Alternator Question

[BurbMan]

Was hauling down I-10 at 65 mph today and looked down and the dash gauge was at 11.5v. Stayed that way for about 15 mins and then went back to 14.5v. I know it was normal when I left this morning and whenever I looked at it today. Got no messages or alerts on the DIC that anything was wrong.

I'm thinking that the alternator cut out and I was running on battery voltage for that period, but the battery was charged enough that it didn't set an emergency message on the DIC. Truck is 162k with the original alternator.

Any insight on this appreciated. Should I continue to run this until I get home next week or look to replace it ASAP?

Also, with the TT connected, do the twin 6v batteries backfeed through the charging circuit to provide additional battery power to the engine if the alternator dies?

[BurbMan]

The local advance had a reman in stock, "Driveworks" brand...case was the identical Delphi that I had in there as OEM. Installed the new unit at the campsite this morning and all is back to normal. Wouldn't be a road trip unless the truck broke down....LOL....

I've found that overall Advance is more like Napa in that they carry better quality stuff than AutoZone, hopefully this unit will be good. Was going to order a GM reman unit from Rock Auto but it would not be here until Thursday and we are running over to Pensacola tomorrow.

[BenK]

Ditto mine since about 2000 (it is a 1996)

But never goes below 12.6 or so

Mostly when things are HOT

It is OEM and rated 120 amps at whatever duty cycle GM has for a 1996 Sub 7.4L

Agree that rebuilt is less than a 50/50 proposition for high demand usage

Look at the stereo kits and some that list that theirs can also 'weld', but they
are not cheap...but that will fix it once and for all. Most are in
the 100% duty cycle range vs guessing OEM at around <40% duty cycle

The auto parts rebuilds usually skimp mainly on the diode assemblies. That is
where most alternator problems comes from. Toss in poor thermal rejection
design. If I could easily plumb in a cold air delivery system, that would go a
long ways in solving my problem

Depends on how long you plan on keeping your Sub and/or the convenience of NOT
getting stuck out 'there'

mysub mysuburban

[Fast_Mopar]

BurbMan wrote:
Am going to order an alternator and belt today just in case I need it. Alternator is on top of the engine and only 2 bolts so super easy to change.

I hate to state the obvious, but I will state the obvious. I have had trouble over the years with the lousy rebuilt alternators from AutoZone and other similar places. I know a local shop that rebuilds alternators and starters, and the end result is always much better than the junk rebuilds in the stores. In my opinion, if you end up installing the new one, keep the old factory one and consider having it rebuilt. The factory alternators are the best cores to rebuild, according to my local shop.

[time2roll]

Put the new alternator on, turn the old in for a core.
Better than doing it on the road as I did last Summer.

[BurbMan]

Belt is still good, no squeal or slipping. Started the burb this morning to go into town and got the red battery in the DIC, voltage at 12v. By the time we got to the office the voltage was up at 14.4 and light went off. Am going to order an alternator and belt today just in case I need it. Alternator is on top of the engine and only 2 bolts so super easy to change.

[boogie_4wheel]

With the burb, turn on all electrical loads (lights, fan at max speed, ect). Then push/pull/wiggle the small plug (2 wire?) on the alternator. Listen for a change in engine speed and load.
We found this to be the culprit on an '01 Dodge last year. The contacts inside the little plug had lost their 'spring' and no longer made good contact on the alternator to trigger it to charge.

[Golden_HVAC]

My guess? There is a 30 amp automatic reset circuit breaker on many RV's to prevent overload of the wire going to the trailer battery. So lets say that the battery voltage was 11.0 on the RV and 14.5 on the truck. It will charge at the max amperage for a while, and might drag down the battery voltage on the dash gauge for a little while, then the 30 amp breaker trips, then voltage goes back up to 14.5 volts.

You might also have some big draw on the batteries that is intermittent too. This can drop your output voltage for the time that it takes to run that item. Such as electric seat heaters, or some other load. Did you run the A/C at that time? Perhaps a failing clutch on the air conditioner caused it to draw down the voltage for a little while.

Next time you see the voltage loss, try shutting off the A/C and see if the voltage goes up suddenly. Either way, it is important to shut off not needed loads while the voltage is less than 11.5 volts anyway.

A friend with a Gm had a problem with his alternator. I had told him that if you put on the emergency brake that the daytime running lights will go off. So when his failed, he drove it home with the emergency brake on 1 click. (I would not recommend that - but he did make it home and not overheating of his brakes either).

It starts making solar look better and better. That will take care of charging your RV battery and lessen the loads on the engine alternator.

Good luck!

Fred.

[thomasmnile]

Not a Chevy, but I experienced a problem similar to your description on my 05 3500 Ram diesel. at beginning of the year. Took it to local Ram dealer, they had it all day could not find or replicate the problem. Strangely, it seemed to occur only when ambient air temps were below 60 degrees, I thought the grid heater might be cycling on/off, but the indicator light wasn't on. Took it to the mechanic that normally services the truck. The culprit, believe it or not was the fan clutch (electric). Don't know what it was or wasn't doing, but the abrupt voltage drop hasn't happened since the fan clutch was replaced. Go figure........

[enblethen]

Yes the TT batteries can back feed to the TV. It is not a good idea. Be a good idea to install a large diode to prevent this.Did you install some type of isolator on the TV to shut off the flow when the engine is not running.
I agree you should check the serpentine belt and the belt tensioner. How old is the belt? It could be stretched to the point that the belt tensioner isn't applying enough pressure.

[agesilaus]

Check your belt tightness if nothing else.