Air conditioning not working

Midwestdrifter

Engineer In Residence
I will check my van to see what the supply is with the sensor connected.

With the AC off, the sensor should return somewhere between 0.15 and 3V or so. With the AC running is will vary, but probably around 4V or so?
 

alexk243

KulAdventure
I will check my van to see what the supply is with the sensor connected.

With the AC off, the sensor should return somewhere between 0.15 and 3V or so. With the AC running is will vary, but probably around 4V or so?
Yeah... I am definitely not getting that. Even when I forced the compressor on (jumped 12v supply to compressor) I was still .04-.06volts (40mV-60mV).

Everything points to the pressure switch being at fault... but this is the second new one we have installed...

This is the one I bought and is currently installed: https://amzn.to/2XkX1Eq prior to that the AC shop installed one they ordered and cost me $95...
 

Midwestdrifter

Engineer In Residence
Okay, with the sensor connected, cold engine, AC off, ambient temps around 75F.

BR/BL (ground) to RD/BL (5V supply) is 5.02V
BR/BL to BR/RD (signal) is 1.129V


4.5V is not good. So I see three possible issues.

Your ATC has a bad supply circuit.
The sensor is faulty, and is pulling the supply voltage down
The sensor is the wrong part (a web search says its correct).
There is some weird wiring fault (not likely, as you tested the wires).
 

alexk243

KulAdventure
Ran completely new, seperate wires from ATC to sensor with new harness. No difference...

4.5v at sensor supply when sensor is connected and sensor line shows .07v (70mV)



However I tried connecting the old sensor that I had lying around to the harness and the supply stayed at 5.18v and the sensor return was 4.98v... so it looks like the voltage to the sensor drops when it's under pressure and installed... Not sure what to make of that though. Midwest drifter you confirmed that the voltage should not drop when in use, right? If so I am lost...


There was 30ohms resistance in the ground while the circuit was in operation (brown/blue ground at ATC to ground at cigarette outlet. Is that problematic? If so why would the voltage be fine with the harness connected to the disconnected sensor?

 
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Midwestdrifter

Engineer In Residence
To reiterate, ohm measurements will not be accurate if there is current flowing through the circuit. It messes with the meters measurement current.

4.98V with the sensor at zero gauge pressure is not right? Higher voltage means higher pressure, and vice versa. Is it possible that the ground and 5 supply wires are reversed?

Lets get back to basics. What is the pin-out at the sensor? There are tiny numbers molded into the plug.

pin 1 should be BR/BL (ground)
Pin 2 should be BR/RD (sensor return)
Pin 3 should be RD/BL (5V supply).

This morning with the engine off, key on, I had about 1V between pins 1 and 2. After starting the engine and turning the AC on, this rose to about 2V. So the output voltage should rise with pressure.
 

alexk243

KulAdventure
Lets get back to basics. What is the pin-out at the sensor? There are tiny numbers molded into the plug.

pin 1 should be BR/BL (ground)
Pin 2 should be BR/RD (sensor return)
Pin 3 should be RD/BL (5V supply).

This morning with the engine off, key on, I had about 1V between pins 1 and 2. After starting the engine and turning the AC on, this rose to about 2V. So the output voltage should rise with pressure.
I'll check those pins when I get back home. What about pins on the back of the ATC? Which pins should those be plugged into?

Is this right?
19 - sensor feedback
6 - 5v supply
18 - sensor ground
 
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vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
Tough situation here.. what a nice guy mwd is! Reading through this I can’t help but ask if you’ve tried swapping in another, known to be good, ATC just to rule it out? Perhaps you did and I just didn’t see it. I’m gleaning that you’ve tested all the voltages and they seem to be good.... so frustrating!:bash:
 

alexk243

KulAdventure
Tough situation here.. what a nice guy mwd is! Reading through this I can’t help but ask if you’ve tried swapping in another, known to be good, ATC just to rule it out? Perhaps you did and I just didn’t see it. I’m gleaning that you’ve tested all the voltages and they seem to be good.... so frustrating!:bash:
I don't have another one accessible to me and not sure where I would get one cheap. The one I have in the was rebuilt last summer so was hoping that it wasn't the issue as most the voltage checked out... That is kinda what I am leaning towards now... ATC
 

vanski

'05 Snow Camper, '17 170 4x4, Adventure Vissionary
I don't have another one accessible to me and not sure where I would get one cheap. The one I have in the was rebuilt last summer so was hoping that it wasn't the issue as most the voltage checked out... That is kinda what I am leaning towards now... ATC
First, obviously mwd understands the details here at a very granular level so it might be worth getting his input. I’m just looking at this from 1k foot level. When you had it rebuilt last time did that fix any issues? I’m wondering if there’s a ground issue within the pressure sensor circuit within the ATC.

I have a T1N Sprinter getting ready for a build and it’s not being used... if you’d like I can pop the atc out (ac works on this Sprinter) and send to you for test. I’d need to charge you shipping and the cost of a new one but will refund the money (-shipping) once received back if it doesn’t fix your issue. If it does, you can just keep that one and then I’ll buy a new one. Perhaps there’s another supplier who will entertain working with you like this? Perhaps the company which supposedly fixed your ATC before? Feel free to PM me if you’d like me to send the test unit. Seems like you’ve exhausted the usefulness of your multimeter this go ;)
 

Midwestdrifter

Engineer In Residence
If the sensor gets 5v on the right pins, it must output a voltage that makes sense. With just 5v and ground connected, does the sensor work properly? How about your spare? If the etc can't supply 5v, it's probably the atc. If the atc's five volr supply chip is out of spec, you could always get a nether 5v supply from someplace else and use it externally.
 

alexk243

KulAdventure
If the sensor gets 5v on the right pins, it must output a voltage that makes sense. With just 5v and ground connected, does the sensor work properly? How about your spare? If the etc can't supply 5v, it's probably the atc. If the atc's five volr supply chip is out of spec, you could always get a nether 5v supply from someplace else and use it externally.
Haha funny you said that. I ordered a 5v transformer a few days ago to step down from 12-5v. Should be here today and hopefully that can rule out a sensor issue.

Ordered this one: https://amzn.to/2Gvu7L6

Will report back one I test the sensor with it.
 

alexk243

KulAdventure
It's fixed!!! Well kind of... Using the 5v transformer and supplying 5v and ground directly to the sensor and havening the output back to the ATC the AC functions correctly! So looks like the ATCs supply to the sensor fell under load and didn't provide enough supply to power the sensor. Which kinda explains that the rebuilder (eBay) probably bench tested it and it showed correct voltage, but they didn't test it under load.

I'll be sending the ATC back to them for a replacement (1 year warranty on their rebuild).

Sensor output (engine running, AC compressor on):


Output to AC compressor clutch:


Power supply from transformer under load:


And vent temperature:
 
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Midwestdrifter

Engineer In Residence
Cool, good find. For those who don't have a waranty, and are more mechanically inclined, there will be a 5V power supply chip on the ATCs circuit board. Follow the pin back to it. It is probably a 2$ part, and could be replaced if you are handy with a soldering iron. Another option is just wiring a standalone 5v supply for the sensor. Though you need to make sure there isn't a ground offset between the sensors ground and the ATCs ground.

Since you run fresh wires, the only other possible source other than the ATC, is a bad connection in the connector plug (female side). Thats not very likely, as that line only carries a few tenths of an amp at most.
 

sassmatt72

2006 high top long, Fully converted by me
Help me, PLEASE!

So I did the two larger pins on the relay (re-soldered) Only ones looked bad, but hard to tell,
do you typically need to re-solder all 6?

Now w key on (not running), fan switch in off position, I press ac dash button and blower fan runs ac LED lights up. start van AC compressor clutch doesn't engage, when I flip switch (added by previous owner) AC compressor clutch DOES engage, but doesn't get cold (at all)...
also front of rad electric fan doesn't run, but engine not too hot so maybe not supposed to come on yet???

Help, me, please to understand the diagnostic pathway. is my ACT 5v bad (hence AC compressor clutch extra switch)??? or ??? is this related to line pressure switch???

what does it mean that electric rad fan not on??? (is that just not hot enuf))).

As I understand it CAN communication is ok otherwise electric rad fan would default to on??? (is that right). ????

I'v read so many pages of posts I've lost my mind....

"help me O-biowin, your my only hope" lol@ me. thanks
 

Midwestdrifter

Engineer In Residence
IF the compressor is spinning, the AC should work. The top two vents will be cold, but if the heat is stuck on, the other vents may be hot if the engine is.

If there is a switch, they must have spliced somewhere. Are you sure the compressor clutch is connected to the ATC still? If the system pressure is low, the ATC won't engage the clutch. So use a scanner to read the ATCs reported pressure, or put a gauge set on the unit. It may have a low charge.
 
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Aqua Puttana

Poly - Thread Finder
First. What MWD posted.

...

So I did the two larger pins on the relay (re-soldered) Only ones looked bad, but hard to tell,
do you typically need to re-solder all 6?
One being bad doesn't mean all are bad, but reflowing all while in there is common practice. Did you inspect the relay contacts closely? They have some history of failure.

... Now w key on (not running), fan switch in off position, I press ac dash button and blower fan runs ac LED lights up. start van AC compressor clutch doesn't engage, when I flip switch (added by previous owner) AC compressor clutch DOES engage, but doesn't get cold (at all)...
As MWD said, check operating pressures. An added switch indicates previous problems so who knows what's really going on.

... also front of rad electric fan doesn't run, but engine not too hot so maybe not supposed to come on yet???
The Electric fan is enabled by engine temperature (over 221F?), high A/C compressor head pressure, or loss of CAN bus signal.

... Help, me, please to understand the diagnostic pathway. is my ACT [ATC] 5v bad (hence AC compressor clutch extra switch)??? or ??? is this related to line pressure switch???
:idunno: The clutch gets 12 volts, but you know that.

... what does it mean that electric rad fan not on??? (is that just not hot enuf))).
See above.

... As I understand it CAN communication is ok otherwise electric rad fan would default to on??? (is that right). ????
The electric fan running can be an indication of CAN bus issues, but the fact that it isn't running isn't verification that there are no CAN bus issues.

Some ATC info is here.
https://sprinter-source.com/forum/showthread.php?t=36931

:cheers: vic
 

sassmatt72

2006 high top long, Fully converted by me
Thx so much. I’ll dive back into it later. And I’ll let you all know what I find.
 

sassmatt72

2006 high top long, Fully converted by me
lol, put a set of gauges on it, nothing, pulled a vacuum -15 max, loud large leak from condenser behind hood latch area, loss of vacuum in seconds. condenser loose in mounts, parts time.
oooh
 

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