AC turns on 1 sec then off. Full charge [Resolved, bad high pressure switch]

Post by **misha** » 11 May 2025, 10:42

When you jump low pressure sensor connector....does the compressor run?
Ac switch needs to be ON and blower must run to test.
Do you have ecc or mcc?

Brickbox8398 · Post by **Brickbox8398** » 11 May 2025, 12:58

misha wrote: 11 May 2025, 10:42 When you jump low pressure sensor connector....does the compressor run?
Ac switch needs to be ON and blower must run to test.
Do you have ecc or mcc?

I have ECC. And yes when I jump the compressor the AC is turned on before I do it. My cooling fan stays on high when AC on my ECC is on no matter if the compressor is jumped or not. So It seems like ECC is “calling” for AC, but something else is not letting the pump run

Post by **misha** » 11 May 2025, 13:20

Does the compressor stay running when low pressure switch connector is jumped or it also runs for one second?

Brickbox8398 · Post by **Brickbox8398** » 11 May 2025, 13:51

misha wrote: 11 May 2025, 13:20 Does the compressor stay running when low pressure switch connector is jumped or it also runs for one second?

It does stay running. Which at least tells me it isn’t the thermal sensor for the compressor itself

Brickbox8398 · Post by **Brickbox8398** » 11 May 2025, 13:55

This is me jumping the compressor and the low pressure reading I get when I do so. I get 30 psi. Ambient temp 70 but also parked in the sun. (I removed the top of the relay so I could squeeze the copper part and jump the compressor). Also ignore the red gage. That is obviously not hooked up.

Post by **Chuck W** » 11 May 2025, 14:04

Could be a bad switch, perhaps?

Also, I didn't see, but did you replace the orifice tube when you had everything apart? You could have a clog.

Also, I'm pretty sure the rad fan should run on LOW when the AC is on and HIGH when coolant temp needs it. With the ECU controls, it's more nuanced than that, but you shouldn't have HIGH fan speed with normal AC operation. However, your high pressure error could be triggering it to HIGH.

Brickbox8398 · Post by **Brickbox8398** » 11 May 2025, 16:57

Chuck W wrote: 11 May 2025, 14:04 Could be a bad switch, perhaps?

Also, I didn't see, but did you replace the orifice tube when you had everything apart? You could have a clog.

Also, I'm pretty sure the rad fan should run on LOW when the AC is on and HIGH when coolant temp needs it. With the ECU controls, it's more nuanced than that, but you shouldn't have HIGH fan speed with normal AC operation. However, your high pressure error could be triggering it to HIGH.

I didn’t replace the orifice tube. I know it is good practice to though…but you’d think if this was clogged then I wouldn’t have cold air when I jump the compressor. And/or I’d have weird behavior on the gauge. You bring up a good point though. It is odd that the fan stays on “WOW” right when I hit the AC button. I don’t remember my old S70 doing that. When I unplug the high pressure sensor the fan goes to low. I am on the verge of replacing that sensor for starters

Post by **RickHaleParker** » 11 May 2025, 21:48

Brickbox8398 wrote: 11 May 2025, 10:32 I purged some charge and I seem to get 25-28psi low port when jumping compressor.

Purge the charge AND the oil. That why your have a clean slate to start. Then you will know how much of each is in the system.

Post by **abscate** » 12 May 2025, 04:32

You can measure the high side with VIDA, good code reader , or monitoring voltage on the three pin high pressure sensor.

You have a combined problem of over pressure and worn out clutch, both have to be fixed.

Brickbox8398 · Post by **Brickbox8398** » 14 May 2025, 16:18

abscate wrote: 12 May 2025, 04:32 You can measure the high side with VIDA, good code reader , or monitoring voltage on the three pin high pressure sensor.

You have a combined problem of over pressure and worn out clutch, both have to be fixed.

I checked for voltage at the high press sensor by carefully snipping the insulation on each wire (I’ll fix this later) and checking with the car on AC “on” (compressor not engaging though) and the connector plugged in. Between 1 + 2, and 1 + 3 I get 5V. 2 + 3 I get .219. I think this is the signal? .1v per 100 psi from my research. But I don’t know if 219 psi is good or bad. Mind you this is with the compressor not engaged but the car running