2nd Gen Non-Engine/Transmission Voltage Fluctuaes

[RALLER]

97 3500 I first notice head and dash lights flickering, and voltage gauge bouncing. I load tested alternator at 139 amps with a AVR. Volt meter

fluctuates 13 to 13. 6 volts. Problem with PCM? I have heard of wiring in an external voltage regulator, what regulator do I use and how do I wire it in?

Thanks

Bad Bob

 

[tp0d]

Bob:



Welcome to the TDR!



When this voltage fluxuation happens, is it upon first startup in the morning, with a slightly cold atmosphere?



Sounds like your grid heaters are operating, and putting a load on the system. The grid heaters pull quite a bit of amperage, and will make the voltage gauge move between 1/8" and 1/4" while the heaters operate. They are controlled by the PCM via the intake temp sensor, and usually stay on 3-4 seconds at idle speed, at 1000rpm they stay on longer.



good luck



-j

 

[bavrit]

It is probably your relay that turns on your grid heaters. It is located on the fender well on the drivers side. Mine did the same thing, the relay contacts will turn on and off with vibration. To test it, disconnect your grid heaters, and take it for a drive.

 

[RALLER]

Grid Relays were the problem. Thanks to TPOd & BAvrit. I really like my truck and the

TDR web site.