my friend has the EXACT same problem on his late 90s blazer. first thought was coolant, so i put more in last week. I think it's pushing about 75 'whatever units they got on the gage' now. still not cold. how much pressure should it have?

 

10 seconds is a long time if counted out correctly....mine cycles about every 10-15 seconds and it's fine at idle/gets ice cold on the highway. Low freon cycling would be every few seconds.

 

Sounds like it is kicking out on high pressure because the condenser fan is not working. It should be around 35psi on the low side. 75 is way too high.

Driving down the road, there is enough airflow thru the grill to the condenser to keep it running.

 

Update:
Today I checked the coolant pressure with a cheapo gauge from Harbor Freight. This morning it was around 35 psi. This afternoon after it had been driven awhile it was 75 psi. I also checked the the voltage to the condenser fan. It was getting 13.something volts but did not run when the connector was plugged back in.
So, it looks like a bad fan motor not cooling the freon and the compressor releasing the clutch due to high pressure at idle. Runs cold at speed due to airflow across the condenser. New fan to be ordered shortly.

Sound right?

Thanks to everyone who responded.
Regards,
mike

 

Yes, it sounds right. The fact that the cooling system functions ok at speed indicates the r-134a refrigerant is fine----leave it alone!!! It is a weighed charge, and if you remove much, even by connecting and disconnecting the low side guage, you can actually loose some efficiency. Get the condenser fan replaced first, so you can correctly diagnose a properly running system. The consenser fan should run at all times that the a/c is energized. ie: if the compressor is running, the condenser fan should also--continously.

 

After ordering a new condenser fan last night, today I looked the fan's fasteners so see what was involved in removing it. Looks pretty simple. Since I had a hammer-like tool in my hand (ratchet) I gave the somewhat rusty fan motor enclosure a couple of good whacks. I turned the truck on and, lo and behold, the fan decided to work. Nice cold AC at idle! I had tapped it before but I guess a tap was not hard enough.
I will still replace it on Friday when the new fan arrives.

When in doubt- hit it.

Regards,
mike

 

Yup...BFH never fails or in your case a BFR

 

Your welcome

 

lxman1- Thanks for the post and also another post of yours that I found that said the fan shroud can be removed by cutting some plastic. Why Dodge made them so you have to disconnect hoses is just stupid.

This fan replacement was a real pain in the ***. I cut the plastic where the upper left coolant hose goes thru the shroud. My replacement shroud also had a slightly different profile on the fan 'spokes'. I tried to remove the battery carrier because these 'spokes' were hitting the fuse box support arm attached to the battery carrier. Then the bolt on the plastic battery hold down wedge stripped. I ended up saw cutting the support arm off and then I was able to wrangle the shroud into place. Fuse box still attached firmly.
Bolted everything back together and everything works.

Thanks again for everyone's help.
mike

 

just had the same problem, it is the condenser fan, make sure it is turning or spray water on condenser then check air at vents. dealer wants 194.98 for assy(won't sell motor by itself) also want you to buy relay and another plug. I found the whole assy online for 104.00 with free shipping at Dodge parts online.com. Hope this helps cause it took me forever to track down problem myself.