Ok, boys and girls, this is my first post here. If I sound(read) a bit frustrated, it is because I am.

I will try to give you all of the info you need first time through...here goes.

'00 'rango 5.9 2wd

Code P1491...

Replaced relay and fusible link in PDC...2 x's...

Fan does not come on w/ or w/o a/c.

Previous owner had big, bad comp stereo in truck and had installed a ground-jumper to the relay so that fan would stay on when key was on...I have since removed.

I used to believe that I was smarter than most inanimate objects...now, I am not so sure.

Thanks in advance for your sage advice.

Mike

 

I must assume the fan you are referring to is the interior A/C blower? If so, is it the front blower or the blower on the ceiling?

 

P1491-RAD FAN CONTROL RELAY CIRCUIT

When Monitored: With the ignition key on, battery voltage greater than 10.0 volts and

the PCM requests the radiator fan to be turned on.

Set Condition: An open or shorted circuit is detected in the radiator fan relay control

circuit.

Possible causes:

RADIATOR FAN CONTROL RELAY CIRCUIT WIRE HARNESS INTERMITTENT PROBLEM

RADIATOR FAN CONTROL RELAY CIRCUIT WIRE HARNESS OBSERVABLE PROBLEM

RAD FAN RELAY CONTROL CIRCUIT OPEN

RADIATOR FAN RELAY CONTROL CIRCUIT SHORT TO GROUND

FUSED IGNITION SWITCH OUTPUT OPEN

PCM

RADIATOR FAN CONTROL RELAY
ELECTRIC COOLING FAN
The powertrain control module (PCM) will set a diagnostic trouble code (DTC) in memory if it detects a problem in the electric cooling fan relay or circuit Electrical Cooling Fan Refer to On-Board Diagnostics in Group 25, Emission Control Systems for more information on accessing a DTC.
The DTC can also be accessed through the DRB scan tool. Refer to the appropriate Powertrain Diagnostic Procedures manual for diagnostic information and operation of the DRB scan tool
RADIATOR FAN MOTOR INOPERATIVE
Equipment Required:
[ul][*]DRB Scan Tool[*]Volt/Ohm meter[*]Wiring Diagrams section of this manual [/ul]
Test Procedure:
[*]Inspect 10A fuse in junction block and 40A maxi fuse in PDC Power Distribution Center (PDC)[*]Remove Cooling Fan Relay from the PDC and make the following checks at the relay connector:
[ul][*]Apply 12 volts (using a fused 14-gauge wire) to circuit C25 (relay terminal 87) If fan does not come on, check for open in circuit C25 or Z1. If circuits are o.k., replace the cooling fan motor.[*]With the ignition key "off" check for battery voltage at circuit C28 (relay terminal 30) If no battery voltage present check for open/shorted circuit C28 between the PDC and relay.[*]With the ignition key in the "run" position check for battery voltage at circuit F18 (relay terminal 86) If no battery voltage present, check for open/short in circuit F18 between the junction block and the relay.[*]If no problems are detected, install the DRB (refer to the appropriate Powertrain Diagnostic Procedures manual for DRB scan tool operating instructions) and start the engine. Clip a 12V test light to the battery positive terminal and probe circuit C27 (relay terminal 85) When the engine temperature reaches 110° C (230° F), or A/C is requested, the test light should light. If not, check circuit C27 for open.[*]If no problems are detected at this point, replace the cooling fan relay[/ul][/ol]