Printable Version of Topic

Click here to view this topic in its original format

914World.com _ 914World Garage _ Weird electrical problem

Posted by: Dtjaden May 14 2015, 10:57 PM

A couple of weeks ago I started a drive with the regional PCA group after about 100 miles at sometimes high speeds I noticed that I was developing an engine ping under load (I have Megasquirt engine management). Looking at my gauges, while my AFR was normal to slightly rich my voltage meter was running low, about 11 volts.

At this point I turned around and managed to make it back home. The next morning my battery was dead so I used this as an excuse to install an Optima battery. After installing the new battery I noticed that the alternator light was lite when the car was NOT running and went out once the car was running. However using a multimeter the battery was not being charged.

I expect that the fact that the alternator light was lite with the ignition switch off was the reason the battery drained overnight.

I checked all of my fuses and all were OK. I haven't had any time in the last couple of weeks to do any further testing but since I have a spare ignition switch I plan to replace it as a matter of course. If that does not solve the no-charge situation I will need to start troubleshooting the charging circuit. I believe that the ping may have been caused by the Megasquirt management system being unhappy with the low voltage.

Has anyone had a similar problem? Any advice about troubleshooting this problem?

Darryl

Posted by: bandjoey May 14 2015, 11:05 PM

Bad regulator? On the relay board. Have u checked it?

Posted by: Michael N May 14 2015, 11:36 PM

Check the voltage regulator. I knocked mine out of its socket on the relay board last year and it cause the car not to charge. I was getting ready to replace the alternator with the info from this board I saved myself a lot of extra work and money. Pull it out and reseat it in the relay board. Make sure contacts are clean.

Posted by: Tom May 15 2015, 03:21 AM

Darryl,
The alternator light would take considerably longer than overnight to discharge your battery. A battery with @50 A/H capacity with a load of the alternator light only ( about 0.15 amps) would take (50 divided by 0.15 = 333.33 hours) to give you the time frame. Well over a week.
It sounds more likely your ignition switch is bad and causing all electrical systems to be ON even with the switch turned to OFF. So I would agree that changing out the switch would be a good place to start.
Tom

Posted by: bulitt May 15 2015, 05:48 AM

You may have a bad diode in your alternator.

Posted by: Dtjaden May 15 2015, 08:02 AM

Thanks everyone. I will get to the car next week and I will post what I find.

Darryl

Posted by: Chris Pincetich May 15 2015, 08:37 AM

There's info on using a tester wire to jumper the voltage regulator on the relay board in this thread I started.
http://www.914world.com/bbs2/index.php?showtopic=250066&hl=alternator

Good luck!