, but had replaced all of the wires correctly as far as I know (per my notes). By the way, I double-checked with a spare 93 gauge cluster with identical results.
Oh, another thought--I also installed the "plug and play" cruise control wiring and module ("while I was in there"). Any chance that a fault in CC module or wiring could cause the problem--or just coincidence? (lots of those with these old cars!)
Thanks again!
Steve A-
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With the test results you verified it is safe to say the trouble is not related to any work in the instrument panel or interior. You've proved the exciter wire is OK and isolated the charging problem to the alternator. It is my guess you'll fix it just by renewing the brushes, but that's just a guess based on statistics. At least you know where to focus your effort.
--
Art Benstein near Baltimore
Today a man knocked on my door and asked for a small donation towards the local swimming pool, so I gave him a glass of water.
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Art,
I just saw your reference to this link in another alternator-related discussion:
http://cleanflametrap.com/speedoDiag.html
I guess the 12 inches of snow we got may be a blessing in disguise--one more thing to check (the black "L-shaped" connector at the back of the speedo) before replacing the alternator.
THANKS!
Steve A-
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Steve,
Not in your case. You've already checked out everything alternator-related in your instrument cluster. That other thread doesn't deal with an alternator that isn't charging. You verified the exciter circuit. You're just waiting for the snow to melt.
--
Art Benstein near Baltimore
Subj: How To Diaper A Baby
"Spread the diaper in the position of the diamond with you at bat. Then fold second base down to home and set the baby on the pitcher's mound. Put first base and third together, bring up home plate and pin the three together. Of course, in case of rain, you gotta call the game and start all over again." -- Jimmy Piersal, on how to diaper a baby, 1968
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Thanks for the clarification Art!
After thinking about this last night I figured that was probably the case. I guess I should have thought about it BEFORE my last post, right? :)
The good news is that the snow IS melting . . . now if I could just find a 240 or two at the local pick 'n pulls.
Thanks again,
Steve A-
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