Alternator charging?

[Michael M.]

I just replaced my engine compartment harnesses (ignition and forward lamp) as well as all of the vacuum hoses. The car starts and runs fine, all lights work, horns work, etc.

I am concerned that a few of my secondary gauges are not working (temp and ammeter). I suspect this is a grounding issue and I will be investigating this coming weekend (my dash was in pieces while replacing the vacuum hoses, fiber optics, headlight switch, etc.).

Years ago the car was converted to utilize an SI style alternator and when I replaced my harnesses I bought the conversion harness adaptors from Lectric Limited.

I have a voltmeter and test light. How can use these to verify the alternator is putting out what it should and charging the battery as the car is running. Is it possible to isolate that possibly the alternator is operating properly but somehow the charge isn't reaching the battery?

Thanks for any replies.

[Duke W.]

Re: Alternator charging?

At idle measure voltage between the alternator output stud and housing and between the battery posts. Both should read about the same and be between 13.5 and 14.5 volts.

Duke

[Michael M.]

Re: Alternator charging?

Thanks Duke. I'll test it tonight and see. If I turn on the lights while the engine is running should the voltage momentarily drop and then recover?

[Duke W.]

Re: Alternator charging?

You might see a momentary drop, but the alternator should maintain proper system voltage at idle even with the lights on.

Alternators are rated at 5000 RPM rotor speed, and the drive ratio is typically in the range of 2-2.5 times engine speed, so at 500 PRM idle the rotor speed should be up to 1250 RPM and the output should be at least half rated capacity. SHP engine alternator drive ratios are typically at the lower end of this range due to their higher idle speed, while base engines that idle at low speed are at the top end of this range.

At 2000 engine RPM the alternator should be capable of delivering near maximum output if the load is actually this high. So another test you can run is to turn on every electrical device possible and check the minimum speed that will maintain system voltage in the proper range.

Duke

[Michael M.]

Re: Alternator charging?

Thanks Duke. We'll see how it goes.