I have a 99 venture. The cooling fans will not come on to cool things if I am not running the AC. Running the AC turns the fans on, both low and high. Without AC, I have seen the gauge go as high as 3/4 to 7/8 on the temp gauge, which according to a gauge which puts the temp between approx 240 and 247. That is as high as I have let it get. I have red at other sites that the cooling fans will come on when it gets to 'red' on the gauge but I feel they should come on sooner and don't want to risk damage.

I have tested the relays with multimeter after energizing them and they appear to engage properly with little resistance on the closed circuit (not sure I have a good meter to test the resistance amount, but they do have a closed circuit). I have noticed the relays can be placed in any orientaion so I am not sure it that is a problem.

The temp was running dead cold at interstate speeds so I replaced the thermostat (not an easy job) and that solved the problem. I have also replaced the temp sensor next to the thermostat.

Does anyone have any idea what to check next?

 

Jumper across the temp sensor with key on if the fan turns on the sensor is bad.

 

I already replaced the temp sensor which did not help.

 

A trick we use on old motorcycles is a toggle switch to manually turn the fans on. Some guys don't want to depend on the thermo-switch or are too cheap to replace a bad one.

Regardless Kevinkpk's idea of jumpering across the fanstat is a good one. Maybe your replacement is bad too.

Other possibilities are your temp sending unit or temp guage are bad.