Fan keeps cycling when AC is on

Supposed to do this to control head pressure....a little fast for me but the concept is good. Being that old is it R-12 or 134A ? Suggests a clog in the system causing high head pressure thereby tripping the pressure sensor to call for engine fan. ( air across coil drops pressure )

Hook up a set of gauges.......if 134 then 35 on the low and 180-200 high at 85-90. Or you can judge the temp of the evaporator. Look at the low side and there is a scale for temp matching the freon type ...needs to be above 32F at idle to more like 36F...because it will drop when your rev up.

Prolly does not do this rolling as coil gets enough air forced by motion.

Get it looked at...may only be a bad sensor.......oh and IMO don't let it do this too long, bad for fan hub. Shut the air off or engage fan manually with dash switch until problem solved.

B model huh? Sweet...... O/O gave me a 3408 for first real job, 450HP, 13 over and 3.90's ....... 3 mpg and flew like the wind. I was in tall cotton for sure.

 

Fan cycling is normal with A/C, but that is too fast. A few things can cause that. Could be a bad pressure switch, if the A/C clutch cycles fast, it could be low on charge. I've even had a bad fan solenoid that would only engauge the fan for a minute or so, then open, cool down, then kick it back on after 20-30 seconds.

You really need to get it diagnosed with someone that has the gauges to check the A/C pressures and capable of diagnosing electrical problems. I'm leaning toward a bad pressure switch or wiring.

 

Good advice.

I'll add one thing. Easy to do. Look at the A/C compressor. With it turned on, does the A/C clutch kick in and out every few seconds? (like your fan is doing)
If so, it's probably just low on Freon. That would explain the erratic fan behavior. Compressor kicks in and starts to build pressure. That causes the fan to kick in. Compressor sucks up all the available Freon and the low-pressure switch shuts off the compressor. The pressure equalizes in the A/C system, and that disengages the fan. Then, it starts all over again.

 

Are you guys talking about the motor fan or the Ac fan ? Bc I just had mine in shop too and when. Have the Ac on above medium it stops blowing and then comes right back on then hesitates.
so I turn the bunk Ac on high and turn the front one on medium and I stay kool,but now I'm back in texas and ITS HOT HERE!!
Putting it in shop but a guy told me today it could be a resistor...hmmmm? Whatta ya think Chalupa???

 

check the plug connection coming from the high pressure switch i had the same problem and the connectors inside the plug were loose, when u unplug the high pressure switch the fan comes on, mine was loosing connection in the plug

 

Thank you,I appreciate that,I'm putting it in the shop today for "emmisision issues"and I'll ask them to check that.Theyve already put a new condenser,compressor,dryer,and some other stuff,can't remember off hand,but I suppose it needs more tweaking.

 

Putting it in shop but a guy told me today it could be a resistor...hmmmm? Whatta ya think Chalupa???

Resistance is futile....driver. No Usually a resistor is all or none like the old Dodges.....used on the coil side to keep from burning out the coil. Resistance can change yes but if bad you would loose all but high speed......as there is no resistance to drop the voltage and slow the fan.

If your blower comes and goes it's prolly a loose conn.

JMO

 

10/4.. She's in shop now,I'm sure ill have it back in 2weeks,right? BAHAHAHA
Doesn't it seem like the shop always says"can't get the part til Tuesday"
Why is it always on Tuesday?...lol Thanks Chalupa..FYI...I did forward you info.
Enjoy your weekend