I know on this vehicle when the ECM's voltage regulator is bypassed, the CEL light comes on. I do not know if it goes into a Limp home' mode too where AF ratio and spark timing revert to preset values with no adjustment for sensor input. I'd probably be able to tell just by how it runs. I know I cannot pass a smog test with the CEL illuminated, and if it is always illuminated then it defeats the purpose of a Check engine light. So I do not want to pursue this option while the ECM'S voltage regulator is still functioning, as neurotic as it is.
If my battery is fully charged, voltage climbs right to 14.9 after starting when cold. Sometimes when hot restarted 13.9 is the upper limit with a wavering from 13.7 to 13.9v. One might expect it to stay at 13.7 or 13.9 from here on out, but for no discernable reason, it will climb back upto 14.9v. I can drive the freeway for 30 minutes at a steady 65mph and see either 14.9 or 13.7, and then there is a very short lived timid 14.1v that peeks its chromedome over the rise on occasion too.
When the battery is discharged, lower rpms cannot get the battery up to 14.9 for a while, but it will also sometimes not even try to exceed 13.7v when depleted, and this is annoying when I am only driving for 5 minutes and want all the alternator contribution possible.
SO, How bout my heat theory. Since the engine's air intake has to be sucking a portion of underhood heat through the ECM, perhaps instead of a battery temp sensor, the hotter air that gets sucked across the ECM, is what is playing pattycake with my drunken indecisive voltage regulator.
As said when driving with the engine cover off, apparently the thermostat opens rather quickly flooding the radiator with hot coolant and I get a blast of heat into the Van, which will then abate nearly completely as I slow down and take my foot off the gas.
Perhaps I can see if I can influence voltage by aiming a hairdryer at the ECM's air intake, or aim a powerful fan at it.
What's you all think about this hypothesis?
HOw about this 50/120 alternator's field current when It gets hot, could the ECM's VR see some of this and use it as a reason to go all batcrap crazy too?
I guess that DMM thermocouple on the Alternator casing could show me any correlation of temperature and voltage allowed.
That is on my neverending list of a Hundred projects anyway. Perhaps a DMM thermocouple on the ECM air intake too.
Grrr now 101 projects!!
Dammitalltoheck!! never get anything done, ha.
