Thermo switch resistance value?

[George Tur]

My son is having starting problems with his 87 5ktq. One item that he checked
is the thermo switch on the side of the block. This is the two prong one.
According to the Bentley the switch should have a resistance of 20 ohms when
cold and then show infinite resistance when the car is hot. Tested the switch
and it showed an infinite resistance when cold so he ordered a replacement
switch. The switch came in yesterday and a quick test showed it has an
infinite resistance when cold also. Anyone have experience testing this
switch? Is the Bentley incorrect with the test procedure, or did he get a bad
switch?

George Tur
91 V8