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Importance of WOT A/C cutout


85_Ranger4x4

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Does this exist to prevent damage or to free up extra hp when WOT is needed?

AKA I have no ECU or TPS so if it isn't for the safety of the A/C system I was just going to bypass it. I would think the high pressure switch would safeguard the system... I think I can either hit the button on the dash or muscle through it if I need more power.
 
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Yes, it is just to give full power to the driver, i.e. passing.
No, the higher RPMs won't hurt compressor.

But..........it is also to prevent overheating, WOT is normally used when engine is under load, like climbing a grade or pulling a load, the extra load of AC during this time will cause extra heat.
If you are running a carb then you won't have the extra cooling from engine running richer, ECUs add extra fuel with EFI at WOT, ignore O2s, this aids in cooling cylinders, carbs don't have that option.
But as long as you know it can happen you can turn AC off manually.
 
85_Ranger4x4

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I have been thinking... I don't think I have ever made the A/C kick off of anything before.

I tow far more with my F-150 than I ever will with my Ranger... never kicked off the A/C with WOT. I have never gone to WOT...

New brain fart I just had, I could wire up so if the engine starts to overheat I could have it kick off the A/C using a relay in lieu of the "WOT relay"... :icon_idea:

Thinking about if I leave it idle and it starts to get warm or something...
 
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85_Ranger4x4

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Anyone have the wiring diagram of the A/C harness for a first gen?

I find the wire from the ECU to the WOT relay but nothing that details what the other wires are or even which one is the one that goes to the ECU. I suspect the green one goes to the switch on the dash but beyond that I don't have anything to go by.

I know where the compressor and low pressure switch plug in though. Mainly with the two connectors at the left (with the cut pigtails)





 
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FWIW, mine cuts back in after about 5 seconds or so, even if I am still at WOT (that eliminates the overheating theory). So I'm not really sure what it's purpose is (I seem to recall my manual did say something about it being to free up power, but then why would it kick back in?). Both my BII and Ranger do it the same, so I don't think there is something "wrong" with it. :dunno:


I am looking at the diagrams for mine, and I see what is indicated as a purple wire (circuit #462) that goes from one side of the WOT relay coil to the ECU (pin #54) for controlling the relay. The other side of the relay coil goes to the switched power feed from the EEC power relay (red, #361).

The contact side of the WOT relay cuts into the power feed to the A/C clutch coil: Power comes from the dash on/off switch (lgt green/purple wire #348) to the LP cycling switch, after the cycling switch the wire is tan/yellow (#198) and goes to the contact of the WOT relay, then from the other WOT relay contact the wire is black/yellow (#347) and goes to the clutch coil (other side of clutch coil goes to ground, black #57).
The tan/yellow circuit (#198) also is connected to ECU (pin #10) to indicate to it the A/C has been switched on.

This is for both my '90 & '94, so I can't say whether that matches up with what you're working on... (looks like ECU pins #10 & 54 have different color wires on the diagram you posted than what I mentioned)

Hope that helps a little...
 
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85_Ranger4x4

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It is out of a 86-88 BII.

Thanks, I never thought about the computer getting a signal the thing is on, that might come in handy for a idle solenoid to kick the idle up when the A/C is on.
 

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Excellent post. Thank you very much!!
 
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