a/c charged and cooling

[kglowacky]

well today was a big test for me and my truck. After driven it for 2 summers in Houston without a/c. I decided to see if an old factory a/c system with only a new type compressor and a orifice change would cool. Well it did with a couple challenges still left
Info. 78 c-10 Silverado, new r-34 compressor and condenser. 2002 Camero ls 1 and 460 e.
Here are what I am trouble shooting.

idle is good and when I turn on a/c it adjust perfectly
cold air
had to bypass a new binary switch. Going to go back to the low pressure oem typed switch. hopefully it will work.

Then my mechanic put the truck on the computer, and all was good except it threw a alt. volt code. At idle no a/c 13 volts. Turn on a/c drops below 13 not sure but my guess 11.5 sometimes it will come back up at idle sometimes it doesn't this is in drive sitting still. Go down the road it goes back to 13. He thinks my alt needs rebuilt. I thought I read somewhere on here 12,8 is normal.

last my engine temp running 181. He thinks too low. I have it hooked up when turn on a/c cooling fans come and run all the time. I also have a big, oversized radiator. I am old school and always believe the cooler the better. He says maybe running to cool and may affect my gas milage as it is around 10mpg,

last on MPG I have a 3.70 rear end ratio gear thinking of going to a 3.07. Any thoughts how much this will improve my milage?

Thoughts???

[Jason Banks]

I kind of agree with you on temp. My straight 6 truck has a 4 core radiator and can idle in a 4th of July parade for hours. My LS swap, I'm getting up to closer to 212+ when the high speed fans kick on. I'm pretty sure your mechanic is right about it being more efficient/clean burning at higher temperatures.

I think you can mathematically what kind of increase in MPG you would get out of the lower gears, but you are still driving a brick into the wind, I'd imagine the improvement is minimal, since you already have overdrive, the RPM's at speed are not that high anyway...

[Rich84]

10 MPG is quite low. Is there a chance that your odometer might not be accurate? I have a 6.0 with 3.73 gears and average about 15MPG around town on 2 different trucks (1986 long bed, 84 stepside). They both run at 195 degrees. Fans come on at 205 IIRC.

[clay68c10]

Your gearing should be fine with the 4L60e. 3.07 would be a downgrade. Look at some online gear/rpm calculators and compare what the stock LS equipped trucks run for rpms at different speeds. I bet you're close to that now.
Get the right 195 thermostat in there, it's probably not helping you mileage.
Those low temp thermostats don't fix anything, these engines are made to run around 200-210. The stock fan settings are higher than you would think, like low at 210, high at 220.
Your system voltage is low, 13-14v at idle is normal. I'd say your guy is right, it's new alt time.

[jjzepplin]

Off topic... Could you post a pic or two of your AC system?

[kglowacky]

here's a couple pics of my a/c system

If you need anymore let me know what it is you are looking for.

[Hart_Rod]

You should be seeing about 13.7 volts if the alternator is charging correctly.