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Discussion Starter #1
When I turn on the air conditioner the radiator fans do not always turn on.
Sometimes they do and sometimes they don't. If the radiator fans don't immediately turn on when I turn on the a/c then I will get warm air coming out of the vents.
The engine is not overheating.
After several tries of turning the a/c on and off the fans eventually turn on and the a/c blows cold.

1. I checked the a/c and its fully charged
2. Both fans work when they do come on low speed.
3. A/C does blow cold when the radiator fans are on.
4. Checked the relays in the engine compartment fuse box and they visually look good.

I'm trying to understand why don't the radiator fans come on every time I turn on the a/c. This is an intermittent problem right now.

Is there anything else I need to check?

Thanks
 

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I do know that the fans will not turn on right away. The A/C system high side pressure has to increase up to something like 290 psi before they are commanded to turn on. Maybe your compressor is a little slow to ramp up towards its max output in a timely manner (at times). That would delay the rise of the pressure needed to request the fans to turn on.


An if the A/C high pressure line stayed just below the threshold psi for turning on the fans, I think the A/C would still be supplying you with some cool to fairly cold air, as long as the car was moving along at a nice pace (not so much sitting still).
 

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Discussion Starter #3
That sounds plausible. At the time the air temp was 80 degrees. Started the car and turned on the a/c. The air coming through the vents was warm. Drive at about 30 mph for a few minutes and the air is still warm. Stop the car check if fans are running and the fans are still not running yet.
Get in the car and get on the highway and get to 70 mph. The air coming through the vents is colder but not as cold as it should be. Turn on and off the a/c a few times the a/c is now blowing cold air. the fans are running.

This morning air temp is 72 degrees and start the car turn on the a/c and the air coming through the vents is immediately cold. The fans are running.
 

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Discussion Starter #4
OK this time my a/c is not working . Just blowing warm air.
As before my a/c belt is OK and the fans work at cooling the radiator.

I tried swapping fan relays from the fuse box still no change. The a/c blows warm air at best.

1. Should the fans turn on at low speed if I start the car cold and turn on the a/c?
2. Do the fans have a fan resistor located near the fan motor or is it just the ones in the engine fuse box?

I'm trying to diagnose this I appreciate your help.

Thanks
 

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Are you saying the radiator fans do/do not start turning when the air conditioner is turned on? Have you verified the system has sufficient refrigerant i.e. charged? Approximately when was the last time the air conditioner was used? 1. Yes, radiator fans should engage at some point whenever the air conditioning compressor is running. 2. Don't believe they have resistors.
 

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Discussion Starter #6
The a/c was working a few days ago. The refrigerant should be there however I cannot say that the level is full since I have not check it as of last November. A/C lines are not rubbing no leaks at least at the lines.
I guess all there is left is to check refrigerant level.
 

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Engine fans have 2 speeds an 2 ways to function. The ECM decides when you will get the low or high speed from those fans. One way is with the engine coolant temp. If that coolant temp reaches a temp (like about 230 degrees), the fans will be commanded to turn on at the low speed. If the temp continues to rise, they will be commanded to run at the high speed (to try to bring the temp down). The other fan mode is with A/C operating. Once the A/C is turned on, an senses a high side pressure (say 200 psi), both fans will be commanded to run at low speed. If the high side pressure increases to a somewhat higher psi, the fans will be commanded to run at high speed. If the psi "never" reaches that threshold psi level, the fans will not turn on. If you are low on system refrigerant, the high side psi probably never reaches a psi level to turn the fans on, an as a by product, you won't be feeling much of any really cold air entering the cabin either.

I also agree that you best verify that you have a full/proper refrigerant charge in the system. If OK, maybe the compressors built in clutch solenoid/servo actuator is sticking in the minimum flow position. If it never or intermittently responds to commands to slave to various positions, the compressor would be unable to compress enough of that refrigerant (which has to happen to make cold air).
 

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Your Rifrigerant should be between 38-44 PSI when you check it.
 

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If you decide to have a set of A/C low an high side psi gauges hooked up >>>>> Along with that posted low side pressure range an the A/C running as it should asking for cold air an a lot of cabin fan speed, that high side psi would be approximately 2 1/2 times what the current ambient temp happens to be at the time the testing is being performed. For example >>>>> If its 70 deg F ambient, the high side pressure would be approximately 175 psi. At 90 deg F ambient that psi would be approximately 225
 

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Discussion Starter #10
Thank you for the info. I do plan to rent a set of a/c gauges but first before I do that what is the connector that is on the left side of the radiator when you are facing the front of the engine where the wires got to each fan? Is that another relay or resistor? What does that do?

Thanks
 

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If its that gray horizontially mounted item containing 4 large size wires in an out of it, its exactly that (a connector). Its the master disconnect connector you would seperate if you wanted to remove the fan shroud assembly along with its fans.
 

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Discussion Starter #12
OK hooked up the gauges while Temp was 82 and humidity 41% and this is what I got:

Car turned off cold High = 100 psi. Low = 100 psi.
Car turned on running and a/c on High = 180 psi. and Low = 120 psi.

Radiator fans never turned on while a/c was on high.

Radiator fans turned on once coolant temp rose and then fans turned off after coolant temp decreased.

Tried to swap out fuse box relays still fans never turn on if a/c is turned on start up.
 

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For one thing, the fans will not turn on with the A/C running at Idle until it sees a high side psi of at least 220 psi. The cold engine when off showing 100 psi low an high is close (based on the ambient temp conditions) Looks like ideal would be closer to about 85 psi. I want to lean towards something like a plugged up dehydrator (along side of the condenser), or a faulty thermal expansion valve on the firewall. Could possibly be the beginnings of a failing compressor in the worst case scenario. Showing your results to an experienced A/C tech (who has seen tons of psi problems), probably would be your best bet for an answer/solution.
 
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