Automotive Air Conditioning Information Forum

Tim - I posted the following previously on his Facebook inquiry, so re-posting here so members on this site could can comment if desired. On his truck, the air path goes from inlet to blower fan through evaporator so is before the heater box. So the only source of heated air at this point getting in would be from the intake "door" being open to the outside fully; but in that case the evaporator sensor would stay on longer as would be higher temperature.

If mine, there are several options I might explore.

1. Test your switches in cold water baths using a digital thermometer. These switches are contact switches designed to be "open" at about 35F and to "close" a few degrees above that to complete the circuit and engage the compressor.

2. Pull the sensor line out a few inches so its in a less-cold region of the coils, or just sitting in the evaporator box.

3. Install a toggle switch in place of the evaporator switch/de-icer switch and just use the AC push-in button to switch off the compressor if the temperatures get too cold or switch off every few minutes to allow any ice to melt and condensate to drain.

4. Bypass/jump the evaporator switch/de-icer switch and just use the AC push-in button to switch off the compressor if the temperatures get too cold or switch off every few minutes to allow any ice to melt and condensate to drain.

5. On my B2200 and 1998/2004 Frontiers, if the cabin gets too cold (yes - I'm in Arizona desert) I simply push in the AC switch to turn off the compressor for a couple of minutes, then push it in to re-engage the compressor as needed; I don't add in heated air to temper the air temperature. In your part of the country you don't get as hot as Arizona, but you have more humidity, so cycling it off manually is easy and should work for you. I do that on ll three of those trucks.

6. Run a indicator light on the dashboard in parallel to the compressor wire so you can be positive that the compressor is not getting power when the cooling stops. I have such indicator lights rigged up on both my B2200 and my 1998 Frontier; last summer I used that light on the Frontier to diagnose AC clutch slippage on it, and removed a shim under the clutch drive plate to fix it (didn't even need to remove the AC belt or compressor to do that !!).

7. Try an adjustable switch, especially if the stated range is lower than 32F.

Its legal in all states except these.

Arkansas, Arizona, Connecticut, Florida, Idaho, Indiana, Iowa, Kansas, Louisiana, Maryland, North Dakota, Oklahoma, Texas, Utah, Virginia, Wisconsin, Washington, and the District of Columbia.

Luckily I do not live in any those places.


The legality lies in that you have converted to R134a first, but still there are some states that are too stupid to realize is the safest refrigerant out there. 100% ozone friendly, better performance and safer than other refrigerants.
Out performs R12 and since my truck is meant to run R12, I rather go with this substitute.

I have ran R152A, R134A and for a long time, Duracool in these trucks.

http://www.duracool.com/-faq.html

Cusser, I am still going to do some more testing,, the verdict is still out.
What I find odd, is I am really pretty good at installing and maintaining AC in these trucks.

It is a really simple system.

I find it strange that:

1) I now have two possibly defective thermoswitches all of a sudden, thats just odd to me, but me fiddling with them could have damaged both that I had.

2) I may or may not have had a bad expansion valve, replaced it anyways.

I feel pretty certain my charge is appropriate based on experience and relative temps, and the gauges. Also duracool is just as forgiving as R12, not like 134A.

It works great other than cutting off too soon.
It has always cut off at the appropriate temp which is usually 38F or even a bit colder at the vent temp, sometimes at 40-41F
This is how it works in all the other trucks I have done including this one until I changed out the evap.
This lets me know the thermoswitch is doing its job, but cutting off at 33.8F at the core.

This is why I am leaning toward a bad thermoswitch.
When I bypassed it, the temps went down to 35 before I cut it off manually and I had no frost at the vents, and plenty of air blowing from the blower on speed 2.

Why after all these years we still have to debate this issue.

https://www.epa.gov/snap/unacceptable-s ... frigerants

Its not an "issue" really.

Its always about Money.

The latest most expensive thing out there is R1234YF and its more flammable than duracool.

Its crazy. Used overseas all the time and in the USA.

digeratimvp wrote:Its not an "issue" really.

Its always about Money.

The latest most expensive thing out there is R1234YF and its more flammable than duracool.

It's crazy. Used overseas all the time and in the USA.

R1234YF has a completely different system design. So what if it is used in other places. The point is and always will be. It's not a legal refrigerant for R12 replacement in the US.

If you want to argue the point. Find an HC12 site to make your claims. I've dealt with this for 20 or more years now. Not willing to have the debate again.

You can delete this entire post if you want.

digeratimvp wrote:You can delete this entire post if you want.

No need for that. Just saying we have enough miss information these days. HC12 is not legal for R12 replacement in the US. Try to understand, we have had this debate for so long. It gets very old after a while.

Ok back on topic, these were the readings at noon today.

12:00PM
85F outside, I was in a covered garage that was not in the sun felt like 78-80F

Pressures at 1500rpm:
35 Low
225 High

With box fan in front
30 Low
200 High

So my thinking is the (new) Expansion Valve (bulb type) is ok.
There is sweating on the low side line going all the way to the compressor and its 60-61F at the outlet of the evap at the firewall, using a infrared thermometer.

Using same thermometer, its about 145F at the high side of compressor, then at the bottom of condenser about 125F and 114 at the top of it.
Then as it goes into the drier, its sometimes 95F to 105F on each side of it, (in and out) and sometimes its 114F.

The high side going into the firewall into the evap is about 95F.

I am trying to determine if there is still an exapansion valve issue, or if its simply the thermoswitch, or have I missed something else?

I am kind of leaning towards taking it all apart AGAIN, and putting in the expansion valve that was working on it to begin with.

digeratimvp wrote:When its bypassed, it gets the vents down to 35F, of course because its freezing down there.

I personally would not monkey again with the expansion valve or the refrigerant charge, as great cooling occurs if the switch is bypassed or is "closed". I'd focus on the thermo switch which needs to close more often, or do some sort of bypass.