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| Dim Lights Alternator Question https://slantsix.org/forum/viewtopic.php?t=12891 |
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| Author: | Todd360 [ Fri May 06, 2005 9:36 pm ] |
| Post subject: | Dim Lights Alternator Question |
Hi, Recently had the opportunity to drive my '66 Dart at night a few times. When I slow or come to a stop my lights go extremely dim and my turn signals barely blink. The only "accessory" running has been the blower motor (on low speed) for the heater-also ran without blower motor to see if headlights were any brighter-they weren't. As far as I can tell the alternator/charging system is all stock. The battery stays up to charge and is less than a year old. Engine Idle speed is up to specs with car in gear. I don't run any high powered audio equipment. All the older Chrysler products I have owned have done this to some degree but not nearly as bad as this Dart. What can I do to correct this problem? Should I go to a later model alternator with electronic voltage regulator? Or could my current setup just be showing its age and need to be rebuilt/replaced? Thanks for any suggestions and help! Todd |
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| Author: | 74SCAMP [ Fri May 06, 2005 11:33 pm ] |
| Post subject: | things to check... |
i'm definately no expert, but i had the same problem with mine. if your lucky, all you will need is a phillips and you can pull your brushes and see if they need replacing (disconnect your battery first). also, check your idle rpm and see if your too slow for the altenator to charge. if your gauge is flickering, and your rpm's are good, it's probably your brushes. |
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| Author: | SlantSixDan [ Sat May 07, 2005 6:22 am ] |
| Post subject: | |
As you've noted, slight dimming at slow idle is normal with most variants of this system, but not the severe voltage loss that you're talking about—which means that with proper diagnosis and repair, you ought to be able to get the stock system working acceptably without having to change to different kinds of components if you don't want to. The suggestion to check the brushes is always a good one, though worn brushes generally tend to show themselves by flickery charging rather than by low output at idle. The regulator and its wiring are great places to start looking for the trouble. This is one of the times when substitution of the part is a decent option for diagnosis. There are lots of different options for replacement regulators for the '60-'69 system. Before you replace the regulator, though, you may want to try running a test wire between the regulator's "FLD" terminal and the alternator's "FLD" terminal, after removing the stock wire from both of these connections. If this fixes the problem, there's high resistance between the regulator and the alternator and that wire should be permanently replaced. Also make sure any regulator you install has a good ground; sheetmetal gave iffy grounds when new and even worse when old. Run a wire between the regulator base and the alternator's handy "GRD" hole—just make sure to use a short self-tapping screw in the "GRD" hole so the screw doesn't protrude far enough into the alternator to hit the rotor. Note that some of the transistorized regulators come completely coated in black or blue epoxy. If you get one of these, it's important to scrape away the coating around the mounting hole so the regulator gets a good ground. If a new regulator and/or wires don't fix the problem, turn your attention to the alternator. An open diode will drop the alternator's output significantly but not to zero, keeping the battery charged at higher RPMs but flagging at idle. To test for this, disconnect the wire from the "FLD" terminal on the alternator. Carefully run a jumper wire from the "BAT" terminal (alternator output stud) to the alternator's "FLD" terminal — if you are working with a '70-up "dual field" alternator, you need to ground the alternator's other field terminal — and start the engine. DON'T run it much above idle speed, for you are "full fielding" the alternator, taking the regulator out of the system, and if you rev it too high, the alternator will produce enough voltage to blow bulbs and cause other damage. If the full-fielded alternator gives you normal or near-normal light brightness, blower speed, etc., then the alternator's probably more or less fine. If not, then it's in need of service. Be very careful with rebuilds. It's tempting to get the $24.99 "remanufactured" alternator from the parts store, complete with the "lifetime warranty", but if you want to do the repair just once, stay away from this indifferently-thrown-together junk. That "lifetime warranty" means you get to spend your "lifetime" swapping repeatedly-dead remanufactured parts under "warranty". Much better to take your alternator to a local auto starter-alternator rebuilder (check your yellow pages) and have it rebuilt and returned to you. The warranty may be as short as 30 days (usually 90) but you'll likely never need it. The cost may be somewhat higher, but it's worth it to get quality components and skilled work. |
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| Author: | Todd360 [ Sat May 07, 2005 8:47 am ] |
| Post subject: | |
Thanks Guys-lots of good info there-I'll try some of these tests shortly. Todd |
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| Author: | Todd360 [ Sun May 08, 2005 7:42 pm ] |
| Post subject: | |
I tried the tests Dan provided above-everything checked out except for the "full field test". Lights didn't get any brighter with the field wire off. Checked voltage coming from the alternator and it was running between 10 and 10.5 volts. That was with the motor idling at about 850 rpm. So tomorrow I'll pull the alternator off and take it to my local friendly rebuilder. Thanks again, Todd |
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| Author: | SlantSixDan [ Sun May 08, 2005 7:57 pm ] |
| Post subject: | |
Yep, you'll probably be fine once the alternator's been gone through. Unless you're planning on running lots of non-stock electrical accessories, there's no call to increase the amperage it can put out by changing the stator or rotor. The tradeoff for increased maximum total amperage is <i>less</i> low-speed charging. |
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| Author: | dank10fenny [ Thu Nov 08, 2007 9:34 pm ] |
| Post subject: | |
i thought to full feild it u throw 12v at a feild wire, or do u ground... help! |
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| Author: | SlantSixDan [ Fri Nov 09, 2007 8:39 am ] |
| Post subject: | |
Detailed, clearly-written instructions for full-fielding the alternator are already present in this thread. If you do not understand them, read them again. If you still do not understand them, it's probably best you don't attempt the test. |
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