Hi
The new experience. Testing the current trought the clutch.
Yesterday I did the next test:
Voltage point test before de black box.
Voltage point test after the black box, just in the input of the clutch coil.
Current trougth the black box and the coil clutch.
Ambient temp 30º C.
I put the engine to work, switch on AC. The clutch engaged, cold air

V1= 11.78 volts
V2= 11.74 volts
A = 3.30 amps.

after 5 minutes, clutch engaged, cold air:
V1= 11.78 volts
V2= 11.72 volts
A= 3.00 amps

after 10 minutes, clutch engaged, cold air:
V1= 11.75 volts
V2= 11.71 volts
A= 2.85 amps

after 15 minutes, clutch engaged, cold air:
V1= 11.76 volts
V2= 11.73 volts
A= 2.70 amps
At this pint if switch off AC, clutch disengaged, and switch on AC again, same current trougth the clutch but NOT ENGAGED: HOT AIR.

My (today) interpretation:
The voltage are lower that past yesterday test because the amp meter drop some voltage (milivolts), not relevant.
The voltage are the quite similar before and after the black box. No news.

The current trougth the coils clutch are dramatically reduced over the time, from 3.3 amps T=0 to 2.7 amps T=15 minutes.
3.3 amps produced enougth atraction force to engage the clouth.
2.7 amps not produced enougth force to engage the clutch but enougth to keep it engaged.

in this type of coil reduced from 3.3 to 2.7 amp means increased the ohms resistance of the coil from 3.6 to 4.33 ohms. If we asume that the coil's material is cupper that is caused by a increment of the temp coils in 69ºC (124 ºF).

Is a terrible increased off temp, probably caused by a shortcircuit af some parts of the coil (spire) a caused to by a degradations of insulate varnish of the cupper wire.

Cuold anybody do similar mesures to compare.

I keep waiting for you

Regards.