Hope my suggestions help!
If all else fails, first unplug the left fan and apply full battery voltage (13.6VDC - or so) between point B and point A. THis tests the fan motor. Motor windings may be OK when running at 6VDC but at 12VDC there may be enough voltage to cause heat/bad connection shorts.

If that test passes, I would attack this problem like this:
Ground your meter to the battery negative - dont trust any grounds
at this stage, put it on the 20VDC scale

TURN ON IGNITION
With FAN2 OFF - you should see 12 VDC at C1 going to your PCM
With FAN2 ON - You should see 0VDC AT C1
I am sure this test will pass, it checks to see if RLY 43 and 44 solenoid is being grounded.

with FAN2 OFF - you should see 6VDC at C10 of Relay 44
With FAN 2 ON - you should see 0VDC at C10 of Relay 44
If you see 12VDC at C10 with FAN 2 on, you have a bad wire, or bad relay socket or bad ground between C10 and G102 ground. I assume the relay itself is OK since you changed it a few times already.

With your meter still grounded to the battery negative terminal, check the voltage at different locations along the path from C10 to Ground, i.e. at A11, F11 and see where it goes to 0VDC. The open wire/relay contact will be between the last place you saw 12VDC and where you measure 0VDC. As others have suggested, I believe the problem is likely here as well.

 

[QUOTE=lionelhutz;1587912509]I "already thought about it and it still makes no sense"

Yes it does. Look at the schematic

"Low fan commands the low output and high fan commands both outputs."
That's true. Please explain to us how the left fan could possibly run on high with the low speed relay not energized. The power comes from fuse 49, threw closed relay contacts. The ground is provided by relay 44 being energized.

"What you are suggesting is that the PCM programming somehow got corrupted just enough to mess with the fan logic, which would be rather unlikely considering there are checks in the software against such things."

What I am suggesting is a couple of easy tests for the op to perform. If the ground to relay 45 coil is missing, he would have 0v to the left fan on high.

 

With all due respect, I would disagree. If the ground was missing on the coil of relay 45, then there would be no power to the fan on low speed. Since the fan is working on low, it must be good. Your problem lies in relay 44. It is either the ground for the coil at A10 is missing through the PCM or the ground for the N/O contact at A11 is missing. I suspect A11 because Relay 43 coil uses the same ground and relay 43 obviously is OK.

 

foggy: are you sure that relay 44 is closing when commanded? Measure voltage across solenoid terminals before and after commanding; should be close to zero volts (actually floating) before commanded and a steady voltage after command.

Just a thought.

 

I am constantly amazed at how many things that pesky ignition switch can screw up on our cars. I am very glad I was proactive with refurbishing mine, especially considering all of the electrical issues I've had in the past.

 

Who posted anything about the relay not being energized besides you? Clearly, relay 45 MUST be energized because the low speed fan mode works which rules out any PCM or wiring failure driving relay 45.

I already posted 3 failure modes related to relay 45 that would explain the OP's symptoms. The same relay 45 that everyone else except you is pointing to as the likely culprit.

 

UPDATE :
Weird.... that's all I can say
With my OTC Genisys Scanner when I command the fan 2 on, only Right Fan comes on high.
As we know...
So , I took out and drove it. Got it hot.. Then parked it and checked out what is
does all on its own.
Results: at 185* the fan 1 (slow speed) both fans come on.
wasnt really hot out so the slow speed kept temp in check.
When I crank up the A/C, the low speed fans stay on for a while, then
after a while, HIGH SPEED KICKS ON and cycles periodically....
SO: when this happens, both, YES BOTH high speed fans are ON..
What the hell???? IF i command FAN 2 to ON with OTC, they both come on
HIGH only when AC is on...
SO I guess I don't really have an issue at all. NO idea why the OTC won't command
FAN 2 operation at both fans.... but in real life, they both kick on when AC on.
I couldn't get it hot enough to see if both Fans Come on HIGH with just Temp Input.
Thanks a ton for all your help.
Maybe it was just running a bit hot with the stretch fit bra on it..
I havent' really ever had it on while doing in town driving with AC on.
I just put it on for highway protection.....
Lots of time wasted, but at least I learned how these fans work now.
Thanks Again

 

I'm glad that you resolved your issue, or lack thereof!
It was fun just to read all the posts and see how other guys attack a problem. It gives everyone a few points of view and new insights on troubleshooting.

 

I just reread post 16. Without having his voltmeter grounded at the battery, it could read 0 volts across the plug for the left fan. He measured across the plug, that won't tell you which is missing. So lack of ground to the fan will show 0 volts.
MY MISTAKE!
That said, he did as I suggested and ran the engine until the fans were commanded high. Both ran. It is possible there is a problem with the way his scanner commands high speed operation.

 

As a general rule, when measuring voltages on anything, whether it be a car or a spaceship, make sure you have a solid reference to ground for your meter. I spent the last 40 years learning this