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Discussion Starter #41
Another quick spurt of gas came out yesterday. Only got warm enough to test it today. Ambient 28 degrees, vent 11 degrees. About the same as the last update. Not good enough, but I'm not sure if it's going to get much better than this. Will get the gauge back on it and see what the pressure is like before doing any more purging. Maybe play with the valve again, too.

Monday is supposed to be 37 degrees. Sounds like a good day to get this finally nailed down.

Edit - gauge says everything's fine. It's averaging a little lower pressure now but still well in the green zone. Let a little more Duracool out, and got 9 degrees at the vents. I suppose that's a bit better. I'm thinking I'll be setting the valve back to 1/2 turn CCW and see what that does for it.

Starting to really hate variable displacement compressors.

Edit 2 - I think I've decided to finally get smart about this. The article says to adjust the valve with the system running, so I'm going to drill that hole so I can do it. I found one owner's report that suggests I've already gotten the best out of the system with this refrigerant (I'm getting better temps), and I am now getting the bubbles in the sight glass, so the charge level is probably bang on. Moreover, the valve would be easier to tweak with 134a because the pressure transducer for the rad fans is expecting R12 pressures. It may not be kicking the fans on often enough for the Duracool. So, I'm going to simulate highway driving by forcing the rad fans on while I lie under the car and adjust the valve while watching vent temps.

This stuff may never cool as well as the original R12, but maybe with a little more tweaking I can get by long enough to visit the US and find someone to help me convert it to 134a.
 

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Discussion Starter #42
Change of plans for today... I will still try to drill the adjustment access hole, but all I will likely end up doing today is a minor tweak to the main control valve, setting it to about 1/3 turn CCW. No more refrigerant will be purged.

I believe I found the key to unlock HC-12a's performance in this car. I suspected the fans don't run often enough in the default configuration. The fan cut off switch is looking for R-12 pressures, and not seeing them as often. Therefore the fans run less often. Therefore, the system doesn't perform properly. So, what I did on the weekend was I went out there and jumpered across the fan cutoff switch connector, thus forcing the rad fans on any time the AC is on. The AC got cold and stayed cold. I'm still only seeing temps down to 10-12 degrees, but I'm real close to getting this nailed... I can feel it. And the difference is, forcing the fans on now keeps the system cooling well in town.

Ideally, I really do think a better condenser and/or optimized fan cutoff switch for this system is the best idea. But what I'm going to do, I think, is wire a manual override switch for the fan cutoff. That way, if I'm driving in town, I can force the fans on and get good performance in town and yet keep the system stock for highway driving when enough air moves through the condenser without the fans running.

At any rate, I just got back from the post office. 28 degrees Celcius, humidity over 90%, and the system was cooling almost as well as R12 used to in this car. Same story yesterday in 30 degree temps. It really is possible to get decent performance out of HC-12a and the Nippondenso 6C17.

All I need to do now is tweak the valve a little more, confirm that the system still performs decently well in over 30 degree weather, and I can close the books on this one.

Incidentally, I found a great resource for variable displacement compressors. Thought I should link to it here, though it's more about GM compressors than this one:

http://www.aircondition.com/tech/getattachment.php?data=NTN8UmVmcmlnZXJhbnRfQ29udHJvbF9WYWx2ZXMucGRm
 

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Change of plans for today... I will still try to drill the adjustment access hole, but all I will likely end up doing today is a minor tweak to the main control valve, setting it to about 1/3 turn CCW. No more refrigerant will be purged.

I believe I found the key to unlock HC-12a's performance in this car. I suspected the fans don't run often enough in the default configuration. The fan cut off switch is looking for R-12 pressures, and not seeing them as often. Therefore the fans run less often. Therefore, the system doesn't perform properly. So, what I did on the weekend was I went out there and jumpered across the fan cutoff switch connector, thus forcing the rad fans on any time the AC is on. The AC got cold and stayed cold. I'm still only seeing temps down to 10-12 degrees, but I'm real close to getting this nailed... I can feel it. And the difference is, forcing the fans on now keeps the system cooling well in town.

Ideally, I really do think a better condenser and/or optimized fan cutoff switch for this system is the best idea. But what I'm going to do, I think, is wire a manual override switch for the fan cutoff. That way, if I'm driving in town, I can force the fans on and get good performance in town and yet keep the system stock for highway driving when enough air moves through the condenser without the fans running.

At any rate, I just got back from the post office. 28 degrees Celcius, humidity over 90%, and the system was cooling almost as well as R12 used to in this car. Same story yesterday in 30 degree temps. It really is possible to get decent performance out of HC-12a and the Nippondenso 6C17.

All I need to do now is tweak the valve a little more, confirm that the system still performs decently well in over 30 degree weather, and I can close the books on this one.

Incidentally, I found a great resource for variable displacement compressors. Thought I should link to it here, though it's more about GM compressors than this one:

http://www.aircondition.com/tech/getattachment.php?data=NTN8UmVmcmlnZXJhbnRfQ29udHJvbF9WYWx2ZXMucGRm

I wonder if there would be any harm in just keeping that fan pressure switch jumpered all the time? In most of the other early 90's cars (with fixed displacement compressors), the fan comes on anytime the AC compressor comes on.
 

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Discussion Starter #44
That's what I was wondering, too. My fans ran pretty much all the time with R12, anyway. Figured though maybe I could extend the fans' lifespans by letting the system go back to normal for highway driving. But I may end up just leaving it jumpered like that, depending on whether or not I can find a switch somewhere in my electronics stockpile or I get lazy enough to decide I don't want to run wires.

I get the feeling that even though my vent temps aren't getting meat locker cold yet, I probably won't see them deviate too much when the really hot weather starts. As long as air is going through the condenser, the Duracool should still perform as well as it is now, unless the main valve is really off or something, and I don't think it is. I might try setting it back to default once and see what the difference is vs. when it was overcharged, but I expect that won't improve performance any.

Also scheduled for today is an ignition switch relay bypass for the blower. My bottom steering wheel cover is getting uncomfortably hot to the touch - I need to redirect some current flow or risk having to replace the ignition switch again, the harness, or both. Hope I can find all the parts I got for that once upon a time.
 

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That's what I was wondering, too. My fans ran pretty much all the time with R12, anyway. Figured though maybe I could extend the fans' lifespans by letting the system go back to normal for highway driving. But I may end up just leaving it jumpered like that, depending on whether or not I can find a switch somewhere in my electronics stockpile or I get lazy enough to decide I don't want to run wires.

I get the feeling that even though my vent temps aren't getting meat locker cold yet, I probably won't see them deviate too much when the really hot weather starts. As long as air is going through the condenser, the Duracool should still perform as well as it is now, unless the main valve is really off or something, and I don't think it is. I might try setting it back to default once and see what the difference is vs. when it was overcharged, but I expect that won't improve performance any.

Also scheduled for today is an ignition switch relay bypass for the blower. My bottom steering wheel cover is getting uncomfortably hot to the touch - I need to redirect some current flow or risk having to replace the ignition switch again, the harness, or both. Hope I can find all the parts I got for that once upon a time.

Installing a relay for the inside blower is a wise move. Chrysler omitted a relay for the blower on certain models (including both my 91 vehicles) and I have burned up a couple of ignition switches and still have a small melted hole on the bottom right corner of the steering wheel trim shell on my Spirit. Apparently as the blower ages, it draws more current (probably bearings drying out) and the ignition switch contact can't handle the additional current without getting hot.

Regarding the fan on/off switch that you are considering..... just be sure to leave the fan pressure switch in parallel with your mechanical switch because if you accidently forget to turn on the condensor fan, you will damage the compressor and possibly blow out a hose or operate the pressure release valve on the drier (if equipped). Personally, I'd just leave a jumper around the pressure switch so the fan operates anytime the compressor is running. The additional wear on the fan will be insignificant in my opinion.
 

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Discussion Starter #46
I'm all done for the day. The bracket did not get drilled - it's just too hot and humid out there right now.

Bypass relay for the blower worked like a charm... the underside of the column now stays nice and cool, while the blower seems to run faster. It's a new blower, so it shouldn't be drawing too much current, but all the same I do hear a difference. The relay is a 30A unit with a 30A fuse in the wire in front of it.

I ended up just installing a permanent bypass jumper wire for the fan cutoff switch. I'd had enough of the weather by that point.

Valve is now at about 1/3rd turn CCW. Highway vent temps were fine, but in town and idle temps have gone up. I get the feeling I need to set that valve back to the default, or turn it clockwise now. Highway performance was actually quite acceptable... it is now 35 degrees out there (93 Fahrenheit), and my vent temps went right down to 10 degrees again. The ATC never slowed the fan down much, but the AC is working acceptably well even in this weather. In town, vent temps went back up to 15 degrees. Compressor sounds a lot happier - no noise at all from the clutch.

All in all, I'm happy with the system as it is. Just need to finally get that valve setting nailed down.
 

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Personally, I'd have wired the fan the way my car is: when the A/C relay closes, it cascades and closes the fan relay, so the fan is always on when the A/C is on. That way, the low-pressure cutoff switch still protects the system.

Will check into the blower wiring and see if mine gets hot. I haven't had a problem yet in almost 20 years of driving a gen 3 Daytona, but I never looked for it. That would be a good solution.

I'd be interested in how R134a would work for you. In my 93 Daytona with 2.5L TBI and a 10PA17C compressor, I'm getting a vent temperature of 40F (4C) at ambient 85F (29C).
 

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Discussion Starter #48
Wiring diagrams for the car shows that the fan cutoff switch doesn't affect the low pressure or high pressure switches on my car. All it does is complete a ground circuit at the rad fan relay when AC high side pressures go too high.

But maybe I don't want that... this raises the possibility the fans could come on when I don't want them to. Hmm... I still have 30A relays left over. Wouldn't be too hard to rig something up so that the bypass only works when the compressor clutch gets power.

Edit - yeah, I need to go wire another relay. The bypass puts the fans on with the ignition, regardless of AC operation.
 

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I guess I don't know what this fan cutoff switch is. I thought that you jumpered out the low-pressure cutoff switch, but I must be mistaken. But what I proposed was a relay whose coil is energized by the load side of the A/C relay, so that the fan relay is closed the entire time the A/C relay is closed.
 

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The pressure switch turns on the electric fan when the high side AC line pressure reaches 160 psi. I'm not sure why they put that extra switch in there just for that purpose since many of the other cars turn the fans on immediately when the AC compressor clutch relay closes. Perhaps it is to stagger the loads so that not everything starts at the same time, which might cause the voltage regulator to overreact (i.e. voltage surge/sag effect).

I notice my 96 Voyager is the same way. The fans come on about 10 seconds after the compressor starts. All my older cars had the fan start up immediately when the compressor kicked on.
 

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Discussion Starter #51
I think the cutoff switch is to assist the variable displacement compressor in regulating AC pressures, but I don't see why it's necessary either. Perhaps it's there to help more with the perception that these are quiet running cars by keeping the fans off as long as possible. And yet the solenoid pack is loud enough to wake the dead, go figure.

Just call me Relay Man:



Had the TCM help me out with mounting it. It's grounded where the harness is grounded, which incidentally needed cleaning up. So, I did that too.



Used quick splice connectors on all three wires. It was either that or mess with the soldering iron and heatshrink on an already too hot day. The relay activates when the compressor clutch does. Works perfectly. The relay itself is identical to the one I used on the blower. Got it in a five pack - I think I have a couple left yet. Used three on this car alone. One on the AC, one on the audio system, one on the blower. I want to install one more to enable power windows in the accessory key position, but that's a later project.

It is unbearably hot out there. I sense ice cream in my near future.
 

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Discussion Starter #52
Oh, I'm on to your tricks now, mister master control valve...

Today I set the valve back to default. Not easy, it tends to fight clockwise adjustments, but I did it. I then disabled the relay mod temporarily to see what the system did at total stock settings. Temps at idle standing still were outside - 27 degrees Celcius, vent - 18 degrees or so. I then went and kicked the fans back on. Almost immediately, the vent temps went to 14-15 degrees. Went for a drive... two blocks down, and the system was already doing 11 degrees in town. Got out on the highway, and never saw lower than 10 degrees or higher than 12. And I only saw 12 when I slowed down to turn around.

So the system is once again working better than it was since the last adjustment. And I now know exactly how to adjust that valve. Clockwise increases refrigerant flow through the compressor according to RPM. Counter clockwise decreases it. Getting the system to get its absolute coldest temps may yet require clockwise adjustment - I might do it, I might not. See, the system is already working well enough now I could live with it. I had the car on the highways for decent length trips twice last week, and the system really performed well both times I thought. Of course, the next really hot day may change that, but I'm thinking I'll still see the same 10 degree or so vent temps on the next 35+ degree day, too, just from what I observed last week when it was that hot.
 

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Discussion Starter #53
Had an interesting conversation with my brain this morning. Thought I should recap it so others can learn things, and/or be amused.

"Hey, self. Say, do you know how an AC system works?"
"What kind of question is that, brain? Of course I know."
"So... you're aware that for proper functioning, proper airflow must be seen through two specific parts, right?"
"Yeah, I know. The condenser and evaporator. What's your point?"
"Well... you checked the condenser and fiddled with the fans... did you check the evaporator too?"
"Uh... yeah... so?"
"When did you last check the evaporator?"
"You know, I don't think I like your tone."
"When. Did you. Last check. The evaporator. Humor me."
"Hmm... you know, I think it was probably a couple years ago."
"Check it again. Now."
"Sigh. All right. I'll pull the power module, and... wow, look at all the leaves! I can't be-leaf this! Haw haw haw."
"You're a funny guy. Now fix it."

Yes indeed, in only two years, it seems my evaporator built up enough dirt, leaves, and feathers to build up a small tree farm. Or an aviary. There was a dead moth in the power module heatsink. So, I grabbed the vacuum cleaner, got in there, jammed my hand up to the wrists in the air box, and commenced to cleaning things out. Had to stick a small paint brush in there and use the handle to clean out most of it, which was trapped way back beside where the power module mounts. In all, I would say about 10-15% of the evaporator was full of junk. It took about two hours to clean it all up, and I still didn't get all of it.

The evaporator itself has some surface rust in places, so it could be I'll be replacing it one of these days (will get the heater core done at the same time), but for now I felt encouraged that perhaps I'd pick up a little more performance from the AC. Onto the highway the car went.

Vent temps stuck to the 10 degree Celsius mark again until I turned around and headed back to town. Then, it hit 9 degrees (47 Fahrenheit) and stayed there. At no time did it go higher than 11 degrees on the highway. I do believe it's working better, and I do believe I'm happy with that extra one degree lower. The system had no problem cooling off the cabin at 25 degree outside temps.

The moral of the story? Just because one finds a leak at the low side valve doesn't mean there aren't other problems to find ;)
 

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This is what my evaporator looked like on the 91 Spirit when I changed it out due to a leak. It is probably full of crap again 7 years later and I believe I have to remove the blower to get a vacuum hose in there.

 

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Discussion Starter #55
Yikes - that one's worse than mine... slightly.

I almost wonder if it would be worth it to fabricate some kind of access panel around that area for easy cleaning. But I do have the power module opening to help out... doesn't look like your air box has that.

I was actually tempted to pull the blower out to get at some of the leaves I couldn't. At any rate, I probably should have wrestled the shop vac out of storage rather than using the house vac. But it did the job anyway.

What gets me is that many of the leaves in there were big ones. There's no other explanation - all this stuff must have come in back when my cowl drain was plugged on that side.
 

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Discussion Starter #56
Necropost for a second year update. Got through 2012 just fine with the system as I left it two years ago. Worked pretty well.

This year, it's iffy. Particularly today, when I had it out on the highway in 30 degree Celsius weather. It had real trouble to the point that anytime the car came to a stop, rad fans or no, all I got at the vents was 19 degrees Celsius. Terrible.

So, I get under the hood and pull the cap off the R134A low side adapter fitting. Pssht!!! Turns out that when tight, the cap actually pushes the valve stem down. Head -> desk. Wham! Wham! Wham!

Lucky me, I now have a known leak in the system again. I'm going to have to evacuate the whole thing and try to gas it up from scratch again. I hate this idea, because I now have to play "guess where you should stop charging" with that awful variable displacement compressor again. I also need to MacGyver some kind of cap solution that won't let all my refrigerant out.

Fortunately, I now know to keep the rad fans running while charging. Unfortunately, I've decided against Duracool this time and will be going to one of the other (70/30 instead of 60/40) HC-12A blends. This may work better, it may not. But because I only know how the system responds to Duracool, I'll be guessing my way to a proper charge all over again.

How I loathe the 6C17 compressor. I am this close to ordering an AC delete bracket and pulley for this car. I'm getting into storm chasing soon, and will hopefully have a 3G or 4G minivan for the summer months starting next year. The Imperial can be my winter car, and I don't really need AC much in winter. But even if there's only a small chance I can get the system working well enough again, it's still worth a try methinks. I have thought about trying to find fixed displacement system components to retrofit, but that's going to cost some dollars, I reckon. Dollars I don't have, even if I do find a fixed displacement compressor that will bolt to the 3.8, and all the parts that will need to go with it to make it work with the ATC. Likely, I'd be looking at swapping everything involved with the AC to do that.

I did try a small top up charge today using the leftover HC-12A from my sister's Kia Sedona retrofit. It already had the system cooling a bit better on the highway, but not by a lot. I got 15 degrees C at full fan, 13 degrees at half fan, and 11 degrees at quarter fan. Back when I first did the retrofit, I got down to 8... that's what I'm aiming for again. Vent temps were unchanged standing still with the rad fans on.

Meantime, that Sedona is giving me 11 degrees standing still, 6 degrees on the highway. I wish the Imperial could do that.
 

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I can understand the desire to pull the AC, but even in winter having working AC makes the car a much nicer place to be. It sure helps the defrost work better.
 

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Discussion Starter #58
That's definitely true. Also, on this car, the AC smooths out the engine below 40 km/h... it tends to shudder when driving around that speed. There's a TSB on that issue that calls for an updated ECM (PN #4762740), but I'm too cheap to do that. They're impossible to get used. There's no shudder problem at all with the AC on, so I ignore it during the couple months of the year or so it's an issue.

With regards to the cap, I think I'll just drill out the center and maybe glue a bottle cap liner on top. That should fix that issue.
 

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I don't quite follow why you need to drain the entire thing. Why not just fill it until the air coming out is at the correct temperature?
 

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Discussion Starter #60
It's been sucking in air again, I think, due to the cap pushing on the valve. That's why it won't cool standing still, and may be why it's bogging the engine down again at times. I need to be sure only refrigerant is in there.

Also, because there aren't many people trying to use the hydrocarbons on the 6C17, which only works properly with R-12 and nothing else, there's not a lot of prior experiences I can go by to determine where to stop for the proper charge. This compressor keeps low side pressures steady, even on a low charge, so you really have to charge by weight. Hard to do that when you have no idea what's currently in there. This would be hard even with a full set of manifold gauges, which I still cannot afford. I can watch low side pressures with the fancy charging hose I picked up in the US a couple years back, but that's all.

Speaking of which, current low side pressures are pushing 50 standing still, 30 when the engine revs. 50's at the very top of the "ok" section, 30's at the bottom. It did better numbers than that when I first installed the Duracool. With the engine off, the gauge buries the needle at 100, telling me the system is pretty well at or over capacity. That's how I figure it's likely been pulling in some air. Adding more HC-12A right now would just be a waste of refrigerant.

Fortunately, most of these HC blends are sold with each can containing almost exactly a half charge of the stuff for this car. That's what I'll do this time... two full cans only results in a very slight overcharge. I'll then know even if two full cans go in from empty, it should not be overcharged enough to cause issues. But there are no guarantees with this compressor, so we'll see.

I'll report back to this thread for future reference when I have some cash to go get the new refrigerant. I do plan on disconnecting my rad fan relay to see if the system works normally without it, but I'm betting it won't. There's still the off chance that the control valve in the compressor is defective, as well. I should have swapped over the compressor from the 1991 Fifth while I had the chance - I know for a fact that one was working fine :(
 
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