A/C unit is blowing warm air

Roy,

Tonight I tested the following after letting truck run for a few minutes to allow A/C pressure to stabilize (see attached picture), Freon seems a little low:

Low Side:
0v and 5v
jumped the low side connector, the compressor did not come on.

High side connector:
red = 0v
white=5v
black =0v

I also re-read the air conditioning not working article and am wondering if I have enough power at the low side sensor, the article indicates I need for 12v.

Where should I test next?
Should I add Freon to confirm the low side jump, I read the system needs to be at 25 psi for the test to work properly.

Thank you,
Bret

Roy,

I studied the schematic's further. How likely is it the climate control module is not sending the proper signals to the low side sensor and ECM? Should this be our next test?
Bret

No, the fact the system is working eliminates the sensors and the wiring.

I cannot read the pressure you posted. The picture is too small and cannot make out the readings. Can you either take a picture I can read or just tell me the high and low side pressures?

Roy

Roy,
10-4. Blue gauge = 25 psi, red gauge = 110 psi.
Thanks,
Bret

Okay, how much Freon did you add?

What is the outside temperature?

The low side is perfect.

The high side is low. It should be 2 times ambient plus 15%.

Roy

Roy,

Since I started this project I have added two Carquest 12oz cans and 1-20oz A/C ProUltra Synthetic can of 134a. Outside temperature is 85-95 degrees, we are in Richmond, Virginia.
Bret

The high side should be around 200-205.

With 34 ounces, it should be overcharged.

Do not add that synthetic stuff. Not needed and does nothing.

Just use the standard 134.

Did you add 34 ounces in the system at this time?

Roy

Roy,

10-4 on the synthetic. I added 1/2 the synthetic first several weeks ago before I bought the gauges you recommended. When the gauges arrived, I vacuumed the system down and added 1-12 oz can until I reached about 50 psi and then have added more, as necessary.
Bret

Okay, that is better.

You should have added 1.6 pounds. Do not pay attention to the gauge on the cans. That is not what you go by.

How much do you have in the system at this time?

Roy

Roy,
The last time I added Freon I estimated I was in the 1.5 pound range and I recall you thought the PSI readings were in good shape. The blue is lower now then previously. My July 18th pressure readings were blue = 43 psi, red = 240 psi.
Bret

Correct.

Are you still having issues? Is the air not cold?

Roy

Roy,
The air is cold if I jump the relay but the compressor will not turn on unless its jumped. From what I can tell the compressor and overall system is fine just not getting the signal to turn on the compressor.
Bret

Okay, we will go over this again.

30 and 87 are good for the relay as the compressor comes on when you jump it.

86 has to have power as well.

85 is grounded by the ECM once it sees the correct signal from the low pressure switch and the pressure sensor.

Do you have power at the low pressure switch?

Do you have 2 5 volt powers at the pressure sensor?

Roy

Roy,

I have 5v at the pressure switch and 1-5v line (white line) at the high pressure switch. I believe I need 12v at the low pressure switch and believe that may be the issue.
Bret

At the pressure switch, you need 2 5 volt pins. Do you have that?

Roy,
At the high side, I do not. We expected the ECM to correct this but the results are the same.
Bret

I know I also stated the wiring to the ECM could be the issue. Did you verify the wire was good to the ECM on the wire that did not have voltage?

Roy

Roy,

Do you want me to test the new ECM at pin #14 (ECM to battery ground) and from the high side red line to the ECM (pin to pin)?
Bret

At pin 14 on the new ECM, back probe it and test for voltage.

Roy

Roy,

I tested the following with key in the on position:

1. Back probe with paper clip at pin 14 with harness plugged in 0v.
2. Removed harness, paper clip front of harness, 0v.
3. Pin to Pin - pin 14 to high side sensor red pin - 0 ohms, continuity should be good.

What do you recommend I test next?

Thank you,

Bret

That was a red/black wire correct?

Roy

Roy,
Correct, pin 14 which has a red wire with black line.
Bret

Does not make sense. You have replaced the ECM and it still has no power to that pin. Without that power the control side of the relay will not work.

Roy

Roy,

I agree. This is why I reconsidered the climate control module. I'm not pressing this just thinking through the possibility - if the climate control module is not sending enough power to the low side switch/sensor, I have 5v and per the manual I should have 12v, there is not enough power to send a signal back to CCM to the ECM to the high side sensor back to the ECM to trip the relay and then power the A/C compressor clutch.
Would it work to jump a line from the battery to the low side sensor?
Bret

Roy,
One other thought, I believe when the compressor relay is jumped it's bypasses the climate control computer and powers the compressor clutch.
Bret

No, the power for that wire has nothing to do with the climate control module. It is supplied by the ECM to the pressure sensor.

Yes, correct, jumping 30 and 87 sends direct power to the compressor without the control side of the relay grounding.

Roy

Roy,

Any suggestions on additional tests?
Here's a recap of my test methods, with key in on position:
When I tested the low side sensor - using a multi-meter I touched the red lead to the paperclip in connector and black lead to the battery negative post.
Same with ECM pin 14 test - inserted paperclip in back of harness, plugged harness into ECM, red to paperclip, black to battery negative post
Same process with high side sensor.
Was my test correct?
Bret

Yes, but the issue is nothing at pin 14.

This leads me back to the ECM again. Let me look for any other information.

Roy

Roy,
How do I test the power going into the ECM? See July 11th email with schematic. I believe that's the issue. Pin 14 is line from the ECM to the high side sensor. If you look at the schematic, I would like to test the line from the CCM to the ECM, it's the grey line. I believe I need to remove CCM and back probe the grey line.
Bret

If there was no power to the ECM, you would have many other issues and a ton of codes.

The gray wire you told me had 5 volts as it should. Why do you want to check it again? That along with the red/black need 5 volts.

Roy

Roy,

Agree. I am referencing the white line in the schematic from 7/11 from the climate control module to the ECM. I would like to confirm that line has power with a back probe test.
Should the low side sensor have 5V or 12V?
Bret

You are off track here. The issue is the red/black wire. Neither of those wires have any effect on power to that wire.

Roy

Roy,
10-4. What is the power source to the red/black wire?
Bret

Again, the ECM.

Roy

Roy,
10-4. Should I contact fs1inc and ask for input?
Bret

Yes, see if they can get you some information.

Roy

Roy,

For testing purposes only, what should the voltage be at the white wire exiting the climate control module connecting to SP205 then to the ECM? What is the SP205? Also, do you have a schematic of the climate control module you can send?
Thank you,
Bret

I attached the diagram with the white wire. It is serial data. There is no voltage. It is a multiplexing signal.

Roy

Roy,
What should the readings be at pin #'s: 58 and 43?
Bret

58 is the serial data line I told you about.

43 is the wire from the control side of the relay. It will have 12 volts there unless the ECM grounds that wire. Then it will be 0.

Roy