Fordnatics List Archive

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Mail From: (email redacted) (Matt Silveira x257)

This is a response (a remissful one at that) to the issue of voltage
drop during hot weather from a fellow member in Nevada.


Yes, I am suffering the same mysterious drop in voltage.

I checked the alternator under load: checks OK

I checked the battery: was a bit bad-- replaced it with new one--
still a slight drop at idle.

I checked the terminals: perfect

I can only suspect the heat negatively affects system charging due to
something.


Anyone know what this could be?

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Mail From: (email redacted) (Frank Marrone)

How much of a voltage drop?

A batteries safe full charge voltage is a function of temperature
and regulated charging systems have temperature compensation
built into them. You might see a "hot" charging voltage
as low as 13.8V while "cold" charging might go as high as 15.2V.

Frank Marrone at (email redacted)

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Mail From: (email redacted) (Clifton Koch)


> This is a response (a remissful one at that) to the issue of voltage
> drop during hot weather from a fellow member in Nevada.
>
> Yes, I am suffering the same mysterious drop in voltage.
>
> I checked the alternator under load: checks OK
>
> I checked the battery: was a bit bad-- replaced it with new one--
> still a slight drop at idle.
>
> I checked the terminals: perfect
>
> I can only suspect the heat negatively affects system charging due to
> something.
>
> Anyone know what this could be?

What voltages are you seeing? The regulation circuits in alternators do not
appear to be terribly well temperature compensated. The colder the alternator,
the higher the regulated output voltage. My Mustang voltage drops from about
14.5 volts to 14 volts as temperature in the engine compartment rises. My truck
(a Ch*vy) goes from about 14.9 volts down to around 14.0. Both of these voltage
changes seem to be directly related with the amount of heat in the engine
compartment at the time, and are not at all related to the amount of load at the
time.

I'll bet heat also reduces the maximum generation capability of an alternator,
but that's just a gut feeling and I have nothing to back it up with.

Cliff

- -----------------------------------------------------------------------------
Cliff Koch
Motorola Cellular Infrastructure Division
(email redacted)

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Mail From: chucko (Chuck Fry)

[Another message that was sent to the -request address. -- Chuck]

Date: Fri, 8 Jul 94 13:12:38 HST
From: (email redacted) (Et3 Donaca)
To: nctams1!freud.arc.nasa.gov!fordnatics-request
Subject: Re: Voltage Drop in Heat

Your problem is one of physics . Current flow decreases as temp increases ,
theres nothing much you can do .

Dangerous D ( advanced electronics tech US NAVY )

INET: (email redacted)