Voltage Regulator Failed?

[Maticuno]

So this morning I started the car and had the three dash lights of doom pop up. Other than brushes I don't think there is anything that would fail inside of the alternator other than the voltage regulator. What would cause a voltage regulator to just suddenly take a dive? Hoping for a cheap fix I replaced the alternator/battery wire with a 6 gauge wire to no avail, obviously not a corrosion issue.

[Timon]

As of right now your car still runs and drives fine, right?

If it does run and drive, you only have another day or two to figure out what you plan to do. Mine lasted 2 days after with no issues except the lights flickering at idle (only when fully warmed up). On the 3rd day, omw back from work everything starting dimming, dash lights, headlights, and radio lights. The key that let me know it was the voltage regulator as opposed to anything else was the fact my battery gauge was dropping slowly the entire time while the lights were dimming.

I'd suggest having it rebuilt by a shop, but to me that was too expensive, estimated at $90-$160. Your next best bet is to find a used alternator (there are like 4 or 5 from other Toyotas that swap right over), which is what I did. Mine did come from another MR2, mileage unknown, for $40, with a 90-day warranty. I've only had it in about 3 weeks or so, but I haven't had any issues with it. When it goes again, assuming money allows, I'll have it rebuilt.

The voltage regulator is actually really easy to get off if you can find one that will fit. Remove the outside housing, iirc 7mm bolts, and the regulator is right there held in by small phillips head screws.

If you end up replacing the alternator you'll know immediately after dropping it if it will be cake or not. If you unbolt it, and it falls off the bracket - cake. If you unbolt it, and have to wiggle and tug on it to get it off the bracket - hell. Get a helper at this point for installing the new one as it will have to be hammered in with a 2x4 from the top, and someone on the bottom will have to slide the pivot bolt in. I did it alone, at a cost of nearly 45 minutes going from the top of the car to the bottom of the car trying to get the pivot bolt in.

This should help too,
MKI MR2 Write-ups .

Good luck.

[Maticuno]

Car still runs fine. The battery gauge is slowly dropping so hopefully it is the voltage regulator. I have one on order, should be here tomorrow. I'm still curious though as to what would cause the regulator to fail. There aren't any moving parts and as far as heat, it's on the intake side of the engine so it shouldn't be getting that hot.

[Jackstand Queen]

I owned an N.A. for about 7 years. I only put about 50,000 miles on it. This is significant because in that amount of time and mileage, I replaced the alternator at least 3 times!

I always bought a remanufactured one from Napa, or another major parts retailer.

I think they went out so often due to the high revving nature of the 4age. Big main pulley spins small alternator pulley multiples of times faster than engine RPM.

I try to avoid buying OEM parts from a Toyota dealer. But I wonder if this was one of those times I should have gone to the dealer for the part.

My answer to the question of why electronic components like a voltage regulator fail is:
1. we live in an ocean of corrosive elements: oxygen is primary.
2. electromagnetic radiation (which includes infrared radiation from an exhaust) degrades man-made materials in a process related to entropy
3. electronics have a shelf life of perhaps a half century if not used, kept in a cool, dry storage conditions.

[Timon]

Originally Posted by Jackstand Queen

I owned an N.A. for about 7 years. I only put about 50,000 miles on it. This is significant because in that amount of time and mileage, I replaced the alternator at least 3 times!

I always bought a remanufactured one from Napa, or another major parts retailer.

I think they went out so often due to the high revving nature of the 4age. Big main pulley spins small alternator pulley multiples of times faster than engine RPM.

I try to avoid buying OEM parts from a Toyota dealer. But I wonder if this was one of those times I should have gone to the dealer for the part.

I'd have to agree you should've gone oem or rebuilt. Honestly, it works just as well to have it rebuilt if done by a reputable shop.

I'm starting to think mr2tim is right when he said that water drips from the engine lid directly onto the alternator, which would explain why it seems to always be the voltage regulator that goes out on them. I'm thinking this may be something to look into.

[85BlueMK1]

Same thing happened top me. Took off the alternator -not fun- had it rebuilt. Rebuilder found a shorted stator. Put alternator back on and it lasted one day. Off it comes again and needs a voltage regulator. New regulator goes out almost immediately. Again it comes off and another regulator installed. Didn't even get it out of the garage this time. Finally went with a Denso re-manufactured alternator. Everything now OK. Changing these things is a PITA!!!! Especially if its a tight fit between the alternator and the bracket as previously mentioned. Each time I removed and installed the alternator the job seemed to get harder rather than easier. Which I knew what caused the original to fail but I already spent a fortune trying to fix it!

[Maticuno]

Voltage regulator replaced (which can be done without removing the alternator I found out), but no help. Still the three dash lights, but now a new symptom. The lights only come on while the engine is idling. Soon as I tap the gas they go out. It is also idling about 200 RPM higher than normal (1200 instead of 1000). Brushes were still in good shape so I reused them. Multimeter shows 12.2V engine off, 11.6V engine running.

[jfries89]

i had this problem. for me it turned out that the black/yellow wire on the voltage regulator had too much resistance and wasn't telling the alternator to turn on or whatever. so u may want to check that

[Maticuno]

Did you replace the entire wire or did you find a spot with corrosion and splice it there.

[jfries89]

i ended up stripping off some of the wire covering and soldering another wire on to it and running it to the fuse box that's in the engine bay because you need to find a wire that is cold when the car is off and hot when its on

[Maticuno]

Ran a new wire to replace the b/y one and still nothing. Looks like I need an OEM alternator.

[Timon]

I'm thinking it'd be really easy to do a makeshift shield around the alternator while it's out, granted I won't bother with this unless I have another one go out and need to replace it or until summertime rolls around.

[Maticuno]

Is there a way to tell if the alternator is an original NipponDenso type or a cheap Vatozone rebuild? I've noticed on the back cover some have the "ND" logo while others have the "ND" logo with three little dots above it.

[mr2tim]

Dudes, like Timon indicated it's the water dripping down from the hole (vent) on the N/A engine cover, the water shorts the wiring on the internal voltage regulator. Timon's idea for a Alternator shield (umbrella?) in lieu of modifying the engine covers pass side vent drainage might be easier for most folks.

Let's not get carried away, it's defectively engineered senario. Remember these dudes lost World War 2 because they made cheap airplanes and lost the air war.

[Maticuno]

A Toyota rebuild from Aaron at Lithia Toyota installed and working perfectly. It's so nice now to not have my 2's ass stuck up in the air (up on ramps). There was absolutely NO WAY I was going to get the alternator to fit into the bracket, even with me underneath guiding and my wife up top tapping on it with a 2X4. So I took an angle grinder with a very fine grit flap disk and just shaved a RCH off the alternator. Even with that I still had to smack it in with the 2X4 and wiggle it around for about five minutes aligning the bolt hole.