on my 2K XJ, when I first turn on the AC on the clutch engages and I get cool air out almost immediately but the Aux Fan doesn't come on. After a while, the air starts to blow warm, but the clutch is still engaged and turning and still no aux fan coming on. This even happens on the interstate when at 2100rpm.

When the engine gets to about 215 but less than 220 the Aux fan comes right on and cools it back down to 195 and shuts off.

What could be causing the loss of cool air? I have drained the system and recharged it with cooling system stop leak, lube and R134 and the line pressure is correct at 45psi when warmed up and running. Evaporator maybe?

Also, I know from looking up AC issues on different threads that the Aux Fan is supposed to come on as soon as the AC is turned on or when the defrost is turned on. What would be the culprit that would keep the fan from coming on correctly. When I rebuilt the engine I replaced the Aux fan with a new one and since it does come on properly when temp triggered I am thinking it must be a switch/resistor or something somewhere.

Any input is appreciated.

 

'00 E fan is on demand only, 45 (low side?) @ what ambient / RPM? You drained the oil from the compressor changed the receiver/dryer & flushed, then added the required amount of oil?

 

Could be a vaccume problem to the blend doors. Dont matter now though, that stop leak will ruin everything.

 

No I had my neighbor who does home AC stuff for a living capture the r134 with his vacuum pump. He then put new r134 in that had lube and seal in it. 85 ambient temp called for 45-55psi according to the card he had.

So the 00 aux fan is on demand, shouldn't it come on when the AC comes on then to cool the freon running through the condenser? I know it does on my 95.

 

I'm no AC expert, but that sounds high to me.

 

"""""when I first turn on the AC on the clutch engages and I get cool air out almost immediately"""""
"""""After a while, the air starts to blow warm, but the clutch is still engaged and turning""""""" """""This even happens on the interstate when at 2100rpm.""""""

Sounds to me like the fan is working properly -
But the evaporator is icing up.

Check the small copper tube on the expansion valve - the bulb end should be stuffed into the evaporator core to sense it's getting too cold - icing.
If it's not in fully, shove it back in.

The aux fan is to keep the engine cool, not for the AC.

 

Icing up or a blockage from the sealer put in. Run the ac full blast, doors open, wait for the problam to start. Feel the lines going in to the evaporator and see if they are still cold, if they are its a blend door issue. If they arent and the clutch is spinning still, it is probably a blockage.

Start feeling lines on opposite sides of diffrent components. If one is screaming hot the blockage is probably in the component by it.

As far as the electric fan, on most cars it does come on with the ac on. It does cool the condensor down. But on that vehical there is a "relay" that actually increases fan speed based on engine tempature only.

 

Ok, I will have a look at those locations today. Thanks to the last 2 posters for informative answers that provide steps to work towards a possible resolution.

Just to be clear though, this was happening before the freon was recaptured and new added in. It didn't start happening afterwards, just continued to do so.

 

quote,

Check the small copper tube on the expansion valve - the bulb end should be stuffed into the evaporator core to sense it's getting too cold - icing.
If it's not in fully, shove it back in.


no sensing bulb or txv on the evap maybe the older ones but not 97+
45psi is 50 degrees for 134a in addition that pressure will drop as motor speed increases. put a good household fan infront of the condensor to simulate driving conditions(more air across the cond.) that rev the motor to like 1500, or 2000 rpm and hold it there for a minute see if the compressor starts cycleing on low pressure. did youre neighbor put 1 and 2/3 cans of refrigerant in 12oz. cans? system holds 20 ozs.

 

I will do that as well, thanks.

He had a 25lb tank that he filled it from, not the small individual cans you get at the store. Also, I spoke to him last night and he said the freon he put back in did not have any leak seal in it, only the "lube".

Thanks for all the great ideas on things to check!

 

you have electrical problem with fan.
45 psi is too high, but you have to deal with fan first.

 

""""""no sensing bulb or txv on the evap maybe the older ones but not 97+""""""""

Maybe not yours, but some still do. Even some 2005+ TJ's do.

The AC systems has had lots of variations - even several compressors were used - Sanden, Mitsubishi etc.

If it has the copper tube, check it.

If not, check the pressures HI and LO running while and it stops blowing cold. DO NOT SHUT IT OFF once it's stopped blowing cold to hook up the gauges.
If it's blocked, HI will go out of sight!

BE SURE TO WEAR SAFETY GOGGLES - A tiny bit of freon in your eye can BLIND YOU!

Make sure the blend doors are not closing and directing heated air to mix with the cold air. The heated air overpowers the cold air.

The blend door(s) are vacuum operated (2003+ are electric) - check for vacuum leaks -
Find where the vacuum hose from the engine goes through the firewall to the cab.
Disconnect the line, blow cigarette smoke through the hose toward the AC unit inside - while blowing smoke in, have someone look under the dash to see where the leak is.

 

dude what the hell??? the first couple of words in his post clearly state its an 2000 xj yet you post possibilities for a tj and 2003 models (Grand cherokee) and as we all know xjs discontinued in 2001 and ,well tjs are another type of vehicle. so my post is valid. no expansion valve or cap tube it has an orifice.

 

Anyway..the fan comes on with the AC, and when the temp gets up near 220* (217-218). IIRC when my AC was low on coolant, the fan nor the clutch came on. If your clutch is engaging, and your fan is not on, (and you are not at speed), I think there is a problem there. I might resolve that, then see if there is still a problem. Related?

 

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