I got my alternator checked in my '86SE auto, V6 and it came back with a "bad diode".

My questions are these:

1) how long do I have before it goes "caput"?
2) if I keep driving the car with an alternator with a bad diode, will that screw up anything else (i.e., stereo components, charging system, etc.)?
3) I'm assuming that the alternator that's currently in the car is a stock one. What brand/kind/size should I get to power an upgraded stereo system w/ amps, sub, CD player, DVD player & LCD screen?
4) how do you remove and replace an alternator in the V6? I've done it in my old 4cyl '88, but I'm not too familiar with the 6cyl engines yet. (I checked the Haynes manual and it didn't provide too many details.)

I'm trying to decide my next course of action. I don't really have anywhere to work on the car here, so I'd have to find a place to do everything and I don't want to take the car someplace to work on it and then get stuck if it takes longer to do or something doesn't "fit" right.

Thanks in advance for all your help guys!

~Tress

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I may not know alot about cars...but I make a Fiero look good!

"The Hottie" --drowned by Hurricane Katrina but not forgotten: "Memories are forever"; The Hottie Diaries: (A Tribute to my little car)
Preface: Babes Do It Better Volume I: Checkup Ups and Downs: It Runs, Sort of Volume II: Engine Adventures Volume III: Declaration of Independence ...to be continued (she will live again)

a bad diode will cause the battery to drain. it's easy and cheap to replace, takes about as long to R&R the alternator as to rebuild it. just go ahead and do the whole thing at once, brushes, diode, regulator, bearings. this will save you from having to pull it again in 6 months, not to mention having to get it home after it dies on the road.

Usually you can 'hear' when a diode is bad. GM alternators develop a 'whine' or 'whistle' noise that follows the engine RPM. It gets higher pitched as the RPM's increase.

There are six diodes in an alternator pack. GM alternators are 3 phase with two diodes for each phase. If just one diode goes, the rest can usually manage to pick up the extra load.. For a while anyway The extra current they have to carry makes them all run hotter and eventually another one or two will pop. Once that happens, the alternator gets too weak to charge the battery.

It will happen eventually. It depends how much load you're putting on the battery. AC and headlights will accellerate things... You might go a few months, or you might have a few days. I'd replace the alternator ASAP so you don't get left on the side of the road somewhere, or have the car not start some time when you need it.

If you're handy, you can just buy an alternator kit and replace the brushes, bearings and diode pack. (Much cheaper than a rebuilt, It's not a terrbily hard task, but it takes a bit of knowhow and a few special tools.

quote Originally posted by Poncho Jim: a few special tools.

straightened paper clip

Batteries don't like alternating current, the overheating can cause your battery to boil over (VERY MESSY)

I think you should buy the rebuild kit as soon as possible as lurker says it is probably more difficult to get the alternator onto the workbench than to install the kit.

Good luck with this

There's a couple ways to r&r. I've found from under is a little easier. Remove the lower bolt and remove the belt. Disconnect the terminals and remove the upper bolt. It is a bit heavy and awkward to pull out but it almost drops on its own. It's helpful to have an extra pair of hands when lifting it back in.

Check around. You might find a place that rebuilds them locally. these places are usually cheaper than the autopart stores and you give them your old one as a core for them to rebuild and resell. They might even be able to custom build a higher output one for you.

common problem in 80's GM vehicles but mine usually went out in other 80's gm because of jump starting or a bad battery charger.

Taking off Fiero's alternator IS NOT NICE THING TO DO!

When I rebuild my engine I had my friend to rebuild the alternator. He did one mistake, put two insulated bolts to wrong place. Result: it will not charge at all. What I learned was that it is impossible to take alternator out without some major disassembling. It will not drop down or come out behind the wheel. Taking off dogbone might be answer but I know I can't get dogbone back together without mocing cradle. I disassembled manifold and heat shield. It was still very close call and took 3-4 hours. I don't know if manual transmission would help this job. Good luck anyway.

Here's what you will find. Red crosses are where insulators should not be.

Since your car is a stick, replacing the alternator shouldn't be too horrible. It'll help if you have an extra person.
Automatics are a PITA. Due to the size of the automatic, the alternator has to come out through the wheel well.

1. Disconnect the battery.
2. Disconnect the wiring from the back of the alternator. One plug and one lug.
3. Remove the bottom bolt.
4. Remove the top bolt. (This has always been "fun" when I've done it. It's usually very tight. Use a six point socket, and as much strength as you can muster. I've actually had to use an impact wrench to loosen one of mine. Once.)
5. The alternator should fall out the bottom of the car, past the axle. (This is where the helper comes in handy.)
Edit - If I am incorrect on this point, someone please corrrect me. Everything I own is automatic.
Edit 2 - You'll probably have to disconnect the toe link. 88s don't have them, so I overlooked that part.

Make sure that your replacement alternator has the correct pulley (correct number of grooves) and that the mounting lugs are oriented correctly (180 degrees apart. The 4 cylinder has the lugs 120 degrees apart.) The auto parts store should be able to swap pullies if the replacement is wrong.

6. As they say... assembly is the reverse of disassembly.

When you run the bolts in, don't tighten them completely. Keep reading.
Your 88 coupe had a tensioner. Made belt removal and replacement relatively easy. The V6 has no tensioner. You'll have to pry against the alternator and bracket to tension the belt, while tightening the bottom bolt. (This *is* nearly as complicated as it sounds. It's like trying to gift wrap a pile of jello. You'll see what I mean. Once again, a helper is useful.) Once that is done, then tighten up the top bolt, hook up the wires, and hook up the battery.

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Raydar
88 Formula IMSA Fasback.............................. 88 3.4 coupe................................................

Praise the Lowered! Read Nealz Nuze!

[This message has been edited by Raydar (edited 04-04-2006).]

I just removed mine on Sunday. We unscrewed the brackets and then took off the rear tire and then loosened the tie rod. It wasnt an easy job.

quote Originally posted by lurker: straightened paper clip

Yes, a paper clip works great for holding the brushes. (The last kit I bought had a stiff piece of wire included)

But you also need a set of reverse torx sockets to undo the case bolts. It really helps to have an impact wrench to remove the pulley nut and sometimes you need a bearing puller (depending on how bad the front bearing is siezed to the shaft)....

quote Originally posted by lurker: straightened paper clip

I use a toothpick...

Hi, Don`t you have to take the tie rod off? ( I did) Also with all the electrical up grades you`ll be doing , don`t most folks up-grade to the 88 alt ??

Wheres the best place to find a rebuild kit? the ones Ive found are like $50, so the reman is only like $20, definitely worth the warranty. Im looking for one for a 90 TGP or 92 TDC, and the both seem about the same

quote Originally posted by 3800superfast: Hi, Don`t you have to take the tie rod off? ( I did) Also with all the electrical up grades you`ll be doing , don`t most folks up-grade to the 88 alt ??

You're probably right about removing the tie rod (toe link).

88s don't have those, so of course I didn't think about them.

Replacing the alt on an 87GT with 5 speed was a piece of cake. It drops right out the bottom. no need to pull suspension or anything. now, the autos are a different story

quote Originally posted by Poncho Jim: It really helps to have an impact wrench to remove the pulley nut and sometimes you need a bearing puller (depending on how bad the front bearing is siezed to the shaft)....

BFHammer, couple of wood blocks and an old socket worked for me.

[This message has been edited by lurker (edited 04-05-2006).]

Okay. Back from the trip.

Thanks again for all the help. I've got an '86 V6 automatic. Does that mean that changing the alternator is going to be a PITA more than usual?

I changed it on my 4cyl '88 auto coupe and all I had to do was remove the rear passenger tire to get it out.

What do I have to do differently to change the alternator on the '86 V6 auto? (I decided to just buy a rebuilt alternator instead of trying to do it myself. I'm not sure I'm ready for rebuilding engine parts myself yet. Gotta take baby steps. )

Thanks guys! (Now I just have to find somewhere to work on the car to be able to do this. )

~Tress

You will have to take the tire off, pop the tie rod off the knuckle, unbolt the alternator, and the alternator bracket, and wiggle it out of there. It only took me like 30 min last time, but Ive done it a few times