The temp gauge has a circuit board that makes it inaccurate in the middle position, which corresponds to everything from about 170 to about 210 degrees. This is done so the average person does not worry about moving gauge pointers. If you are outside of this, you are too hot. The upper hose is the wrong place for the fan thermo. That is the hot place. You want the fan thermo on the cold side of the radiator, where Volvo put it, either in the radiator or in the lower hose. You also want to use a fan thermo of the proper temperature. The late Volvo push in unit for the radiator is good; the early one (pre 86) is too hot. You want one that turns on around the same temp as your engine thermo or maybe a little hotter so the radiator can do some of the work. I use a 180 degree engine thermo and the stock Volvo late model (86 on) push in radiator fan switch (part number 1274962-8 or 1378504-3) that turns on at around 190 to 199 degrees and off at around 188 to 180 degrees. This switch should also be fine for the 189 degree engine thermo. The 197 degree engine thermo is probably a bit hot and should be replaced with the 189. A switch from the aftermarket or another car in this range that you adapt is fine.

Also you need a fan that is powerful enough to cool the engine. Not sure what you are using. A 12 incher is insufficient. I use a 16 inch fan that draws around 12 amps and pulls around 2400 cfm or more. A 9 or 10 amp fan that pulls 16-1800 cfm is marginal if you have AC.

It is also possible that your engine thermo has failed or that you have another cooling system problem.

Philip Bradley