Truck A/C not blowing cold

[jus]

Ok Guys, Need your Help.
I have a 98 dodge dakota with 135k miles. The A/C works like this. The lower the blower motor speed the colder it blows (About 42 degrees on low). When I turn it to high, it blows about 20-25 degrees hotter. I checked the pressures and the high pressure is about 225-250 lbs and the suction is about 62 lbs. It's my understanding that the suction should be about 35 to 40lbs.What's causing a "high" suction pressure? :devil:

 

[Reel Poor]

Re: Truck A/C not blowing cold

What's causing a "high" suction pressure? :devil:

Are these pressure readings at idle. Should be checked around 1500 rpm's.

Try running water from garden hose across the condensor with guages connected and see what happens.

If no one has added refridgerant the problem could be.

Weak compressor, inability to create enough suction.

Insufficient air flow accross the condensor, weak or faulty fan clutch, or condensor restricted due to bugs, trash, or bent cooling fins. If equiped with electric radiator and condensor cooling fan/fans they/it may not be operating.

 

[jus]

Re: Truck A/C not blowing cold

The pressure readings are at idle. I will try to have someone else throttle the truck while I look at the gauges. I have had a small leak at one time and added leak stop and I believe this stopped the leak. I have also added freon to get the unit going again. In the mornings, it blows good and cold. But in the afternoon, it blows very warm, so I have to keep the control on low in order to get 40 or so dergees out of the grills....I have also washed the condensor. No bent fins or anything like that. The compressor doesn't cycle on anf off like low freon would do to it. You mentioned the compressor could be going out..Hummm... The clutch fan seems to be working correctly....If I changed the compressor, what else would I need to change out?

 

[jus]

Re: Truck A/C not blowing cold

Ok..New readings.....Truck running 1500 RPM's....Suction is 25-26 lbs, Head in running 225 lbs...Washed condensor again, head went real low then back up to 200 lbs...Now my question is still low on froen or to much in system?....
OBTW....The condensor is flacking bad ( Paint cominf off the fins) Could the fins be causing the air flow blockage? Need a new condesor???????

 

[jus]

Re: Truck A/C not blowing cold

Ok..New readings.....Truck running 1500 RPM's....Suction is 25-26 lbs, Head in running 225 lbs...Washed condensor again, head went real low then back up to 200 lbs...Now my question is still low on froen or to much in system?....
OBTW....The condensor is flaking bad ( Black Paint coming off the fins) Could the flaking be causing the air flow blockage? Need a new condensor???????

 

[Reel Poor]

Re: Truck A/C not blowing cold

Question first, Is your compressor noisy.

The system definately sounds like it's low on freon.

But........

 

[rickdb1boat]

Re: Truck A/C not blowing cold

"Suction is 25-26 lbs, Head in running 225"


Was that reading with the blower on high? Put a big fan on high in front of the grille and take some more readings.

 

[jus]

Re: Truck A/C not blowing cold

The inside blower was on high when taking readings. I have not tried the blower in front of the condensor, I do have one of those blower fan. If I over charge the system, will the suction be higher than 30-40 lbs? Or is it, the more freon I add, the lower the suction goes?
The compressor doesn't make any noise what so ever. I am thinking about changing the clutch fan out..It's a 98 model..... When I turned off the motor earlier, I did see the fan make about 5 to10 revolutions before coming to a stop. Don't I need the air flow to be coming over the coils on the condensor by the clutch fan also?

 

[Reel Poor]

Re: Truck A/C not blowing cold

If the cooling fan continued to turn that much I would say replace it. When replacing, use the OEM thermal type fan clutch.

Add the refridgerant at idle, periodically stopping chage and bring the engine to about 1500 rpm's, pressure should run about 32 -35 psi low side and not over 250 high side.

The more freon you add the higher the pressures will run. An over charged system will NOT COOL any beter than a low charged system. Add refridgerant slowly and keep checking pressure and vent temperature.

 

[jus]

Re: Truck A/C not blowing cold

Thanks Guys for the help...This place is the greatest.8)

 

[ob]

Re: Truck A/C not blowing cold

Many vehicles,maybe yours,has a tag or label in the engine compartment that contains the factory weighed charge of refigerant.Saves a lot of trial and error charging methods.

 

[jus]

Re: Truck A/C not blowing cold

Replaced clutch fan and cleaned the inside of the condensor yesterday. Man what a difference. I can now feel the air drawn across the tubes. I think the clutch fan was the problem. She now blows 40 to 45 degrees on high......... Thnaks to everyone that responsed!

 

[Reel Poor]

Re: Truck A/C not blowing cold

8) 8)

 

[Reel Poor]

Re: Truck A/C not blowing cold

8) 8) 8)

 

[rickdb1boat]

Re: Truck A/C not blowing cold

8)