| Drbrown | -- 11-13-2013 @ 10:22 PM |
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Alternator on recently purchased '47 Ford seems faulty. Looks like a GM; See no markings; No exterior voltage regulator; System a 12 volt conversion. Car startes/runs okay. At idle (abt 500 RPM) headlights dim significantly and alternator does not kick into charge mode. Above idle (i.e. 2000 RPM) tests show no-load 12.88 volts and only 12.47 volts under load. Batt condition "marginal" but cranks starter at "normal" 10.25 volts. Old and newer amp guages show charging and above idle can reach 30 amps. Heavy-guage red wire from threaded stud no back side of Alt runs to newer amp guage. At top back-side of Alt is a plastic snap-in connector with 2 gray small guage wires - one loops to connect to adjacent threaded stud where red wire is - other runs to somewhere behind dash near area of original working amp guage (unclear-wiring nightmare there). Does wiring arrangement sound okay ? Should I test voltage at newer amp meter ? No gound strap btwn engine and body - could try a temporay to see if headlights brighten ? Any comments appreciated.
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| supereal | -- 11-14-2013 @ 9:07 PM |
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From your description, I assume your have a "one wire" type of alternator. Most GM alternators have a two wire plug at the top. We use one of those terminals to provide a ground to kick on the alternator instead of over revving the engine. I'm not sure why one is connected to the alternator output. In the typical one wire system, the output is simply connected to the large yellow wire that runs thru the loop on the ammeter. Someone versed on alternator conversion needs to look yours over. Thirty amps will cook your battery. The usual problem with alternator conversions is that the flathead Ford engine simply doesn't turn fast enough to operate the alternator. Modern cars run the units at about ten times crankshaft speed. We install a smaller pulley on the alternator to help turn it faster. Most who trade a good generator for an alternator are disappointed. I suspect whomever did yours tried to increase the output
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| Drbrown | -- 11-14-2013 @ 10:25 PM |
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Thanks for your thoughts. True, charging above 15 amps can do damage. Right now, my sys does the extremes of often typical dim lighting at idle vs. apparent excessive output at high RPM. It is a GM Alt with the rectangular shaped plastic two-wire clip connection on top of the Alt's back side. Today rec'd some recommended wiring corrections which I'll try. (1) Install ground wire direct to Alt body - otherwise its internal volt reg may not work (2) Re-route heavy-guage red wire connected at Alt's output direct to the Batt positive post (3) For internal volt reg, one of the two gray wire currently leads from the Alt's output to the top-clip-connection, and from there the second gray wire should continue to ign switch, which I think it does now. On my own today, I found abt 12.5v across batt term's when car off, and when car at idle Alt's was/is putting out 8v .... not much but not 0v either. Next time - what happens with above changes. Re your comment: Yes, I have seen posts abt disconnecting the existing gray-wire loop from the Alt's output term, but not seen mention about using it instead as a ground for the Alt. That would at least leave the other gray-wire for conn to ign switch .... all a different scheme than first above. This message was edited by Drbrown on 11-14-13 @ 10:49 PM
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| supereal | -- 11-15-2013 @ 6:27 AM |
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You apparently have the two wire type that requires a connection to the ignition switch to turn on the unit. The other wire is supposed to run directly to the battery. This allows the unit to sense the actual battery level, and should not be connected to the alternator output post directly. The output wire reaches the battery by putting that wire thru the ammeter. The voltage across the battery post with the engine off should be about 12.6 volts. With the engine running, it should rise no further than 14.7 volts. Checking voltage is better that trying to read the amperage. As you report only 8 volts, i would disconnect the wire on top from the output post and connect to the battery "hot" side, then check the voltage reading. As the system was heavily charging, the battery may be ruined, and substituting a new one will tell? The readings you quote could show a bad cell. At our shop, we do lots of auto electric work, and any deviation from the correct wiring usually spells trouble. I have an alternator on my '47, a six volt car, and has worked well for many years.
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| Drbrown | -- 11-15-2013 @ 11:05 PM |
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Turns out I have a 10 SI GM Alt. As you note first, with my system I would use the "one-wire" arrangement with Alt output to positive batt term via selonoid stud that side. The short loop "senser" wire on top of the Alt connects to the Alt output. The second wire on the Alt top apparently can be dormant as it was intended to connect to a glowing "indicator light" on the dash .... or I supoose it could go to ground via a resistor if needed. Going to replace batt and tear into the wiring mess. Thanks very much and I'll keep you posted. Ford '47 wiring diagram attached.
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| Drbrown | -- 11-16-2013 @ 11:07 PM |
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Need to correct myself re previous reply .... My GM/Delco 10 SI Alt is the earlier 3-wire version which in my system is wired such: First wire on top is "Sensor" and loops to adjacent Alt output; Second wire on top is so-called "warning-light" lead and it goes to ignition, as you say, to activate the Alt so it goes into a charging state, even at idle. As noted at idle I found only abt 8v at Amp Gauge and Batt. As you note, should be higher and Alt needs more "sensing" - see below .... Some extend the "sensor" wire to the same connection where the Alt output winds-up at the Batt. Thus it senses voltage level at the Batt after the voltage has dropped after being reduced by the system wiring and components. However this will make the Alt increase it's voltage output accordingly. I am going to run a temporary sensor line in this manner and see what voltages I find at various points. The caution here: 12v battery manufacturers say charge at minimum of 14.4v and DO NOT exceed 14.7v, especially if a "sealed" battery. So installing a volt meter at an appropriate point in ones system is a good idea. AMPERAGE: Original Ford Shop Manual (Pg R-14) says put system under high load (see specific's) and with an Ammeter at Amp Cutout in regulator, it should read between 31 and 33 amperes. I don't have an external regulator anymore but at least now I'm not so concerned my Amp Gauge runs up to that range at higher RPM's under high demand situations. Caution here: Newer Alternators are available in relatively high Amp outputs .... chose cautiously/install minimum needed.
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| supereal | -- 11-17-2013 @ 9:56 AM |
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The sensor wire must go all the way back to the battery where it "senses" the actual battery voltage. If you bootstrap directly to the alternator out put, it will result on either over or undercharging.
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| Drbrown | -- 11-18-2013 @ 8:33 PM |
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Agreed re boot-strapping Alt wiring. The Alt line to ignition .... since it doesn't include a dash warning light, appears to need a 4 ohm/4 watt resistor in parallel. Also, Alt pulley size may need to be reduced - its rpms may be too low for proper function at idle. Otherwise, concerned about mix of old/new wiring and elec devices behind dash board. Researching wiring, safety and electrical efficiency issues ID'd some with merit. (1) relocate high-current wires and devices into engine compartment; (2) more equally distribute high-current wiring/loads; (3) reduce high-current wiring to reduce voltage drops. Plan to (a) remove high-current loop behind original Ammeter - it becomes decorative; (b)remove the modern Ammeter; (c) subsitute that with a Voltmeter whose low-current lead goes to seloniod post shared by the Batt, Alt output and Alt "senser" line; (d) expand the newer fuse panel to eliminate the potentially dangerous/original circuit breaker; (e) install three relays in engine compartment to serve the headlights and fog lights. Remaining passenger compartment wiring and devices would generally be low-current i.e. forward relay control wiring, ignition, heater and wiper motors, OD switch, dash/interior lighting, clock and wiring to rear lights. Also, lots of ground wires everywhere. Be nice if they made a vintage-style wiring harness for such a layout .... safety and efficiency wins.
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