A/C Woes

As I placed order for the Teflon gaskets, I saw a listing for the complete Rotalock assembly (Compressor fitting, hose fitting and Shraeder valve). With this assembly they included the Teflon gasket and a green o-ring like the one I plan to use on the hose fitting. I feel better about using that o-ring and I'll have the Teflon gaskets for the compressor fitting in a few days.

 

Making progress (my old body only allows an hour or so per day in the garage). Going back to the early parts of this thread, I was convince that nasty desiccant muck had blocked the two evaporator valves which would explain my symptoms. I have now removed both valves. They are clean. I blew thru them at room temp, at 50 F in the garage and submersed the small tight coil in ice water. In all cases the valves were open and easily blew through. I thought the ice water would have closed the valves. I put the valves in my freezer and then the valves shut. Conclusion, no crud in valve, it does stroke open and closed. Calibration may be a bit to the cold side before throttling / closing. I plan to blow through hoses from dryer to each valve connection but I see no reason to go for the solvent cleaning treatment. I have replacement valves and will use them.
Comments please.
Ken

 

Note on o-rings. The green ones were shown to be good for R134a and R12. I am switching to DuraCool (propane) which is kind to most all o-rings.
Ken

 

Raemin
Thanks again for input. My evaporator coil has NOT been freezing; I resolved that a few years ago. My problem was no or little cooling at all. Air temp. at vent only dropped 1-2 C below ambient with compressor pressures in spec.

I still need to check the two solenoid valves. I will test blow thru from evaporator back to compressor suction. Relays and solenoids are still suspect. I sure hope it is not the solenoids! Access to them is terrible even with battery out, and I'm not sure if there is a generic part for them.

Your photos will be helping get the things in correct place around evaporator; so far my parts all look in right place.

One step at a time.
Ken

 

Note the two solenoid valves are on the return vapor line from the evaporators not on the liquid lines. I originally thought they were on liquid to evaporators but not that way on schematic.

 

I tested the two solenoid valves under various conditions from key off to simulating AC compressor and motor running and thermostat switches on and off, all together about 5 tests for each solenoid. In all cases air would blow thru the solenoids indicating they are open all the time. Since they are energize to close, they are not getting power to close. Next I will checking fuses and relays. Previously I could get the solenoids to "stroke" by applying 12 V direct to the solenoids. I have no intention to replace the solenoids.

In the worst case that I cannot resolve getting the solenoids to close via the thermostat signal, I will still be able to run the AC and it should cool, maybe freeze if the new evaporator valves do not restrict the cooling enough.
Ken

 

I will check this by checking relays. If relays do not switch I will go back to the snowflake. This weekend.task.

 

Well, I seem to have found the problem with the Anti-frost solenoids, but not sure what to do about it. Using a voltmeter and motor not running, I followed the manual procedure to test the system. I have Drier Pressure Switch jumped to simulate pressure is okay and I have the oil pressure switch disconnected to simulate motor running. The three relays are all switching correctly: Common relay (X) pulls in with key on. Front Relay (V) and Rear Relay (W) correctly respond with their respective fan switches on and the snowflake switches. Lower setting on snowflake and relay gives power output to solenoid valve to stop Freon flow; raise snowflake setting to call for more cooling and relay shuts power to solenoid. Remember the solenoid valves are Energize to Close. Here's my problem. The output from the relay to solenoid (white and red wire to front and white and blue wire to rear) is only 4.5 V! The common relay has 12 V. So where am I losing the voltage? Do the solenoids pull so much current to draw down the voltage? Am I losing the voltage in the relays and wiring? Note that the Common and Rear Relays are new purple ones. I see no need to change the front one as results match the rear system.

Note that I previously tested the solenoids with the battery removed. Using same test procedure the front solenoid made a very wimpy click sometimes and the rear not at all. I fed 12 V direct to solenoids and they gave a nice sharp click to open and close. So I believe solenoids will be OK if I can feed them 12 V.

Okay, any ideas? Can anyone measure their voltage from relay to solenoids? This can be done at the relay panel; no need to remove battery.

Now that I have established I have an electrical issue (or bad solenoids) I plan to start closing up the Freon system with the new evaporator valves, drier and lots of new o-rings.
Ken

 

I will take relay's out and stroke them at battery and measure resistance on the power contacts (to solenoid). I can switch around relays or even go to some older ones that I have kept. Snowflake seems to stroke the relay coil okay.

I read the link but I only have a fairly good "multi-meter". I think it can measure ohms down to a pretty low level. More tomorrow.

 

I could test a relay setup like the fuel pumps but a solenoid should not require such a drastic measure.

 

After doing a bit of a logic check I changed paths. Since both A/F relays had identical output voltage (4.65V) and one relay is old type and one new type, clearly the relays are NOT the problem and problem was "upstream". The common relay with neither A/F relay activated had only 5.5V, so current to solenoids is not the problem. I delved into the wiring diagram to follow the power supply to these relays. After seeing what all is powered in this one circuit I am surprised there is any voltage left at all! This circuit powers the RH cooling fan (but I have done my fuel pump trick on the three front fans), the two AC fans and the compressor clutch. So I followed the voltage by testing fuses (2) with the AC fan switch on. Voltage losses was minimal 12.3 to 11.9V, and virtually the same with one of the A/F relays activated. Then I measured at the compressor pressure switch and got only 6.8-7V,I checked the feed wire as it connects to fuse board and it was 8.3V. So the clutch load is dropping the voltage 1.5V. The feed to A/F relays is from the clutch wire and since it feeds the common relay at 6.8V there is minimal loss on the return wire to the circuit board. Yes, after all the wiggling of wires and contacts the voltage to the A/F relays is now up about 1V from this morning. Conclusion, clutch is pulling too many amps or wire is undersized in the design. ?? I will recheck all these voltages after plumbing is all assembled. I may freshen up some of the contacts on the circuit board. Clearly there are some voltage losses in the circuit board too, lowering feed to clutch from 12 down to 8.3. I replaced the one fan relay the main power feeds thru but this made no difference.

 

One relay right at the Drier pressure switch would do the trick. Feeding a strong 12V to the clutch would supply 12V back to the fans and relays for the dual air system. I'll wait until I have a system that cools (too much).

 

All components installed and all hoses and fittings snugged up. Vacuum drying and vacuum leak test this weekend.
Ken

 

The first can of Dura Cool has been charged plus a can of Dura Dry to capture any moisture left after vacuuming system. Ran compressor for a few minutes to charge the Dura Dry; the Dura Cool went in without the compressor running. This fluid, propane, is charged with can inverted so liquid is fed but flashes into the system. With local weather only in the 40's no way to determine cooling yet. According to Dura Cool instructions 2 more cans are required but they say this may vary and not to exceed normal pressure limits. Pressure is 2.5 Barg on Lo and Hi side with system static. I will leave for 2 days to see if it is holding pressure. It held vacuum for 2+ days.

 

Second can of Duracool charged. It's holding pressure, so no apparent leaks. It's now too cold to do further testing; hoping for a warmer day.
Ken