samiam4

Good morning,


I'm wondering on whom will help with this? The factory service manual isn't very detailed on the performance of the cycling switch. Some have just removed them from the circuit, but I'd rather tweek the range.

Here it goes- the probe is a some sort of thermocouple/thermometer. The resistance varies at various temps- factory has set it conservatively so you should never freeze the evaporator. I read this as :
1) low freon
2) low airflow
3) high humidity
4) low temp..

I know from some other car manufactures, conservative could be about 42-45 F. Ours FSM states that it must cut in by 45F or replace.

So, I've taken some resistance readings
42 F 5.5 K ohm
95 F 1.3 K ohm
81 F 1.8 K ohm
72 F 2.3 K ohm

So we just add a large resistor in parallel with the current probe to trick it. So, the probe reads say 35F, and the relay thinks it's 40 F.

So, if someone has a truck- which is working properly ... cold vents 40-50F, please measure the cut-out temperature (when the compressor kicks off). You can use a lowside pressure gauge- just let me know the pressure(and freon type).

I'm going to start with 47 K ohm.

Michael

samiam4

Oh,

my guessing education is based on ... mechanical cycling switches were 15-30 psi, via the internet ETR's are ussually 25-44 psi. So, I'm just trying to tweek the system to the low-end of the scale.

M

wannadiesel

Or just pull the probe out of the tube until you get the results you are after...

samiam4

Humm never thought of extending the probe!



I've got a 47 k ohm resistor added that means at 35F, the relay thinks it's 42F.

About how far out did you pull the sensor. There you are balancing outside temp vs liquid line. Seems like adjusting with a resistor is better.


Michael

Michael

TJE

I'd sure like to see how this turns out....when I pull the probe out...or when I push it back in....no matter how small the increments it goes from one extreme to the other. Either 50* or 15*

Good luck.

92roughstock

I'd love to have 15* air. Heck, I'd settle for 50 right now. My fiance said at her shop, they consider a 30-35 deg drop from ambient to be really good, but that is the newer R134A systems, not our old R12s. I have a leak I need to find and fix first.......