MARKY MARK

About a month ago my alternator died. I had it replaced along with 2 new Interstated batteries.

I noticed when I start the truck in the mornings it goes through it's normal grid heater cycling. I start driving and at about 18 mph the grid heater shuts off and volt go right up to about 14-15. When I come to a stop sign, the volts drop to about 11-12. As I start driving again, the volt move right back up to 14-15. When stopped, if I put the truck in park the volts climb up to 14-15. Turning the headlights and driving lights off helps too but when I put it in park is when I really see the volts come back up.

Is this normal?

Mark

nickg

Hook up a temporary test light to your grids, my guess is they are being cycled, so will tell you its normal. I dont think so. You could also disconnect the small wires from the grids, or unhook the large wires at the drv side battery that power the grids, either way will disable them then go for a ride to see if you have any voltage drops...

Or you alt is ready to kick the bucket.

opps just noticed you installed a new alt.

OK I'm betting on a grid issue (relays or ECM/PCM)

camelracer

Sounds like the new alternator isn't putting out full voltage when idling in gear. When you put it park the idle speed comes up a bit and the alternator output goes up.

MARKY MARK

Thanks for the info. I'm going to keep an eye on this. Will it hurt the batteries to let this keep happening? I'll probably try disabling the grids like nickg said.

Mark

MARKY MARK

Well, this morning on my way to work (5 miles) the volt guage didn't even get past about 11. Normally it would be up over 14 at 18 mph. When I got out of the truck, it smelled like something got hot. I'm assuming it was the grids staying on? Or the alternator heating up? I'm going to try to find time today on my lunch to unhook the grid heater wires to see if that is the problem.

Mark

Busboy

I would inspect the battery cables for corrosion at the clamps. You could be over charging the Passenger side battery. It could be the grid heaters as already stated.

MARKY MARK

I disconnected the grid heater and that did not help. I put my hand on the alternator and it was pretty hot and smelled like it was cooking. That was after driving a few miles. I'm thinking the new (remanufactured) alternator is having problems. I called the place where I had it installed and they told me to bring it in. Now I'm just waiting for them to call me back.

Mark

MARKY MARK

Went to pick up the truck. They said the alternator was toast. It's fixed now. I hope it lasts longer than two months this time.

Mark