Would an alternator be the cause of this?

[ThomasH]

standard feature on any fluke ive owned. course thats a $150 meter not a free one from Harbor freight with coupon.

There are some multi-meters that have response time on a min-max reading that gets into the hundreds of micro-seconds. So if you have one of those, you can see the highest value of a not too short transient. Not much else, but you can see that.

 

[Soundguy]

Unfortunately a multimeter will not show any voltage spikes that the alternator is putting out, as multimeters average out voltage to give you a fairly stable number. It takes a scope to see spikes, which can and will do lots of electrical damage to lights, the PCM, etc.

While technically correct, the basics of the statement tend to not work that way.

Sure, you can get a micro duration spike that the sample rate of the meter misses.. but remember.. that huge thing in the circuit. oh yeah.. the LOAD and the storage battery.

Both those serve to physically averave out incoming voltage that is not steady state.

Look at half wave rectifier chargers. constant bump as you get only 1 positive half of a wave form.

Lotsa cheap bat chargers are half wave, and yet they still manage to charge a battery up.

Any spike thrown off by an alt that is going to hurt auto electronics will also be picked up by a meter.

Look at your alternator capacity. As the voltage it puts out goes up past the battery charge voltage, that battery becomes a SUBSTANTIAL load.

If a meter is showing voltage in the 14v range, I'd move my focus to poor connections.

if this is a GM ( i think I read it was ), look real hard at the back of those headlamp clusters... some pretty pathetic design went into the multi part connectors, and they scrimped on the wire size too. Just barley big enough, and just barely works are the two main tech's that went into that design!

 

[Soundguy]

There are some multi-meters that have response time on a min-max reading that gets into the hundreds of micro-seconds. So if you have one of those, you can see the highest value of a not too short transient. Not much else, but you can see that.

remember, you can get graphing o-scope meters too.

The 5$ HF ones aren't too snazzy.. but there are plenty of higher end industrial and commercial meters out there up to the task.

 

[Soundguy]

standard feature on any fluke ive owned. course thats a $150 meter not a free one from Harbor freight with coupon.

exactly!

 

[fitter1]

Over time the light sockets get corroded and cause premature light failure and need to be cleaned or replaced.

 

[ThomasH]

While technically correct, the basics of the statement tend to not work that way.
/snip

Well you and I will have to disagree. I have done replacement computers on more than vehicle that had high transient spikes coming from a defective alternator. In addition, one blew out an instrument cluster AND body control computer (Chrysler Pacifica). All of these required a really fast meter or a scope to troubleshoot, hardly the type of thing you buy from a mass merchandiser...

 

[Coyote machine]

Just verify voltage at the battery with whatever meter you have. Report back results.
Make sure that battery ends are clean and tight, and all grounds are clean and tight too.
Chances are, if your alternator is overcharging it will show up as too high voltage back to the meter/battery. You may have a bad diode or voltage regulator. As mentioned, other connections at the headlamps, etc, could be causing burnouts, but all the bulbs you're burning out it's less likely.

 

[Soundguy]

Well you and I will have to disagree. I have done replacement computers on more than vehicle that had high transient spikes coming from a defective alternator. In addition, one blew out an instrument cluster AND body control computer (Chrysler Pacifica). All of these required a really fast meter or a scope to troubleshoot, hardly the type of thing you buy from a mass merchandiser...

I never said to buy a cheap meter from a mass seller, I said to get a quality industrial grade meter, not a consumer grade.

As for the spikes taking out an ecm, its not a cut/dry issue.

Some vehicles have significant CM interaction with the alternator. If the spike occurs on the control circuit side, sure.. There is no extra load there to absorb it, just some small glass. This is in stark difference to a spike on the charge/load side that has quite a bit of components with which to clamp that spike.

So I don't think we are really disagreeing, you can't have an intricate discussion on all facets of logic level electronics, coupled with large load electronics and gloss over it in a couple emails

 

[crazyal]

Have you looked into the price of a new alternator? You could spend more money on a nice piece of test equipment than just replacing the alternator. If it's happening all the time then it would be easy to pick up but if the spikes are happening once a day or once a week you would need to have test equipment connected to the car all the time and be able to record the event. I'm not usually the shot gun kind of person but if your vehicle is more than a couple years old and an alternator is pretty cheap then I would replace it. Another option would be to go to Autozone and have them connect it up to their analyzer and hope that any spike happens while it's connected up. Don't get me wrong, I love tools but if you only have a one time use for them it can get very expensive.