P38 electrical / heating problem

I have a 1996 P38 4.6HSE with 110000 on the clock and have a problem with it.
When the car is at running temperature the temp guage is normally on the half way point. If i turn the headlights on, the guage goes up a bit. I turn the heater fan up a bit, the guage goes up a bit more. If i put my fut on the brake, it goes up again.
It is not a slow gradual increase, it goes up straight away.
Once I take my foot off the brake, the guage drops back one notch straight away, not slowly.

If i have the full beam on, the front fogs, the heater and the stereo on, i can actually get the red overheating light to come on.
The car apparently had a new alternator about a year ago, just before i bought it.

Anyone got any ideas???

When things interact like that it is usually a bad earth somewhere in the system. Check that all the ground pins to the BECM are clean and in good contact. Other than that it's hide and seek i am afraid.

Sounds easy enough but what and where is the BECM?

caddyshack said:

Sounds easy enough but what and where is the BECM?

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BECM, Body electrical control module. Under the drivers seat.

caddyshack said:

Sounds easy enough

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oooh.... NEVER say those words around a P38, she'll take it as a call to arms!