Our AC system SUCKS

That is a Weber thermometer from the BBQ section at Lowes

 

Very nice thank you!

 

10-4 I expect to get different readings depending on outside temp and humidity and whatever else rain etc. but my A/C was climbing to 60 degrees while I was sitting at a red light or a drive through waiting for a burger

 

The original post and the fact that I was having a rise in temp at idle and the fact that other owners were having the same issues is what made me add the fan. I feel my posts in this thread speak for themselves

 

Mine was going anywhere from 60-70 at idle in either a drive through or extended idle in 90 degree plus heat.

 

Thank you sir

 

Sorry I asked God but he would not raise the temp in Georgia today just for me to test my A/C system.

 

I will re do and post my results when it is above 90*

 

10-4 My post was as much as i could do with all the rain we have been having, I have been more in a conversation with @anthony250f and @TXpro4X4 and I was just trying to let them and others who have went to the trouble of adding a electric fan to know my results.

 

I added a fan, too.
















EDIT - Forgot this one:

 

DUDE!

Make me one!!

 

I don't think I want to do that EVER again, lol. A week later and I'm STILL finding aluminum shavings in my shoes.

 

Fine. Don't do it for me. Lol. Yeah no I get it man. Shavings of any sort are just not cool at all!

 

I did a little experiment with the evaporator temperature sensor today.

Ambient temp here today is about 80*
Truck idling
A/C ON
Temperature dial set to max cold
Fan dial on speed 4

I put a digital cooking thermometer into the center A/C vent.


I closed the doors and let the truck sit there running for about 5 minutes, then hopped in and watched the thermometer while listening for the compressor to cycle off. I let the compressor cycle off and on a few times to make sure the result was consistent. Compressor cycled off at 50* and back on at 54*.



Armed with this measurement, I set out to try and trick the A/C amplifier to keeping the compressor on until a lower temperature. This is what the service manual says the evaporator temp sensor is supposed to measure. So the hotter the temperature, the lower the resistance.



I measured the resistance of the evaporator temp sensor at 50* and the resistance was 3.45k ohms.

So I set out to fool the A/C amplifier into thinking the evaporator is HOTTER than it is. So I need the resistance to be lower than spec to make the sensor A/C amplifier sees HOTTER. So how do you lower the resistance? You put a resistor in parallel. Care must be taken not to skew the resistance too much because it could cause the compressor to run way too long and the evaporator could freeze up.

I used this calculator.
https://www.calculator.net/resistor-calculator.html

I had this big pile of resistors to work with.



I used the higher end of the 50* range (3.3k ohms) and added different values until I arrived at a number that didn't look too far off, but would land in the hotter range. First I tried a 31.5k ohm resistor.



I installed the resistor in parallel with the evaporator temp sensor and let the A/C run with the doors closed for about 5 minutes observing the compressor cycling on and off. The compressor cycled off at 46* and cycled back on at 50*.



Excellent! I decided to go a little further. Ran a few more numbers through the calculator and decided to try roughly 25k. Didn't have a 25k so I went with the closest I had, which was 26.6k.


This was the result. Compressor cycles off at 42* and cycles back on at 46*. So I just made my A/C blow 8* colder than it was before! Naturally, I'd like it to get all the way down to 33* but keep in mind that I'm measuring temps at the vent, not at the evaporator itself. The vent temp is naturally going to be a few degrees warmer than the evaporator due to the vent's distance from it. I don't want the evaporator getting too cold and freezing up.



I let the truck sit and run like this at idle for 30 minutes while observing the compressor cycling on and off correctly. Also keeping an eye on the cold side A/C line coming from the firewall making sure its not getting too cold. Everything seems to be working well.

Here is the location of the evap temp sensor harness.


I freed up the harness and soldered about 18" of wire to each of the conductors to make it easier to try the different resistances without having to lay upside down on the floorboard. So currently this is what it looks like.



Im going to drive it like this for a week or so and make sure no issues arise. I think it should continue to work fine, but mod at your own risk!

 

Curiously awaiting the final test results. If this means colder air for all of us having these issues on 90-100+ degree days then this will be a huge win!

 

Well today it’s 80*. I’m curious to see how it behaves when we get back to 100*!

 

Thanks. I may try to get it to a bit lower temp but I want to test this current setup first.

Oh, and I currently get 12.5 MPG, so...

 

As a small update it was in the 90's today out here on my side of California. I pulled the seal off of my cowl and had been running the AC on full blast. Not only did it maintain its very cold temperature inside the cabin through my entire lunch, but it also felt much colder than it previously had. I am actually confident enough in saying that my issue was being caused by excessive heat being trapped in the engine compartment at idle.

I may actually take this all a step further and take my dremel to my hood scoop slit and open up the honeycomb to help further extract heat out of there.

 

I may have to try this.

Also on the hoodscoop, when you take it apart you may find it isn’t as easy as you would hope. I mean you might he able to get some small holes in there but I don’t know how much they would actually help.