Volvo: Volvo 240 Thermostat & Loss of Power, fan clutch, 1992 volvo 240

Question
Hello Ray,
I have a 1992 Volvo 240 Sedan with 159,000 miles on it.  I love this car because it has always been so dependable.  In the past year I have experienced a puzzling problem which my mechanic has not been able to solve.  Last summer I was driving in hilly country when the thermostat indicator rose into the red zone. My car lost power and I had to creep up the hills at 10-15 mph with the heater on.  When I stopped at a garage for help the mechanic could find nothing wrong with my car - the temperature seemed to be within the normal range so I continued on.  I took my car to a Volvo mechanic the next week and had the radiator, thermostat, transmission and catlytic convertor checked.  Nothing stood out as a problem.  Debris around the radiator was cleared away, the thermostat was replaced, and a regular servicing was done.  The car drove normally until March when the same symptoms appeared then went away for awhile.  Last week I drove in the same hilly country as before and experienced the same problems(thermostat high & loss of power).  When driving around town the thermostat goes up and down and I feel a slight dragging sensation.  I live in a flat valley and my mechanic can't reproduce the problem I have in hills.  He doesn't know what to do next.  I want to keep my Volvo for at least another year.  Please help!
Thank you,
Vernice

Answer
Vernice,
I have many times replaced the tempature compensating board in the dash board. The problem with those cars was the temp gauge would go up and come and not read correctly, however these cars never had a loss of power.
Now I would be concerned about the radiator and fan clutch have them tested or just replaced and see what happens. Now also you say that the temp goes up, but is the car really running hot? That is what make me think of the comp board.
As for the loss of power has the fuel pressure been tested and filter replcaed? Check the feed pump and change the filter on the end of that pump also. See if there are any codes stored in the control unit that shead some light on the problem. Loss of power is also possible if the feed pump is bad. No code will be stored for that fault.