ECM Question
 

Cooling fan comes on at 226* it should turn off at 208*.

Always good to post to the forum before wasting time with the dealer...basically you explained normal operation as Kevova point out. And the dealer is clearly handing you a line of BS...basically they're clueless, but to not look clueless, they instead blame grounding points.

That's maybe HARSH!

There's things that the OP mentions that makes the dealers observation maybe correct. OP mentioned that AC turned on 'only' the secondary fan and if ECM operation was correct AC I'm quite sure should have turned on also the primary.

OP doesn't understand the C4 obviously so I'd think for the OP he first needs to 'learn' the gauge function of the DIC and confirmation of TEMPS from the cluster and NOT the analog gauge. We don't know that he isn't aware and maybe that's what he used but depending upon 'whatever' else the dealer did for the diagnostics is important. OP mentioned none of what the entire diagnostics were. Dealer may very well have done complete diagnostics - I would think 'clueless' doesn't necessarily apply.

Does he have an ECM issue? Maybe - it wouldn't be uncommon for '92/'93. Does he need further diagnostics? For sure.

I don't believe the specs mentioned in #2 are correct as I believe '93 has multiple on/off dependent upon which fan. I didn't look but best I recall that's correct.