Changing alternator for EA82

J

John Newgard

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.
 
John said:
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.

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.
 
Hi John!

My question: Is a Hitachi LR150-200 alternator an appropriate
replacement for my original LR160-137?

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

These numbers are with all other car electronics (headlights, r.
defroster, heater fan, stereo) off?
12.05V battery only, car off

I'd like to see a bit higher; 12.5V or so.
10.25V starter engaged

Probably OK, starters draw huge current.
12.05V car idling

Should be ~13.5V.
13.77V ~2000 rpm

Should stay below ~14.5V as you rev the motor.
+0.01V every 10 seconds that the car continued to run at 2000 rpm.

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
 
S said:
Hi John!




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).

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.
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.

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.
 
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.
 

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