Alternator question., Not Charging. |
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Alternator question., Not Charging. |
Olympic 914 |
Mar 25 2018, 05:05 PM
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#1
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Group: Members Posts: 1,710 Joined: 7-July 11 From: Pittsburgh PA Member No.: 13,287 Region Association: North East States |
Took the car out for a drive today, planning on going to dinner. everything is working as it should. getting on the PA turnpike and I had to accelerate briskly to get into traffic, and a moment later I noticed that the RED alternator light had come on. Pulled of at a wide spot to check the belt and wires and shut it off. Not checking the belt with it running. Belt good, plug tight, tapped the VR a couple times for good measure and started it back up. Light still on and now my Autometer AFR gauge just had bars. I know that is because it doesn't turn on until the voltage is +13v So not charging.
Now I am on a limited access highway with the next exit `12-15 miles away. Good thing had the battery fully charged on the tender before I left the house. So I made it to the next exit, turned around and headed back home for a total of 35 miles on battery only. Whew. But that shot dinner..... Replace the VR with another I had that previously tested good. still no charging. checked the plug on the relay plate again. looks good. I have not yet checked the wire connections at the alternator, possibly a wire vibrated loose during the brisk acceleration. Now the question I read to test the VR to short between D+ and DF and if the alternator is good voltage at the battery will go to alternator maximum of about 15-16V So do I REMOVE the VR for this test? and jump between the D+ and DF at the relay plate. OR Leave the VR in place and short between those pins? |
Gatornapper |
Sep 4 2019, 05:28 PM
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#2
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Senior Member Group: Members Posts: 1,263 Joined: 22-September 17 From: Woods west of Richmond, VA Member No.: 21,449 Region Association: South East States |
Ok, test results:
Relay board not the problem......zero resistance between the D+, D-, and DF at the VR contacts and their matching points at the cable to the alternator end. No corrosion or even dust at any of the contact points - but then I had cleaned them with electrical contact cleaner anyway. Also, voltage between battery ground and engine while running is .007 volt......essentially nothing. Ran separate ground from engine to chassis, no change in anything. Only thing left is the VR as far as I can see things...... Long wait until next Tuesday. GN |
Spoke |
Sep 4 2019, 07:24 PM
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#3
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Jerry Group: Members Posts: 7,107 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
Ok, test results: Relay board not the problem......zero resistance between the D+, D-, and DF at the VR contacts and their matching points at the cable to the alternator end. No corrosion or even dust at any of the contact points - but then I had cleaned them with electrical contact cleaner anyway. Also, voltage between battery ground and engine while running is .007 volt......essentially nothing. Ran separate ground from engine to chassis, no change in anything. Only thing left is the VR as far as I can see things...... Long wait until next Tuesday. GN Good to check voltage from battery ground to engine is low. For the alternator, the important measurement is from the alternator case to battery ground/chassis. By measuring D- to chassis before you have done this test. See the schematic below. Notice the D- wire at the VR goes into the alternator and directly to ground. That ground is actually: The alternator case to fan shroud to engine case to transmission case to transmission wire strap to chassis ground. So measuring D- to chassis measures the total voltage drop of all those components. If you see less than about 0.2V drop from D- to chassis while the alternator is working, the alternator is properly grounded. Keep in mind that without the alternator working, there is no current in the alternator to chassis ground so a zero volt reading would be expected even if the alternator ground is not good. The best way to ground the alternator is to run a wire from the alternator case to chassis. This is especially important if you have painted or powdercoated the fan shroud. Right Zach? Attached thumbnail(s) |
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