The alternator replacement thread, Fixed! |
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The alternator replacement thread, Fixed! |
VaccaRabite |
Aug 12 2018, 07:07 PM
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#1
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En Garde! Group: Admin Posts: 13,444 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
Waiting on the side of the road for a flatbed to take me home.
Engine ran great. Charging system not so much. Driving along. Lights started going dim. Car started bucking. Only 5 miles to home but it wasn’t going to make it, and no shoulders to pull over safe on the little farm roads. So I pulled into a spot I knew of and shut it down and parked it and now I wait. McMark had said earlier he wasn’t sure about the charging system. But the alt light was not on and no issues before now. So. What’s the alternator I need to buy? Maybe a new VR as well? I guess I should test the battery and make sure it’s okay too. Zach |
VaccaRabite |
Aug 27 2018, 05:04 PM
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#2
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En Garde! Group: Admin Posts: 13,444 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
I got Epstien's package in the mail today. So that was a good excuse to fiddle with the car after work.
I tested continuity from the alternator to the engine block and to the body. Very strong continuity, about one ohm resistance from the alternator case to the body. From the transmission to the body was basically zero resistance (there was a very small number on the screen of my meter). So, gounding was not an issue. I replaced the board with a new one from Mark and put everything back. I am using the new solid state VR. Started the car, and was measuring 12.6 volts at the battery on the meter at warm idle. Unplugged the VR and it dropped to 12 volts on the battery, and the engine idle speed increased slightly. So the car IS charging at idle. Bring the throttle up to 4K rpm, and voltage dropped to 12.05 volts. So back to its old tricks. With all my lights on (driving lights, head lights, flashers) and the engine at 4K rpm I was only making 11.3 volts at the battery. Unplugged the VR again and shorted DF to D+ and was making 14 volts at idle and the engine idle lowered noticeably. I had my laptop plugged in and talking to the ECU, and the ECU is seeing about .6 volts less then my meter is seeing across the battery terminals. The tuning software was occationaly flashing the red "charging" flag. At this place, I have replaced: Alternator VR (several times) relay board Alternator harness I have confirmed that all the engine compartment grounds are in good shape. About the only thing I can think to do at this time is add a ground wire from the alt to the engine case, but I really doubt that's my issue at this point. :-/ The other option is a bigger alternator (70 amp maybe?). Is it at all possible that my battery is the issue? I'm using a Odessey race battery. Thinking out loud. Is it at all possible that the alternator I put in (that I got from @bdstone914 ) was internally regulated? Would double regulation do what I am seeing? How would I tell? @spoke @ClayPerrine Zach |
Spoke |
Aug 28 2018, 04:53 AM
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#3
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Jerry Group: Members Posts: 6,978 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
one ohm resistance from the alternator case to the body. From the transmission to the body was basically zero resistance (there was a very small number on the screen of my meter). So, gounding was not an issue. If you're measuring one ohm between the alt case and engine block, this should be considered a very large resistance. If indeed you have 1 ohm resistance between alt case and engine block, this would account for strange behavior and not as much voltage applied to the battery. Ohms law is V = I x R. With 1 ohm if there is 1 amp of charging current, there will be 1V drop in a system where the difference between 1-2V is huge. You can test to see if you have a voltage drop from alt case to chassis by measuring at the VR from D- to chassis. See the schematic below where D- at the VR is connected to the alt case. Short D+ to DF; start the car and measure voltage from D- to chassis. There's a chassis stud right by the relay board. You should read zero volts or near there. Attached thumbnail(s) |
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