Auto Mechanic types: Please help me replace my alternator

Lately, the the little-red-battery-icon-with-“AMP”-underneath warning light on my 1991 Ford Tempo’s dashboard has been lighting; it will light for a few minutes – usually while I’m sitting in traffic – then go dark.

It’s begun to do it A LOT recently, so during a routine inspection and oil change, I asked my regular mechanic (who I trust) to look into it. He called me back to say I needed a new alternator – a $180 (aprox) job. Money is tight and I’m a pretty handy guy, so I told him to leave the old one in place and I’d replace it myself.


Okay. Is this something your average homehandymankindaguy can handle? Can I just stroll into Pep Boys, ask for an new alternator and hook it up in an hour or two with just a set of socket wrenches and a screwdriver?

If so, here are some more specific Qs:

  1. If there’s more to this job than just plucking out the old one and screwing in the new one, is there a website/manual that could walk me through the exact procedure?

  2. A fast glance at a JC Whitney catalog tells me that a replacement alternator for my 1991 Tempo is the SECOND MOST EXPENSIVE one in their inventory – a hundred bucks! (Versus, say, thirty-five smackers for some Dodge replacements. WTF!!!) Is this the kind of part I could try to get USED at a local junk shop? Or is a used alernator a pig-in-the-poke that’s not worth the gamble of getting stuck with a bad one. If I opt for new, where’s a good – but cheap – place to buy it. Not a Ford dealership, I presume.

  3. Also, what’s the mystique with alernators? JC Whitney wants the year, make, model #, stock #, blah, blah, blah of the old one before they’ll sell you a replacement. What’s with that???

In closing, I should mention that this is a 10-year-old car that I use for basic transportation, not to substitute for the child I never had. I want to keep it running and happy, but I also want to preserve my budget for more important things, like food. So please keep that in mind as you dole out the advice.

Thanks a whole bunch in advance.

If you are reasonably handy with your tools, there is no reason you can’t do this job yourself in a couple of hours, assuming you can get at the alternator relatively easily. The very first thing you want to do, and this is quite important, is disconnect the battery.

The alternator will be on some type of a swinging, or sliding, bracket that is used to tension the belt. (Although some cars have a separate screw-type tensioner on an idler pulley. These make re-tensioning a snap.) Your first step is to loosen the bolt that allows you to release the tension on the belt, so you can remove the belt itself. A potential complication must be mentioned here. If your car has more than one belt, and the alternator is not the “front” one, you’ll have to remove any others that are in front of it, too. (By the way, you should replace any belts you have to remove at this time.)

Then you should carefully detach the electrical connections, making sure you know which terminal to they should be reattached to. Then you can remove the alternator itself. It should only be one more bolt.

Reassemble in reverse order, obviously. If your car is not equipped with the screw-type tensioner described above, re-tensioning can be a bit of a problem. You’ll want some type of lever to provide a mechanical advantage, or perhaps, someone to help you with this step. Make sure, if you had to remove more than one belt, to put them back on in the correct order.

Now, addressing your other concerns. You can buy your alternator at most any auto supply place. Call around and get the best price/warranty. They’ll tell about “core charges,” which are simply a deposit you make until you bring the old alternator back to them. Alternators can usually be repaired by replacing the brushes and rewinding them. That’s why they want your old one.

The model you need is more expensive than many others because it probably has an internal voltage regulator. The old Chryslers have an external regulator. J.C. Whitney is asking for all that info because the required output of an alternator can vary greatly with the demand placed on it. Air conditioning and what have you. Also, some cars have an option called a “heavy duty” electrical system. The alternator for these systems obviously is built to provide more electrical power. Also, they don’t want to ship you the wrong one. Most automotive parts stores will not accept returns on electrical components since they be damaged internally by the consumer. They do not want to accept defective goods in exchange.

I think that about covers it. This isn’t too tough a job. Good luck and have yourself a knuckle-scrapin’ good time.

I’m not exactly Mr. Goodwrench, but I’ve stuck in a couple of alternators and may be able to be of some use here.

I’d go to a parts store and get a rebuilt one. Generally quite a bit cheaper than new, but you still have a pretty good idea what you’re getting.

Probably not a really bad idea to disconnect your battery before taking the old one out. Taking it out and putting the new one in will probably either be fairly easy, or else near impossible. Depends primarily on where Ford decided to mount it. Usually they’re up high so they stay dry, and thus one of the easier things to get at. I’ve only been involved with two that were pretty tough, and they were on a Dodge Charger and a Toyota pick-up.

Another option that would probably be even cheaper if you can get by without the car for a day or two is to pull the old one out and have it repaired. Any shop specializing in auto-electric should be able to take care of it for you.

Good luck.

I’ll add my $0.02 to a few of UncleBeer’s statements based on my experience changing the alternator on my piece-of-shit Grand Am.

My lever was the open end of the wrench that fit the tension wheel bolt crammed into the closed end of another large wrench (i.e. a two-wrench assembly), and wedged in such a manner so that the two components moved as one. Not the safest method, I know; you may want to invest in a breaker-bar, if you don’t have one already. I did need a friend to take the belt off (and put back on) the alternator wheel while I held the tension wheel loose.

Also, when you’re at the store, check the wheel on the new alternator to make sure it has the same number of teeth as the wheel on the old one. If not–no problem–they can just switch out the two wheels. Also, make sure the electrical post on the new alternator is in the same position as on the old one; they may need to “clock” it. You probably know this, but when you’re calling around and they tell you they have one alternator in stock (or any auto part, for that matter), tell them to check the shelf. More often than not, around here anyway, when the computer says they have one in stock, they are out of stock.

And definitely disconnect your battery when doing this–at least the negative terminal.

Oh, and can we move this to GQ so I can get some posting credit there? I’ve fallen quite short in that forum lately.

Piece of cake. 2 years ago, I replaced my alternator by the side of Rt 1 10 miles inside the PA border when the old one broke and the battery ran dry. Called my Ex (then current) Wife, told her to bring my box, socket and Allen wrenches and to bux “X” type alternation, and did her right by the side of the road. Easy as pie.

The job, not my wife. Sheeesh, I gotta think more about how I put things!

I know nothing about alternators, but I must say, Dave, that is freakin’ hysterical! :smiley:

Change the brushes and reinstall the alternator to see if it works first. Replacement brushes are dirt cheap and are often the cause of alternator problems. I’m nowhere near an “Auto Mechanic type” and I’ve done it. Good luck.

First thing you can do is call up your local junk yard and get a used alternator. A couple of my past cars were repaired mostly through junk yard parts that lasted forever, with the exception of carburetors. A $200 alternator can cost you only $50. You can also remove yours and take it into a shop to be rebuilt at a fraction of the cost of a new one, which is probably going to be a reconditioned, used one anyhow, just cleaned up to look new.

Then, replace it the same way you remove it. The hardest part is adjusting the tension of the belt because too loose and it will not work right and too tight and you’ll burn out the bearings. You should be able to remove it within 30 minutes or less being inexperienced, and take about the same time putting one in.

You might need a screwdriver to work the wiring plug out of it’s socket and pay attention too how it went in.

As others have mentioned, absolutely.

In fact, I replaced the alternator (several times, actually) on my 1988 Tempo. The first time was in the parking lot of my local auto parts store (the bearings siezed, threw the belt. I got there on battery reserve, but there was no way I was going to drive someplace else to fix it).

The '88 might be close enough to the '91 that some of my observations might help. I recall that the bolt the alternator pivots on was somewhat difficult to remove. The mounting bracket required a extension for the socket, but that forced the wrench into the radiator overflow bottle. I had to loosen the bolt at a slight angle until I could remove it by hand. As others have mentioned, it’s helpful to have a lever of some kind to position the new alternator in order to install it with the correct belt tension.

The second time I replaced the alternator (after the friendly road-side assistance driver shorted his jumper cables across the alternator),the replacement I picked up was assembled incorrectly. It looked right at first glance, but one half was rotated 120 degrees relative to the other. When I went back to get a good one, the new one failed the bench test. I ended up having to go to another store. So make sure the replacement is “clocked” correctly, and make sure the store bench tests it before you leave the store.

I went with a rebuilt alternator, that worked fine until the aforementioned run-in with the roadside assistance guy. But I was able to get a free replacement because the first came with a lifetime warantee.

I was told that the alternator for my Tempo was so much more expensive because it had a built in dohickey (regulator?, rectifier?), while most others had them separate. Don’t know if this is true. It came from the roadside assistance guy :-).

**WHO DA MAN?!?!


Yessiree, Bob. Thanks to all you wonderful Dopers I’m back on the road. But, not without an adventure, I should add.

I located a used parts dealer (read: junkyard) in the Bronx who said he was certain he had what I needed, but he would have to see the original alternator so that he could give me an exact match. Cost: $35. Okeedokee by me I told him. (Remember, this was used, not rebuilt – but, hey I’m willing to gamble on these things).

Trouble is, as I drove up there I noticed that just about everything electrical is beginning to fade – slooooow blinkers, sloooow wipers, diiiiiim headlights. So, I surmise that my bettery is losing every last ounce of juice it once had.

So, I get to the dealer and leave the engine running. He sizes up my alternator, and sure enough, he hands me an exact match for 35 smackers. So far so good. I put it in the trunk with the intention of doing the swap at home.

But my car has stopped. No problem – he gives me a boost. Okay, I head home. But at a light the car dies again! Ugh. I call AAA and get another boost. I drive about 10 blocks and it dies AGAIN!

So I left it parked by a curb (legally), took the subway home, piled a bunch of tools onto my motorcycle, headed back to the Bronx where the car was parked, and replaced the bad alternator with my newly-bought replacement.

Of course, I followed all your wonderful tips, too. I boosted the battery with my bike’s battery and she (the car) ran like a top.

No dead battery. No red dashboard light. And $150 saved!!!

So again, thanks for everybody’s help. Couldn’t have done it without you!

Looks like you did her by the side of the road, too. :smiley:

I had an old Escort that I used to tool around in. The alternator died on the highway one night, and the battery lasted just long enough to get to a friend’s house. I stayed the night, and he took me into town the next day to get a new one. We got back to his house, and I started farting around, cuz I didn’t want to fix the damn thing. We were supposed to go do something that day, don’t remember what, so he was in a hurry. Finally, he got tired of my putting it off and said “Tim, you have 20 minutes to change that alternator or I’m gonna kick your ass.” I told him to time me.

Got it done in eight.


Might just be an alternator belt. Did you look at it? Is it shiny? Get a new one. Get a new one even if you get a new alternator.

Oh, get the book on the car by Hayes, about $17.00 its gives you instructions!

Also, do disconnect the battery first.

I’ll just add one little post script since things worked out really well.

Get your battery checked to make sure it is functioning properly. If it isn’t charging properly it can draw too much juice from the alternator and cause it to burn out.

I just went through this scenario with my van so had to replace both the battery and alternator.