First, the '93-
When the bat light was on and the voltage 11.2, did it jump back up when you rev'ed the engine? If so, that's not out of the ordinary - sometimes the alternator does't start right up, or a brush got stuck. I would keep an eye on it - if it does it again, replace the VR. Otherwise, I'd think about replacing it at some convienent time. You can usually do it with the alternator in the car. You can access the VR from underneath or above. I prefer above, but you need thin arms. Disconnect the negative lead of the battery first!

The voltage moving around between 12.9 and 13.6/9 is normal. With a cold engine and at higher revs, 13.9 is reasonable. A warm car at idle, with a few accessories on, I can see 12.9. If you're driving along and the engine is at 2K rpm or above, I would expect to see 13.0 or more. But the voltage changes with load, speed, and temperature under the hood.

As to the '92 - What you're looking at is the startup voltage. The EDU grabs a voltage while the engine is cranking. It is a rough indication of battery health. Absolute numbers don't help much here - every car is different. I have had cars where 9.5 meant I needed a new battery - I've got another where a brand new battery reads 9.0, and it's low 8 volts before I know the battery is bad.

You most probably aren't seeing the battery lose power. Instead, what you're seeing is that a warm engine starts faster and easier than a cold one. A warm engine presents less of a cranking load, and the fuel pressure is already up, so it catches sooner. The EDU grabs the voltage at some point, and the engine may already be turning fast enough for the alternator to be providing some voltage. So it's quite normal to see a 'start up' voltage higher with a warm engine. No worries.

posted by 192.249....

• Do I replace Voltage Regulator?, aaron, Thu, 17 Mar 2005 06:38:53
  • REV update on alternator - revving did correct it..., aaron, Thu, 17 Mar 2005 13:17:40
    • Replace it, Ari , Fri, 18 Mar 2005 08:21:21
    • Re: REV update on alternator - revving did correct it..., RalphS, Thu, 17 Mar 2005 14:50:45
  • Re: Do I replace Voltage Regulator?, RalphS, Thu, 17 Mar 2005 12:38:44
  • Re: Do I replace Voltage Regulator?, Air, Thu, 17 Mar 2005 07:22:27 <-- Viewing This Message
    • I didn't rev, per se, I just started to drive away..., aaron, Thu, 17 Mar 2005 08:11:53
    • Thanks Air and Rachel for quick and helpful responses, aaron, Thu, 17 Mar 2005 08:09:23
  • Re: Do I replace Voltage Regulator?, rhale, Thu, 17 Mar 2005 07:12:50
    • Re: Do I replace Voltage Regulator?, Yaofeng, Thu, 17 Mar 2005 08:58:18
  • Re: Do I replace Voltage Regulator?, Yaofeng, Thu, 17 Mar 2005 06:58:25
    • How to check battery age?, aaron, Thu, 17 Mar 2005 08:15:12
      • Re: How to check battery age?, Yaofeng, Thu, 17 Mar 2005 08:40:47
        • i'll try swapping batteries to see if it changes..., aaron, Thu, 17 Mar 2005 19:25:57
      • You're only as old as you feel, Ari , Thu, 17 Mar 2005 08:20:06
        • Fluctuating, Tapani, Fri, 18 Mar 2005 01:01:27

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