Thermostat or Thermostat and Water Pump
 

My coolant temp light to the right of the temp gauge is always flashing even with a cold start.
The temp gauge stays on 0 for 10 - 15 minutes and then jumps to the max.
The heater provides absolutely no heat

I would appreciate comments.
Thanks

Have you checked your coolant level?
Sounds like it could be a bad coolant temperature sensor or a connection issue.

From another thread:

as mentioned above there is a sensor on top of the engine passenger side. I replaced mine cost about $35, also there is the passenger side engine vent fan behind the vent, mine was binding I got a used one for about $50. Could just be low coolant level, I have found just a slight decrease sets it off.

+1 on the coolant level. The temp gauge does not work in steam or air, needs to be in water. Coincidentally the heater core will also not put out any heat without water circulating. Be sure to use the proper coolant and purge the system if it is low.

Maybe 'burp' the cooling system ?

The coolant level is good and the reservoir is overflowing, so it is over heating.

I would try to burp the system and while the car is running blast the heat. Could be your thermostat. Mine was not working. I replaced it with a low temp one and new water pump and worked fine after.

http://986forum.com/forums/uploads01/Box+Coolant+Schematic1432596358.jpg

Please have a look at the attached cooling system diagram. The cabin heater always has coolant circulating even with the thermostat closed. If the problem was a bad thermostat you would have extreme heat output. So since you have no heat you either have no coolant circulating or your climate control system could be malfunctioning. The common denominator to your symptoms appears that you have an airlocked system or a water pump with no impeller or accessory belt is missing. You might check the belt is still there and if it is I still recommend you to purge the system. The tank can be full but will boil over when the engine overheats. If you can get an Airlift great otherwise Pedro has a procedure you can use on his DIY site.

Please also note there is no temp control valve to the heater. Heater always has full coolant flow. Increasing cabin heat simply redirects more heated air to the cabin.

Thank you.