Different models used different fan temp switches in the radiator and so
behave differently. Later ones come on more often and stay on longer,
like 86+, though someone can put any of them in any year. Under the
right conditions I have had high speed come on for long periods in both
my 82 and my 86/87s. Towing a boat trailer in Baja 100+ degree heat at
slow speeds on dirt roads it can run most of the time in my Syncro. Even
then the needle is just barely above the LED but still touching it.

The 83+ radiators have a manufacturing date cast into the plastic end
cap on the passenger side, up high. With the upper grill removed you can
see a small circle with a 2 digit year molded into the center. The
circle is usually the month/week data but hard to decode. The year is
easy to make out though it can be upside down or whatever.

A lot of replacement radiators also have a sticker on the top or bottom
edge that has year/week data on it.

Mark

David Bohannan wrote:

> To those that would like to share their opinion....
>..............
>
> High speed fan hasn't come on in a long while I think due to lack of
> sitting
> in traffic...I haven't seen the needle get that high recently. What on
> earth
> is that high speed fan for? AC on, idling in traffic? Does this all sound
> normal? Or should it not get into those higher ranges with the AC on -
> meaning that the low speed fan is running continuous...
>
> ...................
>
> Thanks for any advice. Wish I knew if PO ever changed out the radiator
> (prolly not)....
>
> Dave