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anybody ever heard of one of these?

boatmoter on Fri August 10, 2007 8:10 PM User is offline

Country of Origin: United States

Anybody ever heard or seen a kit to install on a a/c system that has a senser to install on to a evap and hooks to a switch to kill the compresser when the evap gets too cold?? sort of like a handa or toyota, but without the module and all the wiring.. looking for a quick and kinda cheap fix for a evap iceing problem.. ices up if you don't run the fan on med hi or hi. you guys already give me some tips on dianostics,but I would rather just do a quick fix,car has 200000 miles,a/c is around 3 yrs old,but don't want to invest lots of time into it..

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Glenn //

TRB on Fri August 10, 2007 10:19 PM User is offlineView users profile

There are preset thermostats and rotary dial thermostats available. Power in - power out - can't get any simpler than that.

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JJM on Sat August 11, 2007 12:18 AM User is offline

Just like in the olden days...

In the days of old,
When night were cold,
And toilets weren't invented,
So they dumped their loads,
Along the roads,
And walked away contented!

... now where the heck was I... oh that's right, you were asking about a thermostatic switch. Is this what you're talking about?



It's a typical thermostatic switch I haven't seen in ages. Nice thing was most them had separate cut-in and cut-out adjustments. Set them a little too close, and the compressor would cycle rapidly. So in the olden days rapid cycling didn't mean low charge, it meant improperly adjusted thermostatic switches! How times have changed... in the days of old... ahhh, nevermind.

A part like this might be difficult to find through normal channels, so why not just go for a low pressure switch and mount it on your low side service port, just as simple and it'll accomplish the same thing nice and cheap. Tim should be able to get you one.

Joe

When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com




TRB on Sat August 11, 2007 12:22 AM User is offlineView users profile

Joe we have them in stock and use them all the time in our aftermarket systems.

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

NickD on Sat August 11, 2007 7:08 AM User is offline

Even I living out in the woods have heard of those thermostatic control systems, while Joe is recommending a cycling switch that work quite well as the cavemen have shown us a strong relationship between pressure and temperatures in refrigerant systems, they only work in fixed orifice systems. They don't work very well in expansion valve systems as when the evaporator cools down to the freezing point, they close, keeping the low side pressures up so the evaporator can freeze up. Always a tradeoff in whatever you try to do.

You really don't need one if you are bolted to a seat with a vent blasting in your face, the air gets a musty kind of odor and starts to slow down, when this happens, just slide the climate control from AC to vents and when the air feels blasting again and warms out, slide that lever back to AC. The one in my motorhome had an exceptionally long capillary tube, like 27" long and whatever was in that tube to put pressure on a diaphragm had long evaporated poking holes in the ozone layer and killing penguins.

The contacts were permanently closed and were in series with the compressor clutch. I posted a picture, Bohica was kind enough to find a site with a picture of the one in mine, but no place to buy a replacement, Tim was kind enough to give a .pfd of his stock, couldn't find anything close with that very long capillary tube. Could have said the heck with it as strapped in the seat anyway, but had parts laying around so rolled my own.



Needed to convert temperature to a voltage, so put ten 1N914 diodes in series, a dab of expoxy on the exposed leads and put those in a 1/8" diameter 6" long brass tube stuffed with thermoconductive compound and sealed with expoxy at the ends with plenty long leads on it. Tossed that in my chamber and recorded the voltages at about 33*F where I wanted to switch off the compressor and about 39*F where I wanted it switched on again.

Old switch had 12V coming from the climate control with the other side of the contact going to the compressor, used that 12V not only to fire up the compressor, but to power this circuit as well, just had to add a single ground lead, put the circuit in the old thermostatic box as holes were already drilled for in on the side of the evaporator box. A common LM741 would work for the comparator amplifier, but had chopper stabilized TSC911's laying around that have zero offset drift. Hysteresis could have eliminated Q1 in the circuit with comparator feedback, but this is the most accurate means to obtain precisely 6*F of temperature differential. The 7808 gives a precise reference for the comparator, the TPI2955 replaces a relay with direct solid state drive, and R3, a ten turn potentiometer lets me precisely adjust the drop out temperature. R5 could have also been a pot for the differential, but 5-7 *F differential is close enough and far closer than trying to click a spring loaded switch with a pressure diaphragm. Sprayed the circuit with MFR to make it moisture resistant, works very well and gives me one less thing to do when driving, now I have nothing to do except steer and maybe even watch the road now and then.

Entire circuit could be put in a chip and manufactured in China for less than a couple of bucks, use to do stuff like this, ha, just had to learn if I could still do something like this. All this circuit does is switch off the compressor if the evaporator temperature drops below 33*F and will also do that if the ambient drops below that as well, switches it back on again if the evaporator hits 39*F and stays on at any temperature above that point.

Could have added an LED to the dash, but with a York, don't need that, unless I get stone deaf. You are welcomed to use it if you like.

boatmoter on Sat August 11, 2007 11:31 AM User is offline

sounds good tim,can it screw in place of the o.e. one on the low side line?? I went to the arizona web page and it looks like they have 4 different ones,2 say they are compresser mounted,the other two who knows, do you know which one it would take? Im getting ready to order a pf condenser from them and would want to get the switch at the same time.

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Glenn //

TRB on Sat August 11, 2007 12:40 PM User is offlineView users profile

What are your looking at on our website as these do not hook to any line? The thermostat has a probe which is inserted into the evap core. You can mount the thermostat anywhere. A power lead goes into one side and the other runs to the compressor clutch.

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

TRB on Sat August 11, 2007 12:57 PM User is offlineView users profile

Here is the link to many itewms we have avaailbale and are not listed on our website.

http://www.ackits.com/additional/main.htm

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

mk378 on Sat August 11, 2007 2:02 PM User is offline

You can pull one out of an old Honda Civic, before 1992 they used (rather noisy) two wire mechanical switches, 1992 to 1995 and probably beyond they had a three wire electronic similar to Nick's circuit but it switches to ground and is only good for relay coil current, won't be able to drive compressor directly.

boatmoter on Sat August 11, 2007 2:30 PM User is offline

well Tim,what I thought you were saying was replacing the clutch cycling switch on the high side line,the oe screws on with two wires attaching. I was kinda figuring the part you were talking about was like the oe,but with a different pressure setting.. the pic you put up looks like a thermostat control switch..

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Glenn //

boatmoter on Sat August 11, 2007 2:40 PM User is offline

Tim,on the preset thermostats, how do they come? does each preset thermo have the same preset temp setting?if not which temp setting would you recommend ?

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Glenn //

TRB on Sat August 11, 2007 2:50 PM User is offlineView users profile

The preset are preset from the factory to cycle before the core starts to freeze. Somewhere in the range of 33 degrees. I do believe they have set screws to adjust if need be. Been a while since I check on and you never know when a vendor does a chance. I'll look Monday for you.

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

NickD on Sun August 12, 2007 7:19 AM User is offline

From what I recall with my older Cadillacs, Hondas, Nissans, and Toyotas, all would open at 33*F then have to warm up to 39*F before the pressure switch would close again. Pressure switch is very similar to what you would find on an air compressor. Some were adjustable, one screw would set the low drop out temperature, the other was for hysteresis, but the two were interactive in that adjust one, it would screw up the other, so had to go back and forth several times, time consuming when doing this on the vehicle.

I have had problems with these in the past, a mechanical contact that would either stick or not make contact, contacts were always buried underneath the springs, so the only way to clean them was to take it apart, would count screw turns so I would get it close when putting it back together. Never had problems with the capillary tube, diaphragm would always go down when the tube was cooled. Figured the contacts in the motorhome thermal pressure switch were stuck together as they directly switched the compressor clutch coil, but time caught up with me and the diaphragm wouldn't even move a micron with drastic changes in capillary tube pressure, said a dirty word.

powerflite on Sun August 12, 2007 7:14 PM User is offline

My old aftrmarket system with expansion valve and cycling clutch used this type of evap. switch mounted in a big block of rubber. Worked just fine. Even better is the thermal cycling switch mounted in a thermal well at the outlet of the evaporator. Response is almost instananeous when the liquid refrigerant hits it.

NickD on Mon August 13, 2007 9:03 AM User is offline

I feel it's pretty good when you have an evaporator that can freeze up with 120*F humid air passing through it at 500-1000 cfm. Too bad the only solution seems to switch off the AC system when freeze up starts to occur. Old Mitch reported getting close to 0*F vent temperatures by bypassing the thermo cut out, but he lived in a very dry dessert climate.

Maybe we need a dual evaporator system with the first acting like a dehumidifier to get rid of some of that moisture. Wife asked why there was a huge puddle of water under our car after we stopped at a rest area, surprised you never noticed that before, but that's why I ask to switch off the AC about six blocks before you come home with the blower on max, or else we get that huge puddle of water on the garage floor. Plus it doesn't help the evaporator to be soaking wet all night.

What a day, yesterday, my last aunt died at 95 and I had to attend the funeral, had to drive south and completely forgot about Illinois traffic on I-94, but we left at noon and normally not that bad. Under if the interstate designers ever figured out that combining I-90 and I-94 at Tomah is putting four lanes of traffic on two? We made good time driving down there, but stopped dead. And recall driving north when this traffic was blocked clear from north of the Dells all the way down to Chicago. Got off the interstate as soon as I could, but guess these Illinois people are also getting smart as they also knew about every backroad I thought was my secret. Took us over 2 1/2 hours to travel the last 30 miles, but at least on the backroads the traffic was barely moving, we arrived over an hour late.

Expected to see a couple of hundred of my relatives, they all live south, but only about two dozen showed up, but they had to drive south, good luck. We flew home, but glad I wasn't driving south. Wife is a large city gal, and would like to move down there, but couldn't help making the comment, millions come up here to see trees and get away from the crime in the large cities, can't blame them.

You would think after 50 years, someone in the DOT would figure out that 2 + 2 = 4, not 2.

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