Check connectivity at the ribbon on the cluster.  Use a DMM to test it from the plug connector to the back of the cluster where it goes to the coolant gauge.
Z
 

    On Tuesday, October 17, 2017, 10:55:15 AM MDT, Dan N <dn92610@GMAIL.COM> wrote:  
 
 thanks Mark,

will do that today weather permitting... will report back for result

dan

On Tue, Oct 17, 2017 at 9:45 AM, vw_van_fan_Mark <madvws@cox.net> wrote:

> In the engine compartment wiring box there are 2 round 7 pin connectors.
> One of those has a connection for the yellow/red wire from the temp sender
> to the dash. Unplug that connection and look closely at the pins for
> corrosion.
>
> To test, ground the pin with the yellow/red wire, on the side that comes
> from the dash, not from the sender. Grounding that pin while the key is on
> should make the red led blink immediately and the temp needle rise quickly.
> Does it?
>
> Mark
>
>
> Dan N wrote:
>
>> hi all,
>>
>> 1991 tintop Syncro coolant temp gauge not moving at all, the red light
>> blinks and goes away as usual...it's like this since I bought it ..
>>
>> - replaced the coolant temp sensor
>> - check and redo the coolant temp sensor wire connector
>> - check wiring at instrument cluster, blue ribbon looks OK...
>>
>> I am thinking of getting this coolant gauge replacement at VC (
>> http://www.van-cafe.com/temperature-gauge)
>>
>> what else I have to do or to test the gauge before ordering one? (to make
>> sure the one I have is bad)
>>
>> thanks in advance
>>
>> dan
>>
>>