If you have no heat inside the car, there are some simple procedures to follow, assuming you do not have any form of air co. First, check the thermostat. Are you sure that the neddle stays at 12 o'clock at _all_ times? If it does not, replace. Replacement is cheap and easy.
Second, bleed the system. Empty out all coolant, lift front of the car or park in slope and then open the reservoir cap, fill about a litre of coolant, then start engine and open the heater valve fully and proceed with filling. When no more bubbles appear and when the level is steady, close cap, lower car and keep the engine running until coolant is hot and check the heat.
Third, flush the heater core. Empty out all coolant, open the top and bottom heater hoses in the engine bay and attach garden hose to the top one and turn on the water at full pressure. Stop when clear water is flushing out of the bottom hose at reasonable speed.
If none of this works, your heater box is broken and you will have to take apart dash to fix the flaps and the wire controls.
George
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'95 940 Polar LPT (B230FK/AW71; 130k)
'87 740 GLE Turbo Diesel Intercooler (D24TIC/ZF22; 210k)