Voltage Flux with temperature

[Basshopper]

Does anybody else have this problem when it is hot outside my dash voltmeter reads below 14v turn on the air both front and rear fans on high and headlights and it drops way down like it is discharging around 8v. When it is cool out under the same draw it stays 14v or slightly over like its charging. Is it guage or is it alt effeciancy with temperature or behing door # 3 ?????

[DmaxMaverick]

High underhood temps, compounded by high summer heat, can cause all kinds of havoc.

The heat can cause a weak alternator to fail, batteries to discharge or vapor off, electrical connections to become resistive, and/or the I/P gage to display the incorrect voltage. It definately indicates some part of the system is failing, or about to fail.

I suggest you start with reading your voltage with a volt/ohm meter at several points in the system when the voltage drops. Check the batteries, with engine running and off. It could just be the gage. More likely a ground that's going south. If you haven't cleaned the ground wires and batterie connections lately, now would be a good time. You'd be surprised at how many problems just disappear when a battery terminal or bad ground is cleaned up. To test your grounds, use a set of good jumper cables. Use them to connect the frame to the engine and body. If the voltage jumps up, it's an easy solution. If not, then it is more likely a component failing.

Good luck.

[CareyWeber]

Check you battery cables (both ends of each) I had these troubles till I replace all my battery cables. I lost 4 alternators (Napa Lifetime) till I replace the cables since then about 40K miles no more alternator issues.

I used 1 gauge welding cable for my cables. I also used 1 gauge cable from my alternator to the battery.

When split the cable to inspect the old ones they had corrosion running down inside of the cable to the starter and the cable to the alternator. :mad:

Also do Dr Lee battery post fix too.

I wish I could run group 31 comerical batteries in my truck rather than these crappy side bost batteries. ;)

Carey

[jmp1945]

Don't forget the fuel heater is active below 75* and might be causing the alternator to see a different "need" than in warm temps. Mine doesn't go as low as you mention, but is noticeable.

[jspringator]

It's almost certainly a Cable/connection issue. I replaced my Cable with 1/0 cable, and added a separate ground between the batteries. Once corrosion wicks its way into the cable, there is no saving it. On the wiring to the main fuse block, corrosion had spread from the battery all the way to the fuse block. Get a set of Optima Batteries and use the top posts.