Changing alternator for EA82

I just changed the alternator on my '91 L-series. I'm just getting into DIY auto repairs, so please bare with me. My car has a 1.8L EA82 engine, with no power steering or a/c.

My question: Is a Hitachi LR150-200 alternator an appropriate replacement for my original LR160-137? Though I insisted that I get a part with the same number as the original, the guy at the junk yard (or 'wreckers' as they say here in Australia) claimed that the LR150 was appropriate. I installed the LR150 and it appears to be working, or at least, at roughly 2000rpm it got the voltage up to 13.77V.

My second question: Do the following voltages indicate a healthy battery and alternator? Here's how the voltages played out:

12.05V battery only, car off 10.25V starter engaged 12.05V car idling 13.77V ~2000 rpm +0.01V every 10 seconds that the car continued to run at 2000 rpm.
Reply to
John Newgard
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Assuming 20 degrees C, it should be closer to 14.5 volts. You could still have a good alternator if your battery is damaged from whatever ate the alternator or if your fanbelt is slipping.

I suspect your alternator is ok and your battery is either dead or near end-of-life.

Reply to
GrumpyOldGeek

It should be fine as long as the pulley is the same (swap with the old one if not), and the wiring harness plug mates with the receptacle on the alternator.

These numbers are with all other car electronics (headlights, r. defroster, heater fan, stereo) off?

I'd like to see a bit higher; 12.5V or so.

Probably OK, starters draw huge current.

Should be ~13.5V.

Should stay below ~14.5V as you rev the motor.

Battery charging?

Try disconnecting one terminal of the battery with the engine running. If it dies, the alternator isn't working. Try the same with the headlights and rear defroster on; if it dies, the alternator is weak (or you have bad/corroded connections). Try a known good battery (borrow one from someone), and see if the voltages come up, or simply drive the car for an hour or so (stay close to home ;-), and measure them again. If they come up, fine business, if they stay about the same, probably a weak battery, if they drop, and/or the engine dies, probably a bad alternator.

Finally, beware of your digital voltmeter; they typically have a very high input impedance. While this is a desirable feature for most things, it can mask poor connections, as the voltmeter isn't drawing any current to speak of. Best way to check for bad (high resistance) connections is to measure voltage drops with the circuit loaded (current flowing). Here is a real quick outline to get you started:

Headlights on, engine off. Connect negative voltmeter lead to clean chassis ground. Measure V at the battery + terminal; s/b~ 12.5V. Measure at the + clamp, s/b the same, if not, there is resistance in the connection (V=IR, V=0 if R=0), probably corrosion. Measure at the

- battery clamp, s/b 0V. If not, probably poor ground connection. Measure at the - battery terminal, s/b the same 0V, if not, suspect corrosion. Use this basic methodology to check voltages around the alternator circuit, headlight circuit, whatever; it is usually the fastest way to pin down bad connections.

Hope this is helpful.

ByeBye! S.

Steve Jernigan KG0MB Laboratory Manager Microelectronics Research University of Colorado (719) 262-3101

Reply to
S

With all due respect to Steve, who I think is a great resource for the group, I suggest that you don't try this. If you must, do is at the lowest possible idle speed and as much electronics as possible turned off. Removing the battery with the engine running creates a "load dump" voltage spike that can be very stressful to the car electronics.

Swapping the battery is a much safer alternative. More than once I've seen a bad alternator take a battery to the graveyard with it.

Reply to
Jim Stewart

Wow! Thanks for the great advice fellas. I'll test things out and get back to you. FYI, I tested the new alternator out this weekend with a

800-km road trip :-) and didn't have any problems.
Reply to
John Newgard

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