The cooling system light and coolant level relay (picture will follow...)
Since my Red van coolant level/high temp light (the one behind the temps
needle in the cluster) did blink for ever this morning, i had to find the
truth about it... No, coolant level was find and temp also. So i had (I
thought so)a coolant relay problem, everytime this happen, i was humid outside.

Anyway, we did sone heavy testing this morning on my van and on an 87 to
find out everything about that scary light.

Here it is:

That light as a few function on all year and not only 86+.

First, this light will blink when you put the key ON, even if the engine is
not working, it as nothing to do with the engine working or not, nothing!

Now, mine was blinking for ever, temp needle was normal.

So here is the short story for now, a web page will follow when i have time:

-The light and the temp needle are in someway related

-The light will blink for 2 reasons, first if you have no coolant in the expension tank and the
second, to show you that the temp needle is to hight, and that, on all years.

-On 85 and below, if you miss coolant in the EXPENSION tank the light will
blink and the temp needle will rise like crazy, even if the engine is still
ok, on 86 +, only the light will blink but the needle will stay normal.

-The relay! on all van we have a coolant level relay, yes, i said level, and
this one as nothing to do with anything else than coolant level! when the
level is low, the relay go on and rise the temp needle and blinking ligh go
ON, if you unplug the collant level sender wire, it will also rise (it take
about 3 second). Like i said, the neelde will only rise on 85- van. I you
remove the relay, or this one is defective, you will never know nothing, the
coolant light will blink at start up (this fonction is into the cluster!)
and the temp will operated normally. To be sure that the relay is good,
unplug the wire on the coolant level sender located on the expension tank.
Of course, the coolant level sender could also be defective!!!

-Now, if you unplug the temp sender on the engine and ground this one to the
engine or any metal part, blinking light gos ON and temp goes up like crazy.
That is 2 different thing but they look the same! If unplug, not grounded, it will simply
not move (85 and less)

-Now, in my case, i did some testing, relay was replace or not even on the
van and i still had the problem??? when the ignition was ON, the light was
blinking slowly and that from 5 to 15 second it staid ON... this has NOTHING
to do with any sender, gauge, relay or wire... only the cluster was the
problem, imbeded in that one is a small circuit, the check circuit... this
one was BAD!!! i had another cluster and the problem went away!!!

So, lets go deaper! if the light blink at start up and that for a long time
and/or forever, the cluster could be the problem because if you had a low
coolant level situation, the needle would rise crazy on 85 and less and on
86 + you could also have a coolant level problem.

If the light blink and the temp needle rise like crazy, you may have a short
on the temp sender or/and the coolant level sender on 85 and less!!!!!
frigging crazy but true! but you may or not know that the relay is working!
on 85 and less, you know!

Shit, lets call that light the craSY light!!!!

I'm lost myself now!

How to be sure of anything now! well, if the light blink at start up you
know the light is good,,, yeaaaaaaaa! if the needle move, yeaaaaaaa again!

If it goes off after 5 second or so, yeaaaa again! But if it goes ON wile on
the road! well, mostly you have a coolant /temp problem, well, it was design
for that matter... but!

So, the relay is ONLY for telling you that the coolant level is low, but! if
it's dead, you will never know, bad! But the rest may still work fine!

To somewhat prevent all that crap... you should replace the #42 or 43 relay,
replace the coolant level sender in the expension tank and why not, the
coolant temp sender. Make sure the wire to this one is ok.

Part 2, well, there is no part 2, at least for now. I have to put that info
on a web page for now and reflect... i know i'm forgeting some stuff, but
i'm not sure what... crazy light!

So, in any case, if the needle for at the fully hot position and the light blink, you must
have a short somewhere.