A/C not working
Lead Driver
Joined: Dec 2006
Posts: 6,496
Likes: 94
From: So. Jersey
You seem stuck on the fan being the problem, so please post fan speed rpm at idle, and at 1200rpm using a scanner or Scan Gauge II. Then we can compare and see if your fan speed is a problem or not. It should be around 500 idle.
Also there is a PID FANSSM you can monitor with a scan tool that will show low or high when you switch the a/c on
Also there is a PID FANSSM you can monitor with a scan tool that will show low or high when you switch the a/c on
Lead Driver
Joined: Feb 2011
Posts: 8,241
Likes: 155
From: L.A. (Lower Alabama)
From the Tech folder:
Coolant Temp
Some say fan kicks on at 210, some say 215, others say 220. Full explanation: Engine temperature is not the only parameter that the PCM monitors to determine cooling fan operation. This is the reason that you will see some variation in engine temperature as it correlates to fan operation. The operation/description of the FSS (Fan Speed Sensor) from the PC/ED manual has a fairly good explanation as to how the system "thinks". This is not your traditional engine hits temp X and the fan clutch locks up. The fan speed sensor is a Hall-Effect sensor integral to the vistronic drive fan (VDF). The powertrain control module (PCM) will monitor sensor inputs and control the VDF speed based upon engine coolant temperature (ECT), transmission fluid temperature (TFT) and intake air temperature (IAT) requirements. When an increase in fan speed for vehicle cooling is requested, the PCM will monitor the FSS signal and output the required pulse width modulated (PWM) signal to a fluid port valve within the VDF. Engine begins to defuel at 221 deg. The thermostat begins to open at about 190*F to 195*F and is not fully open until about 215*F to 219*F..
I believe it can take more than a minute in some cases for the fan to respond to changes in the signal from the PCM due to the way the viscous Drive operates.
Coolant Temp
Some say fan kicks on at 210, some say 215, others say 220. Full explanation: Engine temperature is not the only parameter that the PCM monitors to determine cooling fan operation. This is the reason that you will see some variation in engine temperature as it correlates to fan operation. The operation/description of the FSS (Fan Speed Sensor) from the PC/ED manual has a fairly good explanation as to how the system "thinks". This is not your traditional engine hits temp X and the fan clutch locks up. The fan speed sensor is a Hall-Effect sensor integral to the vistronic drive fan (VDF). The powertrain control module (PCM) will monitor sensor inputs and control the VDF speed based upon engine coolant temperature (ECT), transmission fluid temperature (TFT) and intake air temperature (IAT) requirements. When an increase in fan speed for vehicle cooling is requested, the PCM will monitor the FSS signal and output the required pulse width modulated (PWM) signal to a fluid port valve within the VDF. Engine begins to defuel at 221 deg. The thermostat begins to open at about 190*F to 195*F and is not fully open until about 215*F to 219*F..
I believe it can take more than a minute in some cases for the fan to respond to changes in the signal from the PCM due to the way the viscous Drive operates.
Thread
Thread Starter
Forum
Replies
Last Post
DanMan7
1987 - 1996 F150 & Larger F-Series Trucks
2
Jul 29, 2018 04:17 PM
Diesel_Brad
1987 - 1996 F150 & Larger F-Series Trucks
13
Jun 26, 2012 03:31 PM
