Archived Voltage Problems. Grid Heater?

[DPellegrin]

When I accellerate in my truck I noticed that the voltmeter gauge drops and the lights flicker under load so I checked all my connections my belt and all that and it checks out fine so I hooked a digital voltmeter up to the truck to watch what it did when the lights flickered etc. the normal operating voltage seems to be 13. 7 volts but when I accellerate the voltage gos all the way down to 12. 8 volts it almost seems as though the grid heater is coming on even though though the truck was up at 180 degrees and it was 75 degrees outside im wondering if there is a relay or something that might be coming on when I accellerate or am I looking in the total wrong place the voltage drops for less than a second when it does it thanks for the help nick

 

[Vaughn MacKenzie]

Nick, a quick easy way to rule that out is to disconnect the grid wires right there at the air horn, or disconnect the relays that run them. Be sure to tape over the ends so they don't touch the engine and ground out (and create a mini 4th of July under your hood) and take it for a drive again.



Vaughn

 

[K5IP]

If you find the grid heater is not the problem, it sounds like your alternator is dropping out. The 12. 8VDC is about where the battery will go when a charge is terminated.

You might be looking for other problems before this is over. Due to so many speed sensor problems, take a good look at your tach when the voltage drops and make sure your speed sensor is working.

Rog

 

[B.G. Smith]

Also look at the belt, may be worn out and when you accelerate it can't take the load of the fan/AC/water pump and alternator. With the engine off of course, grab the nut on the fan with a wrench and rock it back and forth and see if it slips on the crank pulley. bg