'94 Acclaim -No Headlights in Freezing Weather

The headlights on my '94 Plymouth Acclaim won't work when the outside
temperature is below freezing. But they do work when the temperature rises
above freezing. All the other lights and electrical components work fine
regardless of the temperature. Any suggestions appreciated.

Gary

On Sun, 11 Dec 2005, Gary Kaucher wrote:

> The headlights on my '94 Plymouth Acclaim won't work when the outside
> temperature is below freezing. But they do work when the temperature
> rises above freezing. All the other lights and electrical components
> work fine regardless of the temperature. Any suggestions appreciated.

> It's a US model with no Daytime Running Lights. In the last 2 months the
> car has been giving me a number of electrical problems that usually
> resulted in a fault code 41 ( Alternator field control circuit open or
> shorted). My mechanic noticed that a ground strap had deteriorated and
> fallen off, so he fixed that.

Good...checking and repairing grounds is always wise. Note that these cars
have VERY thin headlamp ground wires, 18 or 20 gauge, which connect to
sheetmetal (body) grounds. It's entirely possible your sporadic headlamp
operability is due to an intermittent ground. Do you own a voltmeter? Know
how to use it?

> He first replaced the alternator & a headlamp relay,

I don't know what he thinks he replaced (or what you think he replaced)
but it was not a headlamp relay, unless relays were added to the headlamp
circuit by you or a previous owner. Acclaims don't have headlamp relays
from the factory. The headlamp circuit is the typical simple type found on
many US cars for many decades: Power via a fuse to the headlamp switch,
from the headlamp switch to the beam-selector switch, from the beam
selector switch directly out to the headlamps. Looks like this,
schematically:

http://dsl.torque.net/images/norelaycircuit.gif

> but it wasn't until he later replaced the PCM with a used PCM that the
> fault code 41 went away and has not returned.

These computers ("PCM" or properly SBEC) seldom fail, but on the occasion
they do fail, the voltage regulation function is usually what fails.

> Is a headlamp switch the same thing as a headlamp relay?

No. Your car *does* have a headlamp switch. It does *not* have a headlamp
relay, unless one was added.

There is, now that I think of it, another failure point equally likely as
the headlamp switch to cause this problem. That is the beam selector
switch, properly "multifunction switch" which controls the headlamp beam,
turn signals, wipers and hazard flashers. When the headlamps will not turn
on, what happens if you pull the turn signal lever towards you? Not far
enough to cause it to click, as though changing beams, but just shy of
that point? Any response from the headlamps?

DS