The following is from an earlier post, so to be rather blunt it makes giving advice a little precarious at times ....

"I have an amp gauge and the gauge isn't fluctuating. It's almost in the center where it's supposed to be at, It doesn't fluctuate at all. "

I'll stand behind other's comments that new or rebuilt does not necessarily mean good, you have to test and verify what your truck is doing compared to what is expected. You need to get some direct amperage readings at different RPM levels. Electrical gremlins sometimes can be tough, but you have to methodically track and rule things out, or hire someone who can do this for you. Sure, the simple one's you most certainly want to do yourself if you are able. I gave you some suggestions for some items that were more advanced issues, assuming you have ruled out the other basic items, hope you get to that point soon .....

Cheers .....

 

I will add an important piece of advice i recently read that was posted by the member Old Paint:

All the electronics on this truck are a massive system. Its not just the alternator pumping electricity to everything through a couple wires. (obviously right, but that's the point)

You have several wires and several more connections, as well as fuses (two connections per fuse) and fusable links and releys that could potentially cause an electrical issue. All of wich add resistance to the electricity under normal conditions, so add just one corroded connector in the chain and its a recipe for gremlins!

It goes Alternator->starter relay->distribution panel->fuse box->then finally to your guages->then it has to properly ground to the cab, and the cab back to the negative post.

A break or corrosion at ANY point can cause issues.

One of the most important connections of all is the post on the starter solenoid with all the ring wire connectors on it. So many things are powered from that point. Double check, clean, and contact grease/antisieze that connection as well as the solenoids connection to the side of the engine bay.

Like I said before, it may just be a bad alt, but all this should be checked just as preventative maintenance on a truck of this vintage.

Good luck and Merry Christmas!!

 

So if it was the tensioner wouldn't I hear a squeal from the belt if it was slipping? If so I don't seem to have this problem. Seems like I'm going to have to strip the whole harness and I may have to look for the problem that way but not looking forward to that

 

Typically you will hear a squeal.

I wouldnt strip the harness neccesarily. You should be able to clean and grease the connections with it in the truck. Most of the cab electrical issue threads here seem to end with a problem getting power to the cab or grounding back from the cab.

These trucks have dealt with so much road salt over the years its no wonder. Thats why i always liberally grease cleaned exposed connections and grounds with anti-sieze (conductive), and fill sealed clip on connectors with die-electric/silicon grease.

Hopefully after you hit some of the usual suspect connections/grounds you will have good news to report back!

 

Check all of the alternator connections and battery connections, after that test or get tested the alternator output. Come back with real numbers and someone here will figure it out for you.

 

When it happen on mine no the belt didn't make a sound, was working fine then one morning fired it up to plow to notice the voltage was low.

Had to clear lots so off I went after noticing that the second i gave it a little gas it was in fact charging. Sure I looked it over a minute but couldn't find a bad connection or anything obviously wrong with it and at first figured the alt was throwing in the towel, no I didn't check the belt it didn't make a sound.

I had a couple of lots to clear first so I proceeded to do so, it was only when the steering assist dropped out at idle did it dawn on me what as happening that the accessory belt was slipping. Nothing else wrong just the belt slipping.

The belt didn't make any noise so my first assumption was that it wasn't the problem and at least up until that moment, until then I had full power steering all the time up till then was normal driving or clearing snow in straight line going back and forth style.


Again I'm not saying that is for sure your problem, I'm only stating it exactly matches my trucks symptoms of a slipping belt.

What I am suggesting is that you make sure that your belt is not wore out, that it is tight that your tensioner is working 100% of its operating range, that you take a minute and make sure it is not the cause of your troubles.

Doesn't sound like you've done anything to rule that out.

Keep in mind my tensioner worked just not to its full range as when "new", once the belt wore down just beyond the tensioners usable range to keep it tight the belt slipped on the alternators pulley, there by causing the amp reading to rise and fall dependent on idle speed/just above idle speeds.

But hey if you don't want to take a minute and check the accessory drive system? even though you clearly have no clue what the problem is?

don't....

 

Ok, I see everybody talking about a amp gauge. These years trucks never had the amp gauge only the 86 and older ones do. A 95 truck is a voltage gauge and is not a most accurate one too.

Best to check with a good volt meter at the battery to see how much charging voltage is going to the battery at various RPMs . The plug in volt meter(shown in photo) ones are good but can show a voltage drop as in my case with the 89 F250. For charging issues it best to check right at the battery.

Most likely is the belt slipping as others have said. 2nd problem is bad grounds from the CAB TO CHASSIS/battery ground post. 3rd problem is probably a bad connection along the power feeds going from battery to power box,bulkhead connectors and various circuits. That will be the most PITA to find(like what is occurring with my 89 F250) as you will have to meter out where the voltage drop is occurring.

 

Eddie makes a good point.


Also, I don't think we have established whether the apparent voltage drop is actually NORMAL, or truly dropping low enough to start causing a problem through draining the battery.


The more accessories turned on, the less voltage available to charge the battery, but it only becomes a problem when the voltage going to the battery approaches what, 13 volts? The dropping of the gauge may not indicate a true drop of voltage to a bad level. So while the blower motor slowing down may be an annoyance, its not truly a problem unless the battery is simultaneously being drained.


Here is an excellent thread on this same subject:
https://www.ford-trucks.com/forums/6...is-on-3-a.html


I may have missed it in the thread, but, have we confirmed how low the voltage is actually getting in the OPs truck (with a volt-meter) rather than taking the inaccurate gauge at its face value?

 

The plug-in Innova units may not be dead-nuts accurate at the cigar lighter socket but plenty close enough for our purposes here. Just want to see what's going on when the fan motor starts sagging. We're interested mostly in the differences in voltage rather than the absolute value. I can guarantee though, when a motor spools down like that - guess what - the voltage is sagging. Even if the alternator is ruled out (don't discount it) this is a job for "voltage drop" testing. Guaranteed, if done right, it will find the choke point. All that's needed is a voltmeter.

(If you think you maybe know what "voltage drop" testing is but don't know _for sure_, look it up. Either you know it or you don't.) It's going to be a cable, maybe the crimp, or connection at the frame, or firewall, something like that. Or all of them. Each connection is additive in terms of resistance. Even an invisible layer of skunge is enough to prevent good electron transfer. This "fools" the voltage regulator and reduces alternator effectiveness, robs engine starters of necessary current, overheats switches, dims headlights, etc. Grind down to bright shiny metal and tighten securely, coat with vaseline or NO-OX to prevent corrosion.

 

Here's my electrical gremlin in my 89 F250.

The instrument cluster voltage gauge drops to the low side(this also causes the oil pressure gauge to read much higher and temp gauge lower too) when ever I use the blower(high speed), headlights, brake lights turn signals and ect. Even the cig lighter socket is affected as a plug in volt meter will show around 10 to 11 volts. Now at the battery with above gremlin showing, I get a solid 14.4 volts going to the battery. That was with a 2G alternator till I swapped a 130amp 3G one in place as the infamous connector starting to melt on the 2G alternator. Even with 3G alternator problem still present.

I ran a heavy 10 gauge wire directly from the cab(off wiper motor ground point) to ground post of the battery, still no change. So that eliminated a grounding issue.

I finally traced the voltage drop back to the bulkhead connection on the firewall. As I know where the problem is, I just live with it till I upgrade the wiring harness.

One thing I did to properly chase a voltage drop is use a direct ground wire for the meter to the battery ground side. I did that as you could have a bad ground and will be chasing two problems and really confuse yourself.

You think this gremlin problem is hard, try finding a ground fault in a fire alarm panel system!!!

 

This bulkhead connection, is it one wire that runs into this connection that could cause this problem, if so, what colour wire is it and would it be possible instead of putting a whole new harness in to just by pass that particular wire where does this wire run to? is it running into the alternator connector?

 

For this one, shouldn't this be solved by the negative ground to the fender somewhere near the battery and starter solenoid ? Fender should be bolted to Cab and transfer energy that way, would you agree ?

 

Eddie, I would also like to know which particular connection this bulkhead connection is. Thanks!

 

Its the big round connector(87 to 91 trucks, 92 up are rectangle) On the firewall below the brake booster. There are multiple power feeds going through that connector depending on year of truck.

I never found a schematic diagram of that bulkhead connector for my 89 truck which make it harder to figure out. I did find one for a 94 truck rectangle bulkhead connector once.

 

When I run a ground wire, I put it directly on the battery neg post then ground the cab directly. The fenders bolt onto the cab and can cause bad grounding points as corrosion occurs between the metal parts.

That way makes sure for a good grounding.