My 97, with 88000K now has a wierd problem.

When I start to rev it up, my alternator light blinks (flickers) when I get over 4K rpm.

I thought that maybe the belt was slipping so I bought a new one. The old one is exactly the same size as the new one and is in perfect condition, ie. no cracks and such...

While the belt was off, I turned the alternator by hand and I feel some grinding (not smooth) so I figure that the bearings are going bad.

I did not replace the belt, but I may go get another one just to be safe...

Any ideas?

A new 95amp one is $180.00 and a 130amp is $130. I know that seems strange..and I have not figured out which one my truck has.

If my truck has the 95 amp, can I put the 130 on it?

 

I had a similar problem once. After the first place told me I needed a new alternator, I went somewhere else for a second opinion. It turned out to be a burnt wire that cost $2.00 to fix. Check all the connections first before you get a new one. And yes, you can put a larger alternator as a replacement.

 

Thanks for the reply. I will check...and see what happens.

 

While talking to a Ford Mechanic (my relative) about the missing tow package equipment on my 2001 SuperCrew he said his dealer did not know how to identify one alternator from the other. He said they usually go by how much extra equpment came with the truck - is it a Lariat, does it have power windows, AC, power seats, factory trailer package, or a special radio package? If it is well equipped electrically then they put the bigger alternator on. If it doesn't have all the extra electrical do-dads, then you don't need it. Hope it helps.

Other things to think about - 130 amps is a lot more than 95 - try comparing the wire sizes on the alternators. I would expect the ground and power wires on the 130 to be bigger. Also, if your truck was equipped with the 95 it might be fused for 95 amps in which case a 130 may not do you any good. A wiring diagram should show if any fuses or fusible links are in the path between the alternator and the battery.

I hope you give the dealer grief about Ford not having identifying marks on the alternator. It means that we the customer have to guess at the proper size. Very shoddy quality on the part of FoMoCo.

 

Do you pronounce your city as "Plane Oh" or "Plan Zero"? OK... local joke.

As to alternators, according to the 2001 source book, ALL F150's come with the same size alternator, namely 130 amps. And yes, the wire from the alternator is as thick as a battery cable.

FWIW. 130 amps x 12 volts = 1560 watts. 750 watts = 1 HP, so assuming a 50 percent efficiency for the alternator, it takes about 4 HP to generate maximum output.

Of course, I'd like to know the RPM's for 130 amps.

 

While at Advance Auto, buying two new rotors for my front brakes, I asked the alternator question.

He told me the same thing about electrical load.

Since I have a fully loaded XLT, electrical everthing, I am going to assume I have a 130amp alt.

They also told me if my battery is weak, I could see the same thing. They will do a electrical check for me for free, when I go back tomarrow when I have to go pick up the rear drums.

 

Sorry. I didn't mean to say that I think that you need a new alternator just yet unles maybe the bearings are bad. I don't think that slightly bad bearings should cause the idiot light to flash. I like the idea of checking for loose wires - maybe the engine shakes more at 4k rpm? Check the voltage regulator also.

You can check a basic alternator and regulator operation this way: Get a voltmeter and check the battery voltage with the engine and ignition off - a charged car battery should read between 12 and 12.5 volts (DC). Clear the voltmeter leads from the fan blade and start the truck. While running, the battery voltage should now be higher - somewhere between 13 and 14.5 volts. Put a load on the system by turning on your headlights and turning your heater or vent fan to high. This loads the electrical system by 12-20 amps. The battery voltage might drop a bit (0.2 - 0.3 Volts) but should still read very close to the last number. The higher Voltage reading while running and running with a load indicates that both the alternator and the voltage regulator are working (charging). A reading over 15 Volts may indicate that the voltage regulator is bad (check meter readings against another car to verify that the voltmeter is reliable) and is overcharging the battery but that is kind of rare and usually results in a failed battery. With the electrical load on, slowly bring the engine reves up and watch the Voltage closely. The Voltage should stay fairly steady from 1200 rpm and up. If your Voltage starts jumping around at 4k rpm I would try varying the load and seeing if that made a difference - don't know what that would tell you but it might be fun. If it jumps around at higher revs I would suspect wires, then the regulator, then alternator, then a computer-regulator(?) link. By the way, if you find that the system is not charging at all, its often hard to tell if it is the regulator or the alternator. Most mechanic/battery shops have a machine that can tell if it is the alternator or the regulator and should check them for free if you buy the offending part there. Rebuilt alternators are usually a good buy - all that goes wrong is a bearing and a few diodes and they get replaced in a rebuild. Good Luck

 

I work at Advance and see things like this all the time. There is some good advice on here so far. If all Advanced stores are the same and they should be fairly close. They will use a rollout Arbst or Bear tester. First you can hook your battery up with the truck off, hook cables, input cca's of battery into tester and tester will test for about 50 seconds. During this time the tester will put the batt under a heavy load ( I have seen this tester completly discharge a low charge batt in nothing flat). While it is testing you can watch the volt guage on the tester and usually when it is first connected you should have around 12 (+/- 1 volt). Under load I would like to see no less than 10 volts. If batt is weak the machine will ask you to recharge and test again. Advance then can usually take your batt out and charge it full in about 30 minutes for free (the inside charger will test the batt too). Then in the alt test with the rollout they will hook the cables to the batt and then hook a sensor probe to the negative cable including that little black wire that runs too the neg side of batt. They will then input engine size and ask you to start the vehicle. Then they will ask you to rev the truck up to 2000 RPMS and maitain that for 10 seconds, then they will ask you to let it idle down and run for a few more seconds. When the test is complete they should give you the peak output voltage, peak amps, and diode condition. I am not positive on this but I would say after about that 2 grand mark you are not going to see any more charging abilty from the alt, you might even start to lose a few amps of charging. It might be wise to check out you alt and batt cables very closely. Seems like the batt cables on these Fords have tendency to corrode, sometimes from the inside out. So the is a possibilty it can be corroded half down the cable and you never see it because of the insulation on the wire. You can install the higer amp alt and no harm will ever come but I always try to figure out what is on the car and put the same type/size back on.

 

This is some good advice from the other people...sounds like you are losing the amperage at high revs....the slipped belt was a good idea...If you are decent mechanic you could crack the alt open and replace the brushes and save you some money...plus you still have your alt instead of someones elses headache...

You should be able with a voltmeter and rev engine see if it maintains 14 V's...

I always like to repair my own alt/starters..they are easy...

The worst it could be would be the diodes and you can replace them...If the fields are bad then get a rebuilt one...

I have seen ones that had the voltage but not the amperage...