[ofelas]

Alrighty. I did the following - installed a '93 AC compressor, condenser, HVAC box, controls, ducts, lines etc on my 91.5

New gaskets & o-rings everywhere. All components cleaned/flushed/dried and new low side switch, expansion valve & drier.

5oz oil in the compressor, 2oz in condenser, 1oz in evaporator & 1oz in drier.

Nitrogen in the system at 300psi and it held for almost 2 hours - no drop in pressure at all.

Ran 26psi vacuum on the system and it held for 2 hours.

Sucked in 40oz of R12 with the compressor cycling at 1300rpm + Max AC + blower fan on high.

Compressor OFF: 50psi low side and 220psi high side
Compressor ON: 25psi low side and climbs in a few minutes to 450psi high side.
Faceplate vent temperatures - 46-50 F

Raising the rpm to 1200-1300 turns the compressor OFF and high side drops almost instantly to 200-250psi

Why am I getting such high side readings, and is it normal for the compressor to be ON constantly until it de-clutches at 1200rpm?

 

[mopar_daddy]

Sounds restricted. High side should never be above 220 imo. Check the expansion valve.

 

[Wilsonphil]

just to be clear, your running r12 correct?

 

[ofelas]

Expansion valve (NOS Mopar) checked out as per FSM.
Yes, R12 with compatible oil.

 

[ofelas]

This morning while idling in traffic - there was a loud hog squeal from the engine bay and mist came through the vents and hood gaps. I assume it was the high pressure relief valve on the compressor venting.
AC worked normally when I drove the truck again this afternoon.Compressor cycles on and off normally now and my vent temps are 40F with this afternoon being 85F with 69% humidity. Pressures are good as per the FSM.
Maybe the compressor burped an air pocket on the discharge side?
**** Dodges.

 

[njmoore53]

Mine did that until I replaced the Fan Clutch. It has to have a lot of air blowing through the from=nt to prevent the system from builing up pressure and venting throuigh the expansion valve. As soon as I can, I am going to try and figure out how to put electric fans on mine so I dont have to rely on a mechanical coupling and engine RPM to get my air flow..

 

[ofelas]

Hi - venting from the expansion valve on the firewall or through the high pressure relief valve on the compressor ?

 

[mcritch]

As soon as I can, I am going to try and figure out how to put electric fans on mine so I dont have to rely on a mechanical coupling and engine RPM to get my air flow..

non i/c is pretty easy. there's lots of room.
http://www.dieseltruckresource.com/forums/1st-gen-ram-all-topics-93/auxiliary-cooling-fans-250585/

i/c trucks are a bit harder because there isn't much room between the condenser and the grill. THIN fans will work though with little modification.
http://www.dieseltruckresource.com/forums/1st-gen-ram-all-topics-93/pusher-fans-i-c-truck-293481/

 

[njmoore53]

Hi - venting from the expansion valve on the firewall or through the high pressure relief valve on the compressor ?

mine was venting from the compressor high pressure relief valve.

 

[ofelas]

Spraying water against the condenser instantly makes the compressor cycle and high side pressure drops to a normal 240psi.
Without water, the compressor is always on and pressures climb quite quick to 450-500.
The fins on the condenser and rad are 95% straight.
Idling, paper is held against the rad but not against the condenser.
The fan barely blows a breeze hot or cold hood open.
I've never heard the clutch engage but truck never overheats.
Perhaps the fan clutch  is barely engaging but the overbuilt cummins cooling system keeps temps down anyway ?
Switched off hot, the fan has some resistance - spins a half turn by hand and stops.

 

[fparkin]

I quick question what low side read ? clutch fan  sounds ok

 

[ofelas]

Hi
Full details/pressures in the first post.
Thx!

I quick question what low side read ? clutch fan sounds ok

 

[ToxicDoc]

Now that something seems to have happened, recheck your pressures and report back please. Definitely sounded restricted. Was 40 oz the correct factory charge btw?

 

[ofelas]

800rpm provides no airflow through the condenser. Yes it's been flushed and the fins are clean and straight.
1000rpm provides enough airflow to keep pressures down.
Fabbing a factory-like rubber sheet - rad to support seal brought high side pressures down from 450 to 400.
Not good enough.
Second gen HD factory fan clutch on its way. Hopefully it has an idle lock.

 

[mcritch]

Now that something seems to have happened, recheck your pressures and report back please. Definitely sounded restricted. Was 40 oz the correct factory charge btw?

38oz of r12 is factory max charge for a 1993 model diesel. 40oz should not make this happen. those pressures with r12 means something was restricted somewhere....

 

[ofelas]

The only thing i can think of is fan clutch not pulling enough air through condenser at idle...as the airflow is fine above 1000 rpm.

Or, the half empty R12 tank had air in it...but still wouldn't explain why it works above 1000 rpm.

Weird.

 

[mcritch]

The only thing i can think of is fan clutch not pulling enough air through condenser at idle...as the airflow is fine above 1000 rpm.

Or, the half empty R12 tank had air in it...but still wouldn't explain why it works above 1000 rpm.

Weird.

any chance that r12 had r22 in it?

 

[ofelas]

Not likely, but how would one check ?

 

[mcritch]

Not likely, but how would one check ?

you cant 100% without sending it off to a lab but you can try by temp/pressure

let the truck cool off completely to ambient air temperature.

get a set of manifold gages, and check the resting pressure with engine off. the pressure should be the same on both sides.

this chart shows the pressures of many refrigerants. r12 should be around 100psi at 90F, while r22 is should be around 170psi.

http://www.foxmacon.com/Tecumseh/Temperature%20Pressure%20Chart.PDF

 

[ofelas]

Its definitely R12 after checking static pressures.

Got mine finally fixed.

My damn fish scales were bad; there was a low charge in the system.

Vacuumed the R12 out, refilled 38oz R12 on a digital stand scale.

Vents are blowing 36F air with ambient of 87F and 88% humidity.

Pressures are 36psi low and 195 high.

Compressor cycles 4 times a minute for 10-12 seconds a time.

New clutch went in anyway...holds a dollar bill against the front grill even while the fan is freewheeling at idle. Old clutch didn't do that.