Check my post for the AC. Yours is also a '89 that got converted. Puts to much pressure on the high pressure hose that is aged.
See if you have the exact same problem. My band-aid worked so far.
Idle coolant temp. - it is wise to power the fan temp from 102c to about 95c. Not much lower as it will run too much.
It is best to just put the resistor in and adjust the value to your liking with the value of that resistance. Mine turned out to be 1.2Kohm.
Yours maybe slightly different.
With all the tolerances needed, you are basically fine tuning the cooling system specific to your car. So it will be custom trimmed for you.
I'll take a look this weekend with adding in the resistor.
Any ideas on low speed aux fan being inop?