DanG144 said:If you jumped 12 v directly to the clutch connections ( One positive one negative) and it did not engage the clutch, then you have a clutch issue.
Check the resistance of the clutch winding, going from memory (check me in post #1 docs) the resistance is about 4 ohms.
To test the voltage out of the FCM to the clutch, you must put a load on it. A light bulb, a resistor, or the clutch coil. With a load on it, it will go to about zero when it is off and about 9 volts or more when it is on. When the key is on, a cabin fan is selected to on, and the AC button is pushed (and you are not in defrost) you should get 9 volts or more from the FCM.
You are correct. The clutch should not cycle on the A4 cars at all during normal operation.SheeB said:Well yesterday I noticed that the AC was not performing as well as it did, so I checked the fans with the car off and the AC on, and the fans were spinning slowly. Started the car, with the AC on, and the AC clutch engaged and the fan immediately went to high speed. Its about 35c here today. I thought this was odd, so I turned the car off and checked the fans again and lone behold, the driver's side fan would not spin! I assisted it gently and it started to spin slowly as it should so I guess the driver's side fan is the culprit.
I also noticed while driving I could notice the ac compressor cycling on/off, due to the power loss for a split second. I am assuming this is not normal either?
I will certainly take pics, my wife has the car today, so I'll get to it when i have the car backDanG144 said:I would have to trace the ground wire from the fan back. It almost has to be right at the battery, underneath it probably. The ground should also be very close to the FCM. You will have to open up the wiring harness protective cover, tape or heat shrink.
I have no pictures or explicit information on connection 193 or ground 12 - I gave you the words out of the Bentley in the post above. Please take photos for the rest of us if possible.
Ok, sprayed for a good 5 minutes the lower portion of the front of the radiator with the car idling, the fans never went to slow speed or no speed, stayed at high speed.DanG144 said:Spray a waterhose on your condenser coil. This will reduce the temperature, and thus the actual pressure inside the system, to normal.
This should allow your fans to be off rather than in high speed (as they try to run in slow, but I understand your slow speed fans are failed.) As long as you spray the water, the AC compressor should run, if you stop spraying the water within 2 minutes it will probably be at high pressure again. If this is what happens, then repairing or replacing the slow speed fans should solve all of your problems.
If it does not work properly with the water spray you might have a bad high pressure sensor.
If you unplug your high pressure sensor and your fans turn off, you know that is the source of the fast speed fan signal (as opposed as it being from your ECU or radiator thermoswitch.)
I changed my mind about further investigations. This evening I made multiple visual observations of the belt tensioner and pulleys with and without the AC on. The pulsing/surging problem, which is only noticeable from inside the car, is still there and only when the AC is on.TheKid7 said:I plan to not further investigate my "similar problem" at this time. I will just live with it for now. The problem seems to bother me a lot less since I have decided to just live with it for now.
Every time the engine warms up, the problem seems to go away.
Thank you for your input.
SheeB said:Hmm, well I know for sure I have a failing/failed large(driver's) fan which started squealing today randomly. This is what alerted me to something amiss with the ac system.
The fan could have been malfunctioning since last summer, but I did not use the AC much last summer as we got so much rain. I will definitely replace the fan (if not both if I can source out one of the Dorman units locally (in Canada). I will not use the AC till I do this and the high pressure switch. I have not topped up the refrigerant myself, but I have only owned the car for just over 2 years myself.
Is the high pressure switch this? http://www.worldimpex.com/parts/german-ac-pressure-switch_908640.html
Thanks for all the help with the troubleshooting. I will try the AC with a cold motor in the morning and see if the fans still go to high speed.
I wonder if I should check (if it can be done by mel) to verify roughly how much refrigerant is in the system? I think I may have read something in your FAQ about this.
Have you checked your power steering system volume?TheKid7 said:I changed my mind about further investigations. This evening I made multiple visual observations of the belt tensioner and pulleys with and without the AC on. The pulsing/surging problem, which is only noticeable from inside the car, is still there and only when the AC is on.
Is it normal to have a "slight" vibration of the belt tensioner? I will try to quantify the tensioner vibration that I saw as (+/-) 1/16" (not measured). With the AC on, I am not sure if there was more tensioner vibration. If there was more vibration, it was barely noticeable over without the AC on.
Does anyone have any more ideas on what to check to aid in solving my problem?
Note: The surging/pulsing seems to be in about 5 second cycles and can usually be also sensed in the feel of the steering wheel. Once the engine rpm picks up above idle everything seems smooth. The problem is only noticeable at engine idle.
Thanks in Advance.
The power steering fluid level is fine. It seems like the surging/pulsing can be sometimes mildly felt in the steering wheel.DanG144 said:Have you checked your power steering system volume?
How are you coming up with these readings? If you had 17 on the low side the evaporator would be a block of ice. Readings also depend on humidity, ambient temp etc.DanG144 said:At 1500 rpm, blower speed to fast, max cooling. You should have about 200 psi on the high pressure side, and 17 psig on the low pressure side.
It can be dangerous to just add refrigerant to a system, without knowing how much is already in the system. An overcharge can take the compressor discharge side completely full of liquid (no gas space left) and cause pressures to skyrocket, popping safety valves, challenging control systems, and potentially breaking hoses, tubes and compressors.
High Kinetic Energy rotational disassembly of the compressor can be hazardous to your person. That is pentagon speak for blowing it up.
This is why you want to be thorough.SheeB said:Well I tried the AC on the cold motor this morning and the fans did run in slow mode when idling. I let it idle for a couple of minutes and they did not go to high speed? I drove to work with the AC off the whole way and while leaving the car idling, turned AC on and fans immediately went to high speed? Do you think the high pressure switch should be considered for replacement?
hevster,hevster1 said:How are you coming up with these readings? If you had 17 on the low side the evaporator would be a block of ice. Readings also depend on humidity, ambient temp etc.
So when refrigerant pressure was essentially guaranteed to be normal, due to being at ambient temperature, the HP sensor was putting out a pressure in the normal range, as indicated by the fan and clutch response, for at least two minutes at idle.SheeB said:Well I tried the AC on the cold motor this morning and the fans did run in slow mode when idling. I let it idle for a couple of minutes and they did not go to high speed? I drove to work with the AC off the whole way and while leaving the car idling, turned AC on and fans immediately went to high speed? Do you think the high pressure switch should be considered for replacement?