I have noticed the hotter the air temperature gets, the Volts drop according to my ArrowForce Scan gauges.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>

Exp: Air temperature 50 degrees – Driving speed of 70 MPH – volt gauge reads 14.2 volts.<o></o>
Air temperature 92 degrees – Driving speed of 70 MPH – volt gauge reads 13.7 volts.<o></o>
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My questions are – Why is there a drop in volts with the rise in air temp ?<o></o>
Is 13.7 volts normal with the temp being 90 degrees?<o></o>
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All winter and spring with cooler temps, 14.3 volts have been the norm for my truck.<o></o>
Batteries and alternator are about 6 months old.<o></o>
This may be perfectly normal, but driving with the gauge displaying Volts, I have notice some change in the reading and would like to know why. Thank for any help.<o></o>

 

Are you running any additional accessories (such as A/C) during the hot weather?

 

Yes....A/C.....But I have tried turning it off for awhile with out any change in the Volts.

 

Sounds to me like the alternator charges based on temperature compensation. Common in RVs to increase battery longevity. I didn't know Ford did it in their trucks, but since there are many functions that change based on temperature, there is no reason not too.

Here is a link http://www.tekrispower.com/pdfs/xant...20Charging.pdf

Steve

 

I'll have to pay more attention, but I'm pretty sure mine has been reading over 14 volts above 90 deg. outside temps.

 

I'll watch mine also. I never heard of temperature compensation in alternator applications, but it would be kind of cool if it did.

Steve

 

Great read Steve, Thanks.

This morning it was 70 degs with A/C, drove to work and the Volts where 14.2 ?

 

109 here last week and my volts were 14.3 at 65 mph....

 

Shoot, I was getting into the notion there was temperature compensation at work. Toss that idea out!

Steve

 

I have the arrow force gauge and my truck does the same thing,when hot out 13.7 with or without ac when cool out 14.3.When It's hot out and I start the truck for the first time that day I get 14.3 but when the truck get's up to temp it will go down two 13.7.

 

Yep, thats exactly the same thing my truck is doing.

What year is your truck ?



I stopped by my local BATTERY WHOLESALE after work today and the alternator and batterys tested fine.

 

So the alternator is topping off the batteries and then drops back to under 14 volts to avoid cooking the battery.

That is a pretty standard program with most charging systems. You have to get over 14 volts to top them off, but sustaining it will damage the batteries. If the batteries are weak or low on water, it will continue to try topping them off.

Steve

 

Thanks for your replys and help Steve, Much appreciated.

But I need to ask, would'nt I be cooking my batteries too in the cooler temps and the Volts at a steady 14.3 ?

 

My truck is a 2000 alternator and batteries less than a year old,even with the old batteries and alternator it was the same.

 

Have you notice in the winter months the Volts being a steady 14.3 volts ?