Alternator Situation
Freshman User
Joined: May 2010
Posts: 45
Likes: 0
Weird - posted a reply, but it disappeared?
Anyway, I've been driving about and so far the voltage is holding at about 12.5-12.7 volts. Oddly there is not jump in voltage when the truck is running to indicate the alt is charging, but it seems to be holding and maintaining charge.
Anyway, I've been driving about and so far the voltage is holding at about 12.5-12.7 volts. Oddly there is not jump in voltage when the truck is running to indicate the alt is charging, but it seems to be holding and maintaining charge.
Freshman User
Joined: May 2010
Posts: 45
Likes: 0
I have been measuring on the battery, but I just went out and checked on the post on the starter relay that goes to the alternator (I think that is what you mean by "alternator battery post"?). Anyway I am getting the same reading there. I have driven a good 50-60 plus miles with probably two dozen or more starts and no run down on the battery, so I must be doing the charge test wrong(?).
More Turbo
Joined: Jun 2015
Posts: 534
Likes: 27
From: North Texas
Put the Multimeter negative on the battery negative post and put the Multimeter positive on the Alternator post (that has the cable running to the starter relay) and you should see 13.7-14.4 volts with the engine running, anything less and you're not charging the battery. Likely the alternator will pass a bench test but still isn't producing enough volts to get the job done.
Freshman User
Joined: May 2010
Posts: 45
Likes: 0
So I got it fixed and the issue was not what I would have expected. After going over everything and replacing some of the wiring and fusible link the issue was fixed by replacing the crumbling plastic instrument panel mounting gauge. Go figure. Running a strong 14v ever since and can finally use my lights lol.
More Turbo
Joined: Jun 2015
Posts: 534
Likes: 27
From: North Texas
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Lead Driver
Joined: Jul 2017
Posts: 9,609
Likes: 1,179
From: San Jose, CA
Did a whole write-up to see if I could help, then noticed the next page and see you got it fixed! Glad to hear.
not sure what a plastic plate in the dash would have had to do with it, but the results are the results. Glad it's working.
On a side note though, what about all the main grounds? Since this is an engine swap (and by a PO to boot!) are all the original grounds that would have been on a '79 still present?
The main cable should go directly to the engine block. Just about anywhere is acceptable, but closer to the starter motor you can get it is a little "better" to my mind.
There should be a ground from the battery to the body too, usually at the fender. I add larger ones and attach them to one of the starter relay bolts, but just about anywhere is good.
And due to the swap, the main reason I brought his all up is that there would have been a braided strap bolted between the back of the intake manifold and the firewall. I think this one is very important and they get removed a lot of times and not put back when engine swaps take place.
So just some other things to think about while you're bringing your truck back to peak condition.
Paul
not sure what a plastic plate in the dash would have had to do with it, but the results are the results. Glad it's working.
On a side note though, what about all the main grounds? Since this is an engine swap (and by a PO to boot!) are all the original grounds that would have been on a '79 still present?
The main cable should go directly to the engine block. Just about anywhere is acceptable, but closer to the starter motor you can get it is a little "better" to my mind.
There should be a ground from the battery to the body too, usually at the fender. I add larger ones and attach them to one of the starter relay bolts, but just about anywhere is good.
And due to the swap, the main reason I brought his all up is that there would have been a braided strap bolted between the back of the intake manifold and the firewall. I think this one is very important and they get removed a lot of times and not put back when engine swaps take place.
So just some other things to think about while you're bringing your truck back to peak condition.
Paul
Thread
Thread Starter
Forum
Replies
Last Post
tyler.dunn94
1987 - 1996 F150 & Larger F-Series Trucks
4
Aug 6, 2017 08:03 PM
Walleye Hunter
1999 - 2003 7.3L Power Stroke Diesel
10
Jun 1, 2016 06:17 AM
NW 150
1973 - 1979 F-100 & Larger F-Series Trucks
5
May 7, 2015 08:25 PM
KIKKUP
1973 - 1979 F-100 & Larger F-Series Trucks
6
Oct 23, 2013 10:19 AM
jaspirr
1973 - 1979 F-100 & Larger F-Series Trucks
11
Aug 11, 2010 10:30 PM