BLDTruth

I'm in the process of doing an alternator/battery cable/charge cable upgrade - is there any reason you cannot run a charging cable from the alternator directly to the battery? The factory wire runs to the fender mounted starter solenoid. I am upgrading to a 4 gauge cable with fusible link. Been awhile since physics class so I thought I would ask before blowing things up.

Chris_1

iTrader: (1)

Straight to the battery is fine. The connector on the side of the fender solenoid is just used as a junction block - so you don't have too many wires at the battery connection presumably. But it already does go straight to the battery, basically; it connects directly to the power wire that connects directly to the battery. Your connection that bypasses the solenoid junction block will be fine.

BLDTruth

^^^Figured as much but glad to hear you say it too

Steve83

Connecting at the starter relay is more reliable because it's not as close to the acid. The battery terminals are designed for some exposure to acid - the alternator output cable's terminals aren't. If you clean all the rings on the relay, and apply a little electrical grease (not dielectric, or chassis, or thermal, or anti-seize, or battery snot) to each one, you'll have a longer-lasting connection that performs exactly as well.


(phone app link)

BLDTruth

Well I got everything buttoned up today. New 130 amp alternator, 1/0 battery cables, 4 gauge charging cable, military terminals, etc.

Only problem I have is that the voltage gauge is reading low. Like 10v instead of the usual 14 when it is running. This has caused the battery light to light up. I double checked all of my connections and let it run for awhile to see if it would die. Shut it off and started up a few times and it cranked like a rape ape. Took it for a spin around the block and it drove great.

I need to check the voltage on the terminals while it is running (buddy has my DMM), but I am suspecting the new TYC alternator has a buggy voltage regulator. I was wondering if I could take the old one off my 95 amp original motorcraft alternator and just slap it on there and see if it solves the problem.

Chris_1

iTrader: (1)

Sounds like a good way to end up with 2 alternators that don't work and no warranty on the new one maybe.
I would get my meter back and verify actual voltage.

BLDTruth

Yeah everything is getting tested before I do anything else - the fact that the truck started 3-4 times without problems, and ran like normal, suggests to me it is not a problem with the charging system itself and more a way that the new alternator is talking with the gauge. But electrical stuff is fairly new to me and I am not going to take any more chances until I verify a few things.

Steve83

The alternator doesn't "send" the voltage to the gauge; the gauge simply displays the voltage it's exposed to, from any source. If the gauge shows ~10, then it's probably getting ~10 at that moment. If it goes up when the key is OFF, you can be sure the alternator isn't working.

This caption explains how to test any 3G:


(phone app link)

If the test makes the voltage go high, that means the alt itself works, and the VR isn't turning on for some reason. Double-check all the wiring, and if that's good, swap VRs. But this is why I recommend finding a nice JY 130A 3G instead of a fresh reman. It's very UNlikely that a truck would go to the JY for a bad alt, or that it would keep running long enough to wreck with a bad alt, so JY alts are almost always still working. Especially the fresh remans which are much cheaper at the JY.

BLDTruth

Voltage gauge is rock steady, both KOEO and KOER. You know how when you turn your lights on or put some other stress on the electrical system the voltage gauge might flutter a little bit? Doesn't even do that.

Hypothetically, would the truck even start at 10-ish volts? And would it start 3 times in a 5 minute span if the alternator wasn't working?

I know, I know, I need to test and probably can't do anything about it til tomorrow....just trying to narrow it down.

Chris_1

iTrader: (1)

As long as the battery has enough juice in it, it will start and run even if it's not charging. Eventually you'll use up the power in the battery and it has to be recharged.
If you check with a multimeter (set at 20 volts dc) across the battery terminals you'll see battery voltage (usually about 12.5 if it's charged) then when it's running 14.6 or so means it's charging.
If you're not getting a charge you can move the positive test lead to different points back up that line all the way to the nut on the back of the alternator to see if power is coming out of the alternator and if it's getting through the wires and connections.
If it's an event to get your meter back one of those 15.00 cheapies will work well enough to figure out what's going on.
If your headlights are dim because the battery is low, revving it up should make them go bright if your alternator is working.