Sorry for the late replies, I've been out and about.

The needle has done this before, swept over to high but no high speed
fan on, then later fall back to normal with nothing changing.

Now red light blinks all the time but the needle is behaving, for the
time being at least.

Mike

On Jan 8, 2012, at 9:32 AM, David Beierl wrote:

> At 12:02 AM 1/8/2012, Mike Miller wrote:
>> But...my temp gauge goes sl[e]wing up to the red zone and the light
>> blinks.
>
> Less common reason: short to ground in the temp sender wiring.
>
> More common reason:  you have an old-style coolant-level controller
> as found in roughly pre-'85 vans, and it has triggered.  Could be a
> bad controller (and anyway you'd rather have the newer, cube-shaped
> one which will cause the light to blink without visibly affecting the
> needle), but more likely it's an open in the wiring of the level
> sender (the plug comes to mind) or the sender itself which is just
> two s/s pins sticking down into the pressure bottle.  Scrub the pins
> with ScotchBrite, check/clean the connector, make sure the ground is
> good.  If you're running a very weak coolant mix that could
> conceivably cause this as well.
>
> Sight unseen my bet is on the connector at the pressure bottle.
>
> Yrs,
> d