Takes about 15 seconds to begin running fan after first start of the day. Runs constant. Not fuses, not relays, no codes.

Thoughts?

I assume you mean the electric fan just behind the grill. It has 2 speeds, high/low, triggered by 2 different relays (R 34 and R40). I know you said "not relay" but have you swapped in different relays? It is possible for a relay to stick "on". Otherwise look to the sensors that tell the system to turn on. Cannot help much with which ones though.

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Is the fan still always on with the HVAC selector in the 'off' position?

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The fan is always on with ignition in acc or run position.


Let me very clearly state. It is not any relay, there are no bare or jumpered wires going from Pdc to fan, no blown fuses.

It does not come on or shut off with any selection on the heater controls, nor does unplugging the heater controls have any effect. Unplugging the ambient temp sensor throws a code of circuit high, ambient temp sensor. It is working, and when plugged back in, I can clear the code and not have it return. It only comes on when you unplug the sensor, not by default.


Motor is new. Engine harness has been completely removed with old motor and reinstalled with new. Sensors were all transferred over. Apparently they like to rub through wiring by the filter head, but I see no evidence of this. I also do not understand why that is relative as I have failed to locate any supposed coolant sensor on the driver rear of head or block. There are fuel rail sensors, and map sensor, that is it. Only coolant sensor I know of is up by the tstat and water pump.

Sounds like you have a short somewhere.
Specifically a short-to-hot.

If you pull the relays out, does the fan still come on?
If so, then the short is somewhere between the relay box and fan.

If you pull the relays out, does the fan stop working?
If so, then something is keeping those relays alive that shouldn't be.
Could be a short in the harness between the relay box and ECM/PCM.
Could be a problem with the ECM/PCM.

Could also be that the NO-NC connections to the relays got flipped.
If you are absolutley certain that the relays are good AND you swapped wiring harnesses, then
maybe the connections to the fan relay got mixed up.
Or maybe its the connections to the fan itself that got mixed up.

EDIT:
Its also helpful to know the things that cause the fan to turn on.
1. Engine temp of 205 deg F or greater
If one of the temp sensors is bad it could cause the fan to come on.
2. HVAC system
Its not just the A/C switch and controls that cause the fan to turn on but also the pressure
sensors in the A/C lines play a role.
If the A/C high pressure switch is stuck ON, then that could cause the fan to stay on.

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The fan comes on delayed. Something is definitely telling it to stay on.


Relays are still not the problem. And nothing is wrong between them and fan.

I Didn't swap harness, simply removed it along with the engine so I could clean and put the new engine in.

It isn't a short in any obvious place.



Where are the darn sensors for temperature? The one in tstat/h20 pump area is functioning. It has been over a month since the motor was installed and I cannot remember where those sensors are...and of course the FSM is worthless.

The A/C high pressure switch is next to the battery, right below the alternator.
Try disconnecting that to see if that kills the fan.

If not, the low side pressure switch is on the accumulator, next the the firewall, below
the coolant tank. Pull it too and see what happens.

If its not the AC pressure switches, not the relays, not the temp sensor, and not the wiring, then
its the ECM/PCM.

Unless anyone else has any ideas?

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U.S. Army Retired

There is no freeon in it at the moment. Should have mentioned that.

But, first drive out, the fan did not come on.

Getting aligned and a/c charged as we speak. It wasnt the high or low pressure switch via unplug method. Unplugged all cooling sensors at once, still comes on.

High pressure ac switch was reading out of spec. Problem fixed