AC Wiring Issue

This is not a TDI car, but a 1.8T.
I have been checking out the wiring on my daughter's car for two weeks now. I tried a none good 384 relay and another pressure switch.

My two questions are about VCDS measuring block 61. I have two fields AC Readiness and AC Compressor. The Readiness is showing A/C Low and the help says it can only be A/C Low and A/C High. Does anyone ever see anything else? The Compressor of course says off. (Note: The compressor is good as I jumpered the clutch and it turns on. The fans work as supposed to. It something with the 384 commanding the AC)

Second Question: My 384 relays don't match the wiring book. I am supposed to have a pin 75 and a pin 4. The relay has HLS and 15. My assumption is 15 is actually 4, and HLS is actually 75. Does Pin 4 or 15 just turns on the light in center console. Also is 31 just the ground?

Because I have voltage on pins 30 and HLS/75, I assume that 87A is just not commanding the 384 to turn on.

Oh, I forgot. I have 75 psi ambient pressure and I jumpered pins 1 and 2 on the pressure sensor and the AC clutch wouldn't come on. As mentioned earlier, If I injected 12vdc into the clutch wire behind the headlight and it engaged.

NO it never comes on, but I do get an intermittent temp sensor code. That may just be it.
I will check it out and see.

I think you got it. The Temp Sensor G62 stays at -48 C even though the dash temp changes. I will be changing the theromostat housing anyway and already have a new sensor. Hopefully this will fix it.
Thanks.

While running scans the G62 came up to 90C. All codes cleared but AC still won't come on.

Only the GLX or W8 Passats have Climatronic, and therefor they are the only ones that have any OBD via the DLC.

All the AWM (1.8t), BHW (TDI) and non-GLX ATQ (V6) cars use the same HVAC system, with no OBD or data of any kind.

There is a J28 diode in the circuit to the compressor power feed somewhere. I have heard of that failing, not really sure where it is though. It is after the F38 ambient temp switch, which is what prohibits compressor operation when temps are below a certain level.

Do you have a good diagram of the system? It is not overly complex.

The Engine controller does have the ability to turn off the compressor under high load, high RPM, overheat, low idle, etc. conditions. This is done via a signal to the J314 A/C retarder relay.

oilhammer said:

Only the GLX or W8 Passats have Climatronic, and therefor they are the only ones that have any OBD via the DLC.

All the AWM (1.8t), BHW (TDI) and non-GLX ATQ (V6) cars use the same HVAC system, with no OBD or data of any kind.

There is a J28 diode in the circuit to the compressor power feed somewhere. I have heard of that failing, not really sure where it is though. It is after the F38 ambient temp switch, which is what prohibits compressor operation when temps are below a certain level.

Do you have a good diagram of the system? It is not overly complex.

The Engine controller does have the ability to turn off the compressor under high load, high RPM, overheat, low idle, etc. conditions. This is done via a signal to the J314 A/C retarder relay.

Click to expand...

OilHammer,
Thanks. Yes I have the big blue book with the diagrams. I have been looking for the diode but no luck yet. Everything ohms out right and I get what seem to be correct voltages. I just can't find out why the 384 relay isn't turning the compressor on. I do believe it's the signal you are referencing to the 384 relay but I can't figure out why it would be doing that.
I have jumpered the pressure sensor, injected 12vdc to the output of the pressure sensor (no help), injected 12vdc at the green connector behind the headlights (works)...just can't figure out the 384 relay.

I changed the G62 and it still won't work.

There should be somewhere in the engine data the A/C request signal.

If I remember I will drive my AWM Passat to work tomorrow and poke around on it and see what I can find for you to check. Its A/C works fine, and it likely will not be cold enough yet to prohibit compressor engagement.

Dumb question, but are you certain the retardation relay 384 is in the correct socket? Reason I ask is I think there are some empty (unused) sockets on some cars that the 384 will plug into.

I can also verify that on my car for you too.

oilhammer said:

Dumb question, but are you certain the retardation relay 384 is in the correct socket? Reason I ask is I think there are some empty (unused) sockets on some cars that the 384 will plug into

Click to expand...

Yeah. It's in the right socket and I took it from the crashed car that was working just fine. This is the replacement car (exact year). She said, it saved my life before...I want another one.

Both 384s do the same thing. THanks for helping me out. I am an electronic technician and can't figure this stupid thing out.

OK on my car I have Measuring Group 050 showing compressor status, Block 4 is compressor command. Does your car show this, and what does it say when you press the A/C button?

-48c means a broken open circuit to the temp sender
If I recall that temp sender is a duel output type
One output for gauge and the other for ECM !

Oil Hammer, I recall that this says something like Not On or something. I will check it this weekend.

Peiphil, I changed the temp sender when I changed the leaking housing. It still doesn't work. I eventually got a reading with the old sensor and the new one also reads temps.

Oil Hammer,
MB050, field 3 has AC Low and field 4 has compr Off.

The Fan turns on and the AC light on the panel lights up but the compressor does not turn on.

So the ECU is not commanding the compressor on? The 4th Block remains OFF even when you switch the A/C button on and the engine is running?

Could the trinary switch on the rec/drier be bad or the wiring to it?

oilhammer said:

So the ECU is not commanding the compressor on? The 4th Block remains OFF even when you switch the A/C button on and the engine is running?

Click to expand...

Correct. I could try the ECU from the wrecked car.

thundershorts said:

Could the trinary switch on the rec/drier be bad or the wiring to it?

Click to expand...

I tried the pressure switch on the R/D. I checked out the wiring to it.

is it a 4 wire switch? the low pressure contacts should be closed and the high ones open. if the high pressure contacts close it cuts compressor current

thundershorts said:

is it a 4 wire switch? the low pressure contacts should be closed and the high ones open. if the high pressure contacts close it cuts compressor current

Click to expand...

I don't remember the pins, but we looked it up and jumpered the high side pins. I also changed the switch with one from the wrecked car.

high side switch part of trinery should be open, if closed it may indicate circuit is shorted to ground, preventing compressor from coming on. You could if all else fails, run a wire to compressor with an on off switch.

We jumpered a wire from the green connector behind the headlight and it works from there. It now too cold to do much but I will check out the wiring again soon and try changing the ECU.
Thanks.

This thread was helpful, it lead me to check all my sensor connections and I hadn't plugged everything in ....nope im a dummy lol

I've had trouble from mice chewing on the ambient temp sensor wire that is located between the ECU box and the interior wall Try checking there.