Batt volts vs Flashscan log..

[Mr. P.]

...I haven't data logged my 08 5.3 Silverado, but I see the volt meter ranging from over 14, to near 12... Do you know if there's a control mechanism in the PCM to regulate alt output?? As near as I can tell, it's internal in the alt...

Well it all depends, and I'm not sure. I need to go to my alternator folks (Alterstart) and get a brain-dump on these contemporary units. Also, the charging system changed in the trucks in late-2003, so I dunno if the field is self-regulated (like older alternators) or PCM-regulated and how this may have changed in 2003+.

...We were thinking the ecm/pcm is reporting a regulated voltage being used in the pcm.. Y/N??

THAT would make perfect sense - the PCM has voltage divider circuits in it to deliver precisely 5.0-volts to the various engine control sensors, I bet it also has a similar regulated circuit that caps internal PCM buss voltage at 13.0-volts (give or take), that would make a lot of sense because all motherboards use regulated voltage; I would now bet $1 that this is the value being reported by the GM.VOLTS or SAE.VOLTS PID.

...What fans do you use? [We wondered about the 11A, too.]

Funny that you should ask - I make & sell an electric fan kit for GMT-800 trucks (99-07), I've done over 50 of them word-of-mouth during the last 3-years, I retail them for $549 complete/shipped/insured/tested/warrantied. I use SPAL 16" fans, my own proprietary control harness, and my own proprietary low-profile shroud. All wiring is correctly sized (10-gauge) and crimped *and* soldered, with appropriate fusing and relays. We parked a few trucks side-by-side, and my kit pulls half-again more air than the GM 2005+ fans, and those pull half-again more air than the LS1 fans and FAL fans (FAL truck kit is a sad joke). The big SPALs pull 25+ amps at full blow, and when you have a rowdy cam with lumpy idle and the alternator voltage falls for a split second the amperage draw can reach 80-amps (the Torrent E-Fan kit has been made for that).

IMO with what you have shared, the only reason you are cooling as well as you are is because you have a really good radiator; I would also advise you change out to a 160* thermostat (remember, they begin to open at 160*, not fully open at 160*!) and my own truck as well as all my customers maintain a 192-195 running temp at freeway cruise in the 105* summertime heat. 11" fans are just not enough coverage area to keep the truck cool IMO. OR are you running three of them?!

Some pics of the Torrent E-Fans on a project 2-years back (last year's pt.net calendar cover truck, I am proud to say):





Mr. P.

[Chuck L.]

I will go to the 160 stat, as I need to cut all the under hood heat I can... Fighting hi IATS, and timing losses..Building a cold air box today! [100*/45% H again.]
[How do you work around having those turbo inlets breathing rad temp air??]

Do you have/sell a GOOD quality 160* stat? Looks like I may be changing fans this winter. [Perhaps a single 16" with your controls would work??]
If you would, please, let me know what you find out with your inquiry at Alterstart.

Again, Thanks for the input!

Back under my rock....