OBD1 is the computer system used on pre 96 vehicles. I have never really had good luck with obd1 providing much in the way of useful info.
if your vehicle achieves and maintains a normal temp on the gauge, your 'stat is probably ok.
how does it drive?
If it seems to lag at some times and surge at others, but starts and runs ok overall, I usually check the tps first.
My 95 xj (similar electronics) recently started acting funny as described above. check engine light came on. when I pulled the code, to confirm my tps suspicion, the code was for a fault in the ac system. I ignored the code, replaced the tps, and the light stopped coming on and it ran normally again.
good luck!!