AC temps not as cold and temps fluctuating (1 Viewer)

[TuffMudder]

Last weekend, I made a foolish mistake trying when removing my alternator. I couldn't move what i now know to be the ac compressor far enough out of the way so I disconnected the tube going in to the top of it, result in the ac venting nto the air on my 1990 hdj81.

This weekend I rented a vacuum and gauges from autozone, replaced the broken seal going into the compressor, put on a new dryer and added oil for losses and the new dryer, approx 3-4 ounces, Charged to 30L and 260H (based on a guide and an ambient temp of 90F) and it blew cold...for about a mile. One of the dryers mount screws had popped off under pressure stripping the threads from its hole.

I found another dryer in town and replaced the old new dryer. Recharged to 30-35L and 230 (based off of a second chart that listed different pressures for 90F that actually called for 35-45L, but we had trouble doing that and keep high below 250).

One thing i noticed while recharging is, the low side would hold in the mid 30's and then would suddenly drop to 10psi which would start a slow drop in the high side and a rise in vent temp. It would hold there for second up to a few minutes and then go straight back to mid 30's. System held but vent temps would only get down to 60 degrees at best and would rise back up into the 60's corresponding with the pressure changes.

We evacuated some of the system dropping the pressures a little lower and the ac wouldn't drop below 70F. We charged the system back up, but as before had trouble getting the low side above 30F without the high side the low side. Not knowing what i was doing, i improvised (which is what caused this problem in the first place). I opted to wait for the drops and then charge again. Through shear dumb luck or coincidence, this result in low pressures 40-45 and highs 250-260, and the vent temps dropped to the low 50's but continued to periodically jump up to 60 with the continued pressure fluctuations.

This may be stating the obvious, but each time the low side pressure dropped, flow at the sight glass would stop and then resume when the pressure rose.

I thought about replacing the expansion valve and I have one arriving today, but I have very limited knowledge about auto ac and this is the first time i've every tried to work on one.

Any help or suggestions would be greatly appreciated. Thanks in advance

 

[flintknapper]

Replace your expansion valve, pull a DEEP vacuum on the system.

And this time WEIGH IN the charge. Your system is designed to work with a certain amount of refrigerant. NEVER charge a completely evacuated system by 'pressure/temperature'. Put in the correct amount by weight.

When 'adding' refrigerant to a partially charged system....you are relegated to using pressure readings (high and low side). But when charging a system with zero refrigerant, look up how many ounces the system is supposed to hold and charge that amount in. Simple.

 

[TuffMudder]

Thanks @flintknapper .

This system was originally r12 requiring 26oz's, but was converted r134. I believe in a converted system you add less r134a than the specified r12 weight using the formula (r12weight x 0.9) - 4oz which in this case would be 19.4oz (specified weight is 26oz r12).

Does that sound correct?

If so, picked up an expansion valve today and should have yet another dryer on Thursday. Next weekend i will replace the expansion valve, replace the dryer. Add 3oz of oil for the dryer (?), Seal the system back up, draw a vacuum and hold it for 30 minutes and then replace 1 12 oz can and i guess use a scale to 7.4oz from a second can.

Stop there and hope she blows cold.

 

[flintknapper]

Thanks @flintknapper .

This system was originally r12 requiring 26oz's, but was converted r134. I believe in a converted system you add less r134a than the specified r12 weight using the formula (r12weight x 0.9) - 4oz which in this case would be 19.4oz (specified weight is 26oz r12). Does that sound correct?

With a conversion....typically a reduction of 10%-15% capacity (depending on your components) is appropriate.
IF you have not changed any of the original components (Compressor, Condenser, Evaporator) for newer units designed for R134A, then I am guessing you'll want to weigh in about 23 ozs. See what you get and fine tune it (if necessary) from there.

If so, picked up an expansion valve today and should have yet another dryer on Thursday. Next weekend i will replace the expansion valve, replace the dryer. Add 3oz of oil for the dryer (?), Seal the system back up, draw a vacuum and hold it for 30 minutes and then replace 1 12 oz can and i guess use a scale to 7.4oz from a second can.

3 ounces of oil sounds high. But I don't know what a FSM for your vehicle states. That would be a LOT. I'd be inclined to add more like 0.5 ounce. IF you have too much oil in your system it can significantly reduce the cooling capacity. I am assuming you are running (PAG 46) with the retrofitted system?

Stop there and hope she blows cold.

It is important to realize that a 'retrofitted' system might not be running components ideally suited for R134A refrigerant. As such....you should not expect the same performance as the system was capable of using R12.

But, you should be able to attain 'reasonably' cool air. 45°-50° F. vent temps depending upon ambient temperature and varying humidity. I consider most retrofits successful if you can achieve 30° F. below ambient (vent temps). IF you do better than that....great, but many folks have unrealistic expectations. A good Aux. fan (usually a pusher) can help make a difference too.

^^^^^^ Expand for replies.

 

[TuffMudder]

I am used Pag 46 and had found online that this system call for 3-3.5 ounces for a new dryer. I used that much for the last dryer so now i'm thinking i have too much oil and don't need to add more at this point.

It is important to realize that a 'retrofitted' system might not be running components ideally suited for R134A refrigerant

@Crab Sack care to weigh in on what components you used for the conversion?

So, pending feedback from John or you Flint, I'm looking at no more oil and 23oz's of r134a. It'll be next weekend before i can do anything, so should be enough time to get this reasonably well sorted

Thanks again @flintknapper