So progress with the 88 2.8 single fan not working issue. Fan not getting power. Ran hot to it and it works. Traced the wires positive (black and red) runs to the fan relay on drivers side middle relay jumped it with ignition on ( not started ) and fan comes on telling me fan is good to relay ( which is new ) and it has power. I also ran a neg to temp sensor to see if fan kicked on and did not so it's good. I did however find a wire at bottom of distributor unplugged ( prob from the trans replacement and detent cable ) so i plugged whatever that is to the plug at bottom of the back of it. Yes i have read tons of threads and tried what seems to be everything.

 

Isn’t there a fuse under the dash?

 

ah yes forgot to say that checked all and good

 

I am not familiar with your exact fan circuit, but shouldn't it be forced to turn on with the A/C also? Does it?
You said, I also ran a neg to temp sensor to see if fan kicked on and did not so it's good.
I believe that if you grounded the correct sensor, the fan should turn ON. You said it did not, so therefore the relay's coil is open, or there is an open in the wiring to it.
Don't these relays have buttons on the top that you can press to test them?

 

no button on the relay to test that i know of, and no it does not turn on with the a/c. it has been a long day and you are right i typed that wrong. So i guess that solves the problem.

 

ok so changed the coolant sensor( pic 1 with first arrow) and still no fan. Has to be in the wiring. Agree? what are the second arrow first pic- next too coolant sensor and second pic - drivers side behind a/c? (Edit: that is the temp sensor to the gauge on cluster pic 2) So fan comes on when hot ran to it, comes on when jumped at relay, and comes on when checking codes, but not with a/c nor when temp goes up. that is where i am at now.

 

The two senders in the first picture are ; the big one = Cold Start Injector thermal switch , this allows the CSI to operate only when cranking over a cold engine , and the little one is for the ECM to know the coolant temp so as to mix the fuel properly for the given engine temperature .

Oh , and , I'm pretty sure picture #2 is your fan switch ...

 

ok because i was conflicted seen post saying it was temp sensor but you are sure on 2.8 it's the fan switch? i can't find the part on autozone online.

 

Yea , oops , come to think of it ;

I did correctly identify the two in your first picture , those are for the CSI and ECM . The second picture , however , I misidentified . The second picture is for the temp gauge (or light) on the dash , and the fan sender is the one screwed into the passenger's side cylinder head .

 

i think that's for v8's with 2 fans i have single fan.

 

If you jump the A&B pins at the diag connector under the dash, does the fan come on then?

 

yes, and i found the culprit. the ecm. changed it out and now comes on at 238 like it should. Thanks for your help anyway guys!

 

Glad you got it fixed.