Am curious if anyone knows whether you can replace a 125 amp alternator with the 200 amp high output alternator. The factory service manual says that the units are identical and use identical connectors, but just would like to hear from anyone if they've experienced this or heard of it being done. I know, the alternator going out on an 08 with only 58,000 miles on it is crappy. But Ive got crappy luck. My Optimas are charged, but the alternator is putting out only 12.6 volts... not enough to keep them charged AND run the accessories.

 

bump it up to keep it fresh.

 

Mine has the 200 amp as part of the snow plow package. Check pully size, if they are the same you are good.

 

Thanks for the bump Scott, and thanks for the pulley info. Ill be looking into that in the morning.

 

yeah I have the 200 amp as well, snow plow package. I don't plow buy I always buy it for the alternator and the front springs.

Never thought that maybe the pulley size might be different.

 

its unlikely that any of the externals on the alternator are different between versions.. its would cost ford a LOT of money to do that..

so this has to be an easy bolt up change...

I replaced the alternator on my daughters stang with a higher amp output and used same connectors and all..

so, altho I haven't seen one, I'm sure they are physically the same. and If it doesn't fit, I'll buy it off you and figure out how to do it on my 08!..

Sam

 

Thanks Sam. Thats why I love this forum. Great people here. Im hoping all goes well. According to the Service Manual everything's the same. Just hope the regulator will handle it. We'll see. One thing I am concerned about though is whether the alternator even needs testing. Ive heard you can test one by just putting a voltage tester on the battery and starting the engine. The voltage you see is the voltage output of the alternator. Anyone else heard this? It's on Optima's website. Just dont trust AutoZone or any other place to go hooking things up on the truck and shorting out the alternator, and dont have the time to go sit at Ford for a 65.00 test to tell me. Any ideas?

 

the regulator is internal..

if its used I'd take it to Autozone..

the only thing they didn't find on the 160 amp I put into my hotrod was a broken brush pickup that only failed at 10,000 alternator rpm.. the AZ test is at 4000 I think.. 10,000 rpm at the alternator was about 2400 engine rpm..

typical of the ford car alternators.. all the cop cars had the brushes fail as they took off at full throttle..

the alternator rebuild shop tested at 12,000 rpm. failed immediately.. and also when hot.. (exactly the symptoms I was seeing)..

sam

 

Good to know. Im starting to think I was told wrong by AutoZone. They tested my alternator and said it was bad. They said it was only putting out 12.5 v. The manual says it needs to be anywhere between 14.0 and 14.8. I just went out and tested it using the voltmeter on the jumper cables while she was running and it's putting out 14.3. Plus I dont have an idiot light. Now they simply did the same thing by only checking the voltage at the terminals while the truck was running. Is there another way to test it other than taking it to Ford and paying for it?

 

The one thing they can do is put it under load. That you cannot do with just a voltmeter.

If you go to napa they can do the same thing.

 

Thanks Scott. We have a NAPA here but they arent very customer friendly as far as coming out and helping troubleshoot things. I plan on just going to Ford I guess. The "not knowing" is starting to wear on me. Thanks for all your help.

 

Have you checked batterys?

 

using a voltmeter measure the batteries not running should be around 13v start the engine now it should read around 14v to put a load on the system turn on every thing in the truck ie headlights, heater, air, play with the p/s and p/w etc should show 14.4or higher if its not charging it will be 13v or less and be dropping hope this helps

 

Thanks Jim. Heres the thing. I replaced both batteries last March with two Optima Red Tops when everyone was getting the "Check Brake System" messages, and everything has been fine til last week. I was sick for a few days and didnt drive it. I go out one day and it starts, but I can tell the batteries are down. I put both batteries on charge for 24 hours and then took it to AutoZone, where I bought the batteries and had them load tested.

They said that they were fine but showed they needed charging. I told them they had been charging for a whole day. He says the Optimas take a long time to charge, but Optima says no, they take just the same amount of time as a regular battery. Talked to a Optima engineer. So I asked the AutoZone guy to check my alternator and he says you need a new alternator, only putting out 12.5v. So I get home and go through the Service Manual, and it states a good way to do a quick check is to put a voltmeter on the battery and while shes running turn on lights, radio, A/C, and anything else you can and check the voltage at the terminals. If youve got between 14.0 and 14.8 youre fine.

Well I had 14.3, so I figure the AutoZone guy was wrong. So I go to check the batteries again after driving it, and they are back down to 12.3 , Called Optima again and they said that even though the batteries passed a load test they may be sulfated, and therefore might not hold a charge well, even though they pass a load test. They want me to go get a readout from a load test and call them back. But more than the batteries, Im worried whether the alternator is TRULY ok.

I mean after driving it I shouldnt come back and put the volt meter on them and get 12.4 should I? Seems like if they're charged for over 24 hrs and they were at 12.8 when I pulled them off why would they be down that much after driving for over an hour if my alternator is truly not bad? Im sick of this...... if its not the black tail pipes its the alternator. Sorry, just blowing steam here...... Senix knows what Im going through

 

yup, wish I could take that truck and work it over for you...I'd make it sweat