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Robert
Robert, ASE Certified Master
Category: Dodge
Satisfied Customers: 4275
Experience:  Dodge Master Certified, Dodge Sprinter Certified
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2003 dodge ram 3500 5.9 diesel high side ac too high fan not

Customer Question

2003 dodge ram 3500 5.9 diesel high side ac too high fan not engauging checked power and ground at fan plug and at pressure switch all ok changed fan clutch still not engauging
JA: Has the clutch been slipping? Are you having any trouble shifting?
Customer: fan clutch
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: I am a repair shop I have prodemand still cant figure out why fan wont engauge with ac on
JA: Anything else you think the mechanic should know?
Customer: not really
Submitted: 9 months ago.
Category: Dodge
Expert:  Robert replied 9 months ago.

Hello, welcome and thanks for asking your question. My name is*****'m a Certified Auto Technician with 29+ years experience. I will do my best to assist you. please keep in mind that I may need to ask questions of you before I can answer. When you reply please feel free to add as much detailed information as possible pertaining to your concern.

Has it been scanned for codes? We need to see if there are any fan clutch circuit codes. If it hasn't been scanned yet, please scan it and post all codes retrieved here...

I'll do my best to help but we need to start by scanning the vehicle for codes...

Keep me posted...

Thank you,

Robert

Customer: replied 9 months ago.
I did scan it no codes present
Expert:  Robert replied 9 months ago.

Ok, what are the high side and low side pressures with the a/c operating?

Have you checked for debris in the a/c condenser AND between the intercooler and radiator? These are known for collecting a lot of debris in front of the radiator...

Keep me posted...

Thank you,

Robert

Customer: replied 9 months ago.
there is no debris inbetween any of them I just evacuated and recharged the system when compressor comes on both sides raise normally then as high side keeps raising the fan does not engauge and pressure goes up over 400 I shut comp off to not hit blow off pressure when you hose down condenser pressures run perfect I have power and signal voltage at fan plug and sensor ground also I checked for sensor voltage at pressure switch also it is there along with sensor ground
Expert:  Robert replied 9 months ago.

Since there is no codes present, I'm not certain that there is actually a problem with the Fan Clutch or it's operation. If there was a deviation between requested and actual fan speed the ECM would have set a code....

Read the following excerpt from the Service Manual:

5.9L DIESEL

The Engine Control Module (ECM) controls the level of engagement of the electronically controlled viscous fan clutch by monitoring coolant temperature, intake manifold temperature, air conditioning pressure and transmission oil temperature. Based on cooling requirements, the ECM sends a signal to the viscous fan clutch to increase or decrease the fan speed.

Fan speed is monitored by the ECM. Fan speeds above or below a calibrated threshold will set a DTC. Circuit concerns will also set fan clutch DTC's.

Does your scanner display live data? We need to see if the A/C pressure that is read by the sensor is the same as the high side pressure as read by you manifold gauges...

Keep me posted...

Thank you,

Robert

Customer: replied 9 months ago.
is there a way to ground out switch or bypass to text to make sure if I have a bad new fan clutch or not my matco scanner does not read ac pressures and I cannot control the fan speed with my scanner either
Expert:  Robert replied 9 months ago.

If you had a bad fan clutch you would have had codes stored in the ECM, mainly code P0480 and P0483. As I partially stated earlier, if the fan actual speed was not the same as ECM requested speed you WILL have code P0483 stored in the ECM. --->> Click Here to view <<---

Because of this we need to look for other possibilities for your concern starting by verifying that the a/c pressure transducer is sending an accurate pressure reading to the ECM. If this pressure reading is innaccurate (Low) the ECM will never engage the fan clutch because according to the pressure from the sensor, there is no need to ....

Keep me posted...

Thank you,

Robert