agree with above, i used to run with the cooler in line in the summer, and bypassed in the "winter" , or what we call winter here in upstate SC. I had some extra AN lines made up to do this. Swapped out the lines in a few minutes.
But with my temp sensor in the sump, i find that unless i am pushing it hard, or idling in hot traffic, i can't get m
oil temps up very high. I have checked my
oil temp sending unit, it seems accurate. My Stroked Windsor is just loafing along at cruise, and with my 9 qt system, it takes a while to warm up anyway. So unless i am putting a lot of combusion heat into the motor, my
oil temps really never come up high enough anyway.
Like the writer above suggested, my guess also is that you can't get your oil temps up high enough to use the thermostat's function. My oil temps are very rarely as high as 200 degrees, unless i am on the track.
Now i just leave my oil cooler out of the circuit all the time. So probably it is working fine.