My truck has been frying alternators. One this summer and two in less than 30 days. When taking the alternators to be bench tested the store's machine will fail to read the diodes. The alternators seem to go bad after starting the truck on cold days, and when they do go bad after first cold starting the truck the voltage will surge down and up with the headlights dimming/ heater slowing/radio getting fuzzy. All of which makes me think that my heater grid is staying on too long, and this has been suggested to me.
Anyone had this happen? Think replacing the relay will fix it?

 

grid heaters are made to shut off when the manifold reaches around 60 degrees or you reach 15 mph and when not moving they will cycle for 10 to 20 seconds the most is 30 seconds but that all depends on how cold it is(30 sec=0Degrees or below)

you can see how long the heater gets power by checking the voltage on the two grid heater terminals you can probably just use a test light

hope this helps

 

I put my grids on a push-to-hold switch on the bottom of the dash and only use them for cold starts. The cycling reduces white smoke for the first few minutes after startup, but I don't see that much difference and you don't really need it.

 

Thanks guys. After posting I was doing some research and found just what clementsdiesel mentioned. Ram Diesel Manifold Heater Problems
Gonna break out the voltmeter and start probing things. Its supposed to reach almost 30 degrees today!

 

Thats a nice right up