Arcing coil

[wtd]

Molakule,
You can't hear it arcing over the engine noise, but you can see it when its totally dark. I know GM alternators are not that great. My wife found out the hard way when she got stranded on the side of the road in her 98 Grand Prix. I'm thinking of upgrading to a 140 amp alternator in my truck. I can do the upgrade with all factory parts for about $250 including the alternator.

Jim,
98 was the last full year for this body style but they did make some 99 old body style trucks along with the new style in 99. The coil problem is not fixed and at this point, and I doubt it ever will be. I still need to do some voltage drop testing that Lance suggested. Maybe I'll get lucky and find something wrong.

Wayne

 

[Jim Spahr]

I've got to know. Did the coil arcing get fixed. what was the cause and the cure? I believe that the 98 truck was the last year before the all new Silverado redesign introduced in 99. One would think that all the basic, simple problems like a non arcing coil in the Chevy truck line would have been resolved. Big Chevy fan in SC, Jim

 

[eljefino]

Alternator voltage is supposed to drop off as they get hot-- it's temperature regulation to keep from cooking batteries. When you see a voltage spec for an alt it's at room temperature.

GM's OEM maintenance free batteries need 14.1v or so compared to 13.8 for most others. Aftermarket batteries for GMs might lose a little more water so having removeable caps is nice. GM alt's are calibrated for this 14.1-ish.

You can see as much as 14.6 volts when it's below freezing out; it's to compensate for the chemistry in the battery being less efficient. There's a car battery faq that's pretty good that can be googled.

 

[BOBISTHEOILGUY]

quote:

---

Originally posted by eljefino:
Alternator voltage is supposed to drop off as they get hot-- it's temperature regulation to keep from cooking batteries. When you see a voltage spec for an alt it's at room temperature.

GM's OEM maintenance free batteries need 14.1v or so compared to 13.8 for most others. Aftermarket batteries for GMs might lose a little more water so having removeable caps is nice. GM alt's are calibrated for this 14.1-ish.

You can see as much as 14.6 volts when it's below freezing out; it's to compensate for the chemistry in the battery being less efficient. There's a car battery faq that's pretty good that can be googled.

---

with all due respect, alternators cannot detect heat. They work off of current which produces heat and does affect the conductive ability of a component.

The regulator circuit is designed to regulate which uses diodes. These are a silicon component either with a pn or np junction. Depending on the junction, These diodes are biased which is voltage/current regulated, not heat. Depending on the condition of the diode bridge, it can be adversely affected by temp causing an over-voltage condition which can cause excessive charging and water consumption.

As for higher vcc on the gm's, this can be due to the type of components they use or the load factor in that vehicle. Either way, 13.8- 14.2 is common among most, all depending on conditions it sees when charging.

This is based on all my experiences with gm alternators I've rebuilt. I've not seen any alternator equipped with any type of heat sensor circuit. When a battery is cold, it becomes less efficient and the alternator sees a weaker battery thus producing more output.

Take an extremely cold battery that wont crank in winter conditions, short the two leads, - and + together, allow the battery to heat up for 1/2 min, and this will heat the battery up and actually give it enough boost to turn the engine over. note, make sure water is up on battery before trying this. disclaimer.... use at own risk.

[ October 10, 2003, 04:34 PM: Message edited by: BOBISTHEOILGUY ]

 

[dickwells]

Bob, I would give a little more of a disclaimer with that last tip. Such as "your mileage may vary" and "Could be hazardous to your health" if you don't know *** you are doing. I put it in the same category as spraying ether into a carb while someone turns it over. Yes, it works, but it blows up a few engines and burns a few more.

 

[BOBISTHEOILGUY]

quote:

---

Originally posted by dickwells:
Bob, I would give a little more of a disclaimer with that last tip. Such as "your mileage may vary" and "Could be hazardous to your health" if you don't know *** you are doing. I put it in the same category as spraying ether into a carb while someone turns it over. Yes, it works, but it blows up a few engines and burns a few more.

---

Point well taken.
b.

 

[eljefino]

I googled the "car battery faq". As believable as anything in cyberspace it looks scientifically written.

quote:

---

Depending on the load and ambient temperature, the voltage should increase to between 13.0 and 15.1 volts. Most cars will measure between 13.8 and 14.8 volts on a warm day, depending on the battery type that the charging system was designed for.

Most voltage regulators are temperature compensated to properly charge the battery under different environmental conditions. As the ambient temperature decreases, the charging voltage is increased to overcome the higher battery resistance. Conversely, as the ambient temperature increases, the charging voltage is decreased. Other factors affecting the charging voltage are the battery's condition, State-of-Charge, sulfation, electrical load and electrolyte purity.

---

 

[tom slick]

quote:

---

Most voltage regulators are temperature compensated to properly charge the battery under different environmental conditions. As the ambient temperature decreases, the charging voltage is increased to overcome the higher battery resistance. Conversely, as the ambient temperature increases, the charging voltage is decreased.

---

the only time the regulator would be exposed to ambient air temps is when the car has been sitting long enough that the engine has cooled down. otherwise the alternator is fairly hot when operating no matter what the ambient air temp is.
side note: do batteries actually have "higher resistance" when cold?

 

[eljefino]

Chryslers have a "battery temp sensor" to go with the ECM being the voltage regulator. Since the ultimate goal is apparently overcharging a cold battery to warm it up this seems like a good approach.