641 Electrical Issue

[UseFixUse]

The 12 volt conversion on my 641 has worked fine for 30 years. But now, the battery drains in a few days if I don t disconnect the negative (ground) cable. When running, the dash voltage gauge is pegged to the left (lowest reading). The battery is good. I had the alternator checked and it s good. I believe it was checked without the VR. I repaired the broken wire insulation issues in the picture. It didn t make a difference. There is a voltage regulator module mounted on the alternator case. I removed the key switch and found continuity in the "on" position but not in the "off" position. When not running and the key is "off", a voltmeter between the negative battery post and the negative battery cable reads 12.3 volts. I don t know how to test the voltage regulator module with a multimeter. But I did find that the red wire (the one with high temp silicone sealant on it) has continuity to the alternator case. That doesn t look good to me. Any thoughts? And what kind of alternator is this? Thanks.

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[JMOR]

(quoted from post at 17:04:02 02/10/20) The 12 volt conversion on my 641 has worked fine for 30 years. But now, the battery drains in a few days if I don t disconnect the negative (ground) cable. When running, the dash voltage gauge is pegged to the left (lowest reading). The battery is good. I had the alternator checked and it s good. I believe it was checked without the VR. I repaired the broken wire insulation issues in the picture. It didn t make a difference. There is a voltage regulator module mounted on the alternator case. I removed the key switch and found continuity in the "on" position but not in the "off" position. When not running and the key is "off", a voltmeter between the negative battery post and the negative battery cable reads 12.3 volts. I don t know how to test the voltage regulator module with a multimeter. But I did find that the red wire (the one with high temp silicone sealant on it) has continuity to the alternator case. That doesn t look good to me. Any thoughts? And what kind of alternator is this? Thanks.

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elco 10DN.
Remove red wire and repeat your continuity test. Be sure to test with both polarities of meter.

 

[UseFixUse]

The alternator is back on the tractor. I checked continuity between the disconnected red wire and the alternator case. At 200 ohms no continuity. At 20k ohms 1.52. At 2M ohms 0.001. I reversed the multimeter leads and got the same readings.

 

[Jim L WA]

Doesn't that alternator need a diode or lamp in the charging circuit? I would check there.

 

[JMOR]

(quoted from post at 20:46:22 02/10/20) Doesn't that alternator need a diode or lamp in the charging circuit? I would check there.

im, if you have to ask, that means that you don't know. So why muddy the waters? You are likely thinking of it as OEM install, which with this regulator, it is not. I did mean for him to measure the output stud of the alternator (as he did before) but without the red wire attached, not to measure the red wire.

 

[Jim L WA]

JMOR, you are obviously very knowledgeable about these 12 volt conversions. I didn't mean to "muddy the waters", but if one doesn't know something how would one learn by not asking questions.

 

[JMOR]

(quoted from post at 14:44:02 02/11/20) JMOR, you are obviously very knowledgeable about these 12 volt conversions. I didn't mean to "muddy the waters", but if one doesn't know something how would one learn by not asking questions.

ine, but I took it to mean that you were running him off on a wild goose chase, rather than looking in the right places. All is well.

 

[UseFixUse]

With the key off, the red VR wire hanging free, and batt. charge wire connected to the alt. batt. post, a voltmeter between the negative battery post and the negative battery cable starts at about 9 volts but decreases in several seconds to 0.1 volts. With reversed test leads, the reading is the same but with reversed polarity. The same test done earlier, but with the red VR wire connected to the alt. batt. post showed 12.3 volts steady.

 

[JMOR]

(quoted from post at 17:15:12 02/11/20) With the key off, the red VR wire hanging free, and batt. charge wire connected to the alt. batt. post, a voltmeter between the negative battery post and the negative battery cable starts at about 9 volts but decreases in several seconds to 0.1 volts. With reversed test leads, the reading is the same but with reversed polarity. The same test done earlier, but with the red VR wire connected to the alt. batt. post showed 12.3 volts steady.

arlieryou were checking continuity using Ohms scale, so now, why change to measuring volts???????
From those voltage readings, I say you are seeing a capacitor, inside the alternator, charging.

 

[UseFixUse]

(quoted from post at 15:04:18 02/11/20)

(quoted from post at 17:15:12 02/11/20) With the key off, the red VR wire hanging free, and batt. charge wire connected to the alt. batt. post, a voltmeter between the negative battery post and the negative battery cable starts at about 9 volts but decreases in several seconds to 0.1 volts. With reversed test leads, the reading is the same but with reversed polarity. The same test done earlier, but with the red VR wire connected to the alt. batt. post showed 12.3 volts steady.

arlieryou were checking continuity using Ohms scale, so now, why change to measuring volts???????
From those voltage readings, I say you are seeing a capacitor, inside the alternator, charging.

My fault. Your diagnosis can only be as good as my description. I ve done the following tests so far, all with the key off and the alternator mounted. 1. With pos batt cable on and neg batt cable off, and all wires connected to alt, a voltmeter between the negative battery post and the negative battery cable reads 12.3 volts steady. 2. I checked continuity between the disconnected VR red wire and the alternator case. At 200 ohms no continuity. At 20k ohms 1.52. At 2M ohms 0.001. 3. I just checked continuity between the alt output stud (no wires attached) and alt case and found no continuity at any setting. 4. I also did test 1 above but only with the the batt charging wire connected to the alt output stud (red VR wire not connected). The volt reading started higher but decreased in several seconds to 0.1 volts. It appears that the batt drain is 12.3 volts with all wires on alt but is only 0.1 volts with the red VR wire disconnected. On a side note, this alt does not need to be revved to make charge.

 

[JMOR]

(quoted from post at 19:25:54 02/11/20)

(quoted from post at 15:04:18 02/11/20)

(quoted from post at 17:15:12 02/11/20) With the key off, the red VR wire hanging free, and batt. charge wire connected to the alt. batt. post, a voltmeter between the negative battery post and the negative battery cable starts at about 9 volts but decreases in several seconds to 0.1 volts. With reversed test leads, the reading is the same but with reversed polarity. The same test done earlier, but with the red VR wire connected to the alt. batt. post showed 12.3 volts steady.

arlieryou were checking continuity using Ohms scale, so now, why change to measuring volts???????
From those voltage readings, I say you are seeing a capacitor, inside the alternator, charging.

My fault. Your diagnosis can only be as good as my description. I ve done the following tests so far, all with the key off and the alternator mounted. 1. With pos batt cable on and neg batt cable off, and all wires connected to alt, a voltmeter between the negative battery post and the negative battery cable reads 12.3 volts steady. 2. I checked continuity between the disconnected VR red wire and the alternator case. At 200 ohms no continuity. At 20k ohms 1.52. At 2M ohms 0.001. 3. I just checked continuity between the alt output stud (no wires attached) and alt case and found no continuity at any setting. 4. I also did test 1 above but only with the the batt charging wire connected to the alt output stud (red VR wire not connected). The volt reading started higher but decreased in several seconds to 0.1 volts. It appears that the batt drain is 12.3 volts with all wires on alt but is only 0.1 volts with the red VR wire disconnected. On a side note, this alt does not need to be revved to make charge.

F I follow you, then it sounds like thealt charges fine, but battery is drained by something. I expect that it is the VR. Disconnect all VR wires but leave alt to battery on alt stud. Now, is drain still there or not? You have then found the culprit.

 

[UseFixUse]

Thanks for the suggestions. I disconnected all VR wires but left the alt to batt on the alt stud like you advised. The steady 12.3 volt reading (drain) went away. However, the reading starts at about 9 volts and decreases in several seconds to 0.1 volts. Should there be any voltage reading in this test? I don t quite where to find a replacement VR module like pictured. I haven t found any online. Any thoughts on a replacement? There are no numbers visible on my VR. Also, are there multimeter tests I can use on my VR? With the VR in hand and all wires unconnected, there is no continuity between any two wires or any wire to the case.

 

[JMOR]

(quoted from post at 15:37:55 02/18/20) Thanks for the suggestions. I disconnected all VR wires but left the alt to batt on the alt stud like you advised. The steady 12.3 volt reading (drain) went away. However, the reading starts at about 9 volts and decreases in several seconds to 0.1 volts. Should there be any voltage reading in this test? I don t quite where to find a replacement VR module like pictured. I haven t found any online. Any thoughts on a replacement? There are no numbers visible on my VR. Also, are there multimeter tests I can use on my VR? With the VR in hand and all wires unconnected, there is no continuity between any two wires or any wire to the case.

ook here, but you can replace that alt with a 10-SI with built in VR & the whole thing will be less $ than this VR alone.
https://store.alternatorparts.com/search.aspx?find=10dn&category=2125

 

[UseFixUse]

(quoted from post at 13:04:30 02/18/20)

(quoted from post at 15:37:55 02/18/20) Thanks for the suggestions. I disconnected all VR wires but left the alt to batt on the alt stud like you advised. The steady 12.3 volt reading (drain) went away. However, the reading starts at about 9 volts and decreases in several seconds to 0.1 volts. Should there be any voltage reading in this test? I don t quite where to find a replacement VR module like pictured. I haven t found any online. Any thoughts on a replacement? There are no numbers visible on my VR. Also, are there multimeter tests I can use on my VR? With the VR in hand and all wires unconnected, there is no continuity between any two wires or any wire to the case.

ook here, but you can replace that alt with a 10-SI with built in VR & the whole thing will be less $ than this VR alone.
https://store.alternatorparts.com/search.aspx?find=10dn&category=2125

Good advice. I purchased a new 10SI alternator, installed my old alternator pulley and fan on it, and connected the 3 wires as follows. Large batt terminal goes to the large terminal on the top of the starter solenoid, which also connects to the fat positive battery cable. Terminal #1 goes through a marker lamp to the ignition switch "key on" terminal. Terminal #2 goes to the "always hot" terminal of the junction block. Then I connected the battery cables to the battery posts. I turned on the key, the dummy lamp lighted and the voltmeter read ~12.3 volts. I then started the engine. The dummy lamp went out and the voltmeter read just under 15 volts. Looking good! I shut the engine down, disconnected the negative battery cable and took am amp reading between the cable and the battery post. I got a constant 3.7 milliamp reading so I started disconnecting wires to find the drain. The drain stopped when I pulled the plug that goes to terminal #1 & #2 of the alternator. I also checked for continuity between any of the 4 terminals of the starter solenoid and found continuity only between the 2 small middle terminals, which is the coil, I believe. It appears the drain is from the alternator but I understand that it may be normal. I don t use the tractor for long periods of time. Hypothetically, if the sense wire (#2) was moved from the "always hot" side of the junction block to the switched side of the junction block to stop the drain with "key off", is there a potential issue? The sense signal would have to go through the ignition switch as well as the thinner ignition switch wiring. Any other issues? Thanks.

 

[JMOR]

(quoted from post at 19:08:22 03/03/20)

(quoted from post at 13:04:30 02/18/20)

(quoted from post at 15:37:55 02/18/20) Thanks for the suggestions. I disconnected all VR wires but left the alt to batt on the alt stud like you advised. The steady 12.3 volt reading (drain) went away. However, the reading starts at about 9 volts and decreases in several seconds to 0.1 volts. Should there be any voltage reading in this test? I don t quite where to find a replacement VR module like pictured. I haven t found any online. Any thoughts on a replacement? There are no numbers visible on my VR. Also, are there multimeter tests I can use on my VR? With the VR in hand and all wires unconnected, there is no continuity between any two wires or any wire to the case.

ook here, but you can replace that alt with a 10-SI with built in VR & the whole thing will be less $ than this VR alone.
https://store.alternatorparts.com/search.aspx?find=10dn&category=2125

Good advice. I purchased a new 10SI alternator, installed my old alternator pulley and fan on it, and connected the 3 wires as follows. Large batt terminal goes to the large terminal on the top of the starter solenoid, which also connects to the fat positive battery cable. Terminal #1 goes through a marker lamp to the ignition switch "key on" terminal. Terminal #2 goes to the "always hot" terminal of the junction block. Then I connected the battery cables to the battery posts. I turned on the key, the dummy lamp lighted and the voltmeter read ~12.3 volts. I then started the engine. The dummy lamp went out and the voltmeter read just under 15 volts. Looking good! I shut the engine down, disconnected the negative battery cable and took am amp reading between the cable and the battery post. I got a constant 3.7 milliamp reading so I started disconnecting wires to find the drain. The drain stopped when I pulled the plug that goes to terminal #1 & #2 of the alternator. I also checked for continuity between any of the 4 terminals of the starter solenoid and found continuity only between the 2 small middle terminals, which is the coil, I believe. It appears the drain is from the alternator but I understand that it may be normal. I don t use the tractor for long periods of time. Hypothetically, if the sense wire (#2) was moved from the "always hot" side of the junction block to the switched side of the junction block to stop the drain with "key off", is there a potential issue? The sense signal would have to go through the ignition switch as well as the thinner ignition switch wiring. Any other issues? Thanks.

hat should be fine. Surprise is the 3.7 milliampere, as that is generally more in the microampere range & would take better part of year to discharge a battery.

 

[UseFixUse]

I went ahead and connected the sense wire to the cool side of the junction block. Now, with key off, there is zero ampere drain. With key on, all other components function normally dummy light works, alt is excited and charging at ~14.7 volts. Please comment on any potential problems with this setup. Thanks you for your advice! Next project replace spindle in utility axle.

 

[JMOR]

(quoted from post at 16:09:33 03/04/20)
I went ahead and connected the sense wire to the cool side of the junction block. Now, with key off, there is zero ampere drain. With key on, all other components function normally dummy light works, alt is excited and charging at ~14.7 volts. Please comment on any potential problems with this setup. Thanks you for your advice! Next project replace spindle in utility axle.

our setup should be fine.