Currently having some charging or battery problems as well as a brain fart. Ive either got bad batteries (I hope not, they are new), a failing alternator, or a short somewhere. Is it possible to have a short inside the starter??

How many volts should the alternator putting out right after firing the truck up??

Thanx

 

I've always looked for 14 or so from a good alternator. Just after start, I have seen 13.8 a time or two on mine.


What's the problem??

 

The DR. has problems?

I just ordered a new set of brushes for my alternator from LarryB's. After 180K miles its about time I guess. They are only built to last 100K.

My alternator puts out 13.8v. I think it should be 14.5

Why to do you think its a short? I know it sounds stupid buy check your cig lighter in the ash tray. My son in law had a penny in his and it drained his battery after two days. He replaced the battery & alternator.

Shut everything off and start pulling fuses. You'll see the tinest spark from the circut that is discharging. Trace it down from there.

 

Make sure you don't have a preheater relay stuck "on". Saw a truck do that a couple years back. The alternator was making its 120 amps, but it was mostly going into the preheater grid. I changed that relay, and the preheater and the alternator both actually survived it.

 

What should the battery voltage be?? I havent been able to load test them but I would think they should be reading more than 11.7 V?? When I turn the key, the grid heaters draw them down to around 10.7V...doesnt sound right since the batteries are new ??

Sure would be nice if it would quit raining so I could get a good look at it.

Oh yeah, Dr. Evil has problems....

 

Never checked the voltage at the batteries with the grids lit, but 10v doesn't sound all that bad. They pull ~90-100 amps EACH. I can tell if one or both are lit on mine. Just watch the volt meter. They shut off when the starter is engaged, or they are supposed to be.

I know some trucks have the voltage regulator as part of the PCM.

Is the alternator fuse OK?

 

Just had a problem with mine , but it was overcharging . Turned out to be the voltage reg. which is built into the PCM . Put on an external reg. and that fixed it,( after first spending 2 day screwing with a brand new bad reg.)
Try a search on REGULATOR , some good tricks on how to test the alt by full fielding . When I diconnected the alt I got the same voltage numbers your'e getting . So it's either the alt. not working or the reg/wiring stoping it. Also keep an open mind for the rediculous , good luck

 

Should be at lease 12.7v, 12.3 is on the way out. 11.7 is DIT (dead in truck)

Can you charge them overnight and do they hold a charge?

 

I "think" you may be right....Gonna try to borrow a load tester from work and check them out. They definitely take a charge....I think the alternator may have some issues too...?? It does put out 13.5V...but takes a bit to get there.

The batteries are new (January), but didnt install them until May...I will have to pull the caps and see if there is any acid inside. Just about sprung for Optimas saturday but figured that I would try to sort this out before doing that.

Pulled the fue on the alarm thinking that might be it - but Im pretty much grabbing for straws.

 

Hey Dr. - Isolate your batteries from each other and charge them separately before you load test them. You indicated they had removeable caps, so after you charge them, spend a couple bucks on a hydrometer and do a cell test. If any cell is lower than the rest by 50 points or more, you have a dead cell and the battery is no good. Example: on a fully charged battery, the cells should each read 1.250 to 1.275. A fully dead cell will read 1.100. Or any cell that is below 1.200 is highly suspect. This is the most accurate way to pick up on a battery fault.

 

to check for a drain, pull both negative cables from the batteries. Use a small bulb or a test light and put it between one cable and the terminal. If it lights or glows, you have a drain. Anything less than that, like a brake diode, or stereo memory will not drain enough to hurt it in a couple of weeks of drain.

 

The lead acid batteries put out 2.2 volts per cell so that makes 13.2 volts. so to charge them you should see 13.8 or 14.4 or so volts.

 

You just about on the nail... From what I was taught its suppose to be 13.5 to 14.5 as charging normal range. Anything below 13.5 you no charging. If you over 14.5 the batteries will become hot and start to get gassy.

On deep cycle batteries only you want to be able to over-charge to 15.5 once a month to re-mix the acid / water in the batteries. This actual what I do for the solar system her but its a 24 volt scale. So make that over-charge to 31.0 Volts!

Talk about smellin' hyrogen gas!

 

Well, went out and bought a cheap battery tester (only one in town) - ALL cells were LOW, ranging from 1.10-1.15. This was after the truck sat all day and then ran for 5 minutes.

Do the cheap testers work??

Still not getting 13.5 V out of the alternator.

 

Not sorted out yet - but thanks for your advice. Always appreciated !

The Evil One...