 Voltage drop problem |
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| jvmarino |
 Sep 5 2024, 07:38 PM
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#1
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Member  Group: Members Posts: 96 Joined: 22-March 09 From: Baltimore Member No.: 10,188 Region Association: None  |
Driving the 914 today I noticed an issue with voltage drop for the first time. Car starts up fine, runs good as usual, but when rpm goes over about 3600, the volt gauge has a noticeable drop down to about 12v indicated. Generator light also comes on. When rpm goes back below 3600, light turns off and volt gauge jumps back up about 1.5 volts.
My initial thought was a loose alternator belt, as I haven’t touched it since rebuilding car almost 30 years ago. Felt the belt and it seemed too slack. So tonight I tackled this project and after about an hour of cursing at the lower 13mm bolt, I finally found a way to loosen it. I get the belt tightened and button everything back up. Fire car up and it still does the same volt drop thing. Anyone here have any thoughts on what the problem is. Car still drives fine, but I don’t want to take it anywhere until this is solved as it would stink if it completely dies on me while using it. Jim |
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| jvmarino |
Oct 5 2024, 01:27 PM
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#2
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Member Group: Members Posts: 96 Joined: 22-March 09 From: Baltimore Member No.: 10,188 Region Association: None |
Well I finally got around to some testing after some delays. First I jumpered DF to D+, hooked meter to battery and started car. Voltage started above 14v and running rpm up over 4K the voltage went up over 18v. I then removed jumper and plugged VR back in and car was running about 13.6v and at high rpm dropped down between 13.1 & 13.3. The GEN light still came on at high rpm’s.
Did not do what I thought it would when using the jumper. Any thoughts from those with better experience than me? |
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| Spoke |
Oct 7 2024, 07:30 AM
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#3
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Jerry Group: Members Posts: 7,106 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None 
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QUOTE(jvmarino @ Oct 5 2024, 03:27 PM)  Well I finally got around to some testing after some delays. First I jumpered DF to D+, hooked meter to battery and started car. Voltage started above 14v and running rpm up over 4K the voltage went up over 18v. I then removed jumper and plugged VR back in and car was running about 13.6v and at high rpm dropped down between 13.1 & 13.3. The GEN light still came on at high rpm’s. Did not do what I thought it would when using the jumper. Any thoughts from those with better experience than me? The voltage at the battery seems in the correct range for maximum alternator output which is the point of the DF to D+ test. Was the GEN light on during the test at all? That you have tried 2 different VRs seems to point to the alternator as the issue. |
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Posts in this topic
jvmarino Voltage drop problem Sep 5 2024, 07:38 PM
technicalninja Full field the alternator at 2500 rpm and see what... Sep 5 2024, 07:54 PM jvmarino Well I picked up a good deal on a solid state regu... Sep 16 2024, 04:59 PM GregAmy Sounds like this one from last week:
http://www.9... Sep 17 2024, 06:27 AM jvmarino I am by no means an expert on car charging systems... Sep 17 2024, 12:22 PM
Spoke was due to worn brushes in the alternator.
It alm... Sep 18 2024, 11:43 AM jvmarino
was due to worn brushes in the alternator.
It al... Sep 18 2024, 01:02 PM Spoke
[quote name='Spoke' post='3168494' date='Sep 18 2... Sep 18 2024, 01:43 PM StarBear Yep; same thing with my DD 2009 Camry. Fortunately... Sep 18 2024, 02:05 PM jvmarino Read through some more old threads on the forum an... Oct 6 2024, 11:29 AM Spoke
Read through some more old threads on the forum a... Oct 7 2024, 07:38 AM jvmarino The GEN light comes on when key is in before car s... Oct 7 2024, 07:38 AM davep While the alternator may have diode issues, please... Oct 8 2024, 09:55 AM |
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