7.3 idi charging 18v at idle

[laserjock]

15 posts and no one has said 3g swap it. Must be a record!

 

[pelky350]

I've considered a 3G swap but since then I have already redone mostly all my starting and charging system and switched to all led lights heaDlights included. I have power nothing and a 5 speed. Very little electrical load only when heater fan is on high do I see a voltage drop so I haven't had a need for a higher output alternator really

 

[BeastMaster]

Just drove the truck around town and checked the voltage again when I got home, it's bouncing from .6V to 13v, then up to 17v again In a matter of seconds. Going up and down like that over and over again

From the photo you posted, looks like you are measuring directly across the battery...

Something is really weird going on here... your *battery* flat cannot change voltage from ".6V to 13v, then up to 17v again In a matter of seconds."

It sure looks to me like you have a bad connection somewhere at your meter.

How about any light bulbs you have on your truck? Did you burn out turn signals or other indicators? If you turn your headlights on, are they brighter/dimmer than normal?

Being you said your truck is 1985 vintage... I am assuming you still are running old-school incandescent headlamps? You know by now exactly how bright those things should be. I know I can "see" my glow-plug controller operating by how bright my headlamps are. ( Actually, when I first got this beast, I thought he had a short somewhere... it wasn't until later I discovered the erratic power fluctuations on the battery were just the glow plug controller ).


Make damn sure that voltage regulator is truly grounded... Not just any bolt. That "ground" sets the output voltage. If your "ground" is above battery ground by, say, three volts, the regulator will put out three volts too much. If in doubt, find out where your regulator ground wiring goes, and see if there is *any* voltage between that "ground" and the battery negative post.

I had a car once fool me that way... the "ground" was connected to the engine block, and the battery negative was connected to the vehicle frame. Over time, the bolts corroded or whatever, and looked like the current no longer went through the engine mount bolts, and instead seemed like it had found a path through the transmission. Caused the whole starting system to be really flakey. The rubber engine mounts didn't help the power flow much. Maybe at one time there was a cable for that purpose... to ground the engine to the frame... but could not find one. I put one in and the problem went away. You know.. big heavy welding-cable kinda wire. IIRC, I used an old butchered jumper cable with some copper tubing I made end lugs out of, and attached one end at the starter motor mount, and the other end right where my battery negative was grounded at the vehicle frame under the hood.

 

[Thewespaul]

Pretty sure the 3g alt puts out less amps than the ambulance package alt...

 

[icanfixall]

Sounds like your alternator is working but the regulator is not modding the voltage. I suggest you replace the regulator but...Make sure you disconnect the batteries from the electrical system first. then once the regulator is installed reconnect the batteries. Years ago I replace the regulator TWICE because it burned out the first time. My mom n pop shop told me to install the regulator on a non entergised electrical system. It worked fine too.

 

[DaveBen]

Make sure your grounds are CLEAN and tight. Bad grounds cause the most problems.

 

[typ4]

Is your alternator a 1g Ford? Download a Ford wiring diagram for alternator and check every one before you burn up your truck. I'll add more tomorrow.