How To: Replace Alternator

Note: This only pertains to the N/A MKI MR2s since the SCs alternator is located on the exhaust side of the engine.

  • Got the 3 warning lights (Charge, Cooling Fan, Brake) on your dash shining in your face? Bad voltage regulator that is built into the alternator.
  • Got one warning light (Charge) on? But don’t notice a drop in the voltage gauge? Possibly a bad diode in the alternator
  • Got one warning light (Charge) on? Notice a drop in the voltage gauge? Alternator itself is possibly bad.
  • Any of those three could also be bad connections to the alternator, so do some diagnosis before getting your hands real dirty.

Removal

1) Disconnect battery by removing the negative cable

2) Remove the 2 hoses leading to the coolant reservoir. Then remove the reservoir by pulling straight up. May be a little tough if you haven’t removed it in a while, but keep yanking.

3) Now you can clearly see the alternator (and my obvious water pump leak…) Remove the three 12mm bolts. The 2 red ones are a little tough to reach. But removing the adjuster bracket completely makes removal of the alternator a lot easier later on. Also remove the oil dipstick as it gets in the way.

4) Now you should be able to pivot the alternator, so that you can remove the belt. If not, you may have to loosen the pivot nut underneath in step 5. Also, unplug the circled sensor wire.

5) Now get under the car. Unplug the green circled connector. It has a little tab you have to squeeze and then pull out. Pull away the cover over the red circled connector and then remove the 10mm nut that holds the wire on. Now move to the pivot nut and bolt. It will probably take both a 14mm socket and wrench to get them loose.

Once you got all that done, still from underneath the car try wiggling the alternator back and forth pushing it up, to remove it from the pivot bracket. Some alternators may be in there pretty dang tight, so keep working it till you get it out.

(mmmmm….look at all that tasty coolant)

6) Once it’s free of the pivot bracket, remove the alternator from the engine bay from up top. It may take some finaggling around, but it comes out.

Here’s just a view from the top with the alternator out.

And here’s the alternator parts removed.

Installation

It’s basically just the opposite of the removal process.

1) From above place the alternator into position of the pivot bracket.

2) From below make sure the alternator is lined up with the bracket, and pull it down into place. Again this may be harder for some. My first replacement alternator needed to be forced back in with a block of wood and a hammer from the top. If it is this tight for you, you may need another person using the hammer while you are underneath lining up the pivot bolt and bracket. Do not fully tighten up the bolt and nut once you get it in there.

3) Now back up top reinstall the adjustment bracket. The 2 bolts that hold it to the engine first, but don’t tighten completely. Then line up the alternator with the bracket and install the bolt, not tightening completely. Now you can tighten the 2 adjustment bracket bolts down.

4) Go ahead and install the 3 different wires and plugs that you removed. And replace the alternator belt. Make sure of course everything is lined up properly with the belt.

5) Tightening the belt. This is most likely not the recommended way to do this, but hey it works. Don’t blame me if you break something though. Take a big screwdriver or some other pry bar and pry the alternator in either of the 2 spots, pushing the alternator back and tightening the belt. Once you think it’s tight enough tighten down the adjustment bolt. Proper way is to test if the belt is tight enough is a belt tensioner gauge. It may take another person to hold the pry bar while you tighten the adjuster bolt.

6) Once you are satisfied with this, tighten the pivot bolt back underneath the car.

7) Replace the oil dip stick, and the negative battery cable.

8) Start her up. If you notice any squeals coming from the alternator area, you didn’t tighten the belt enough. Get out yer big pry stick again and tighten it up some more. Of course turn off the car before doing this πŸ™‚

This documentation in no way replaces the Toyota MR2 Repair Manuals. The purpose of this content is only to provide supplementary information to fellow MR2 enthusiasts. Midship Runabout and its contributing authors will not be held responsible for any injury or damages that may occur as the result of practicing any of the methods or procedures described within this website. Article and photo submissions are property of the contributing author.


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