Ac control panel ac button problem

[Legacy7770]

Hello everyone decided to gas up the ac on my focus after changing the compressor which kept blowing the fuse. 

Replaced compressor no more fuse blowing. Great hooked up my Manifold gauges scale etc. Start to fill the system Clutch spinning but not compressing!!!!

Hummmmm ac switch lights up great 

Right time to break out the launch then live data. Brought up the pid for the ac switch 

Press the button live data shows on then goes straight to off. If you hold the button down the compressor runs and data displays on. Do you think this points to a switch problem?? Can I change the switch??

Any special way to fill the ac system on the 1.0 ecoboost??

Yours sincerely Steve Evans 

[Legacy7770]

Anyone else heard of this before guys???

[Tdci-Peter]

On 2/10/2018 at 1:31 PM, Legacy7770 said:

Replaced compressor no more fuse blowing. Great hooked up my Manifold gauges scale etc. Start to fill the system Clutch spinning but not compressing!!!!

You don't say if you evacuated the system before filling.

Assuming the air has all been removed, then as it responds to the switch, I would guess either the evaporator temperature sensor or the a/c pressure sensor is sending the wrong signal out. If these are ok, then next suspect is the heater control head. For manual A/C, the connection from heater head to BCM is marked "A/C on" on the wiring drawing, which implies the signal is energised all the time the a/c should be on. But the control is drawn as a push button, so it looks like the heater head converts presses on the button to turning the "A/C on" signal off and on. So there could be a fault in there.

For climate a/c (DEATC), the DEATC head is connected to the MS CAN bus, so can send the a/c control signals to the ECM (which controls the compressor) over the CAN busses.

If by any chance it has not been evacuated, then some air will have got in during the compressor swap. The a/c circuit should contain refrigerant and oil only, no air and absolutely no water vapour! Any appreciable air in the system will greatly alter the High/Low pressures as soon as it starts, and may cause the system to stop as soon as you release the button.

 

[Legacy7770]

Thanks Peter yes it was evacuated for 30 minutes mate. When I connect up the scanner and pull up some live data of the ac button it shows off even if the light on the button is on. When you press the button and hold it shows on the scan tool And stays on. The pressure switch is in the back of the compressor and three wire but this was changed with the compressor. 

Any more information peter will be great 

Thanks Steve 

[Tdci-Peter]

2 hours ago, Legacy7770 said:

When you press the button and hold it shows on the scan tool And stays on. The pressure switch is in the back of the compressor and three wire but this was changed with the compressor. 

I can only go by the wiring diagram for this car, and this may not be 100% correct due to the number of variants. I am also assuming it is manual a/c, not climate.

The two sensors directly controlling the a/c are: the pressure sensor, 3 wires to the ECM, almost certainly it is a transducer with a linear output, so I would expect there to be a PID for this. Also an evaporator temperature sensor, 2 wires to the BCM. I would expect to see a PID for this also, and it would cut out the a/c if it read too low.

The illumination of the a/c button seems to be decided inside the heater control head, a small electronics pcb mounted behind the heater control panel presumably. There seems to be no feedback signal of actual a/c operation state to the heater control head. The only signal shown is an output from the heater control head to the BCM, marked "A/C on".

As with all things on these cars, hidden software plays a major part. Switch and Temp sensor go to the BCM, and the ECM can read these signals over the CAN busses. It is the ECM that makes the final decision, it has the wiring for the clutch control & the pressure sensor, and it also knows the state of the engine (rpm, temperature etc) in case that is needed.

I have included pics of the heater head connections and connector below, see if they are anything like what is on your car. (No idea why some of the text on the connector view is double typed, it is like that on the pdf!)

[Legacy7770]

Thanks Peter it' manual ac. The car completes a KOEO self test  cluch engagees fans run etc with  no codes. So I'm thinking the only thing I can see whats wrong is the switch issue. Spoke to someone in ford and was told there is common problem with the wiring harness at the back of the control panel. I need to know what voltage I need to see on the pressure switch etc. So the search goes on!!

Thanks again for all your help mate much appreciated Steve 

 

[Tdci-Peter]

2 hours ago, Legacy7770 said:

common problem with the wiring harness at the back of the control panel

The pics I posted were of the control panel (heater control head) wiring & connector. It does sound increasingly like a fault with that little pcb or its wiring.

The pressure sensor is wired direct to the ECM, not to the heater control panel. It will almost certainly have 5v, Ground and a signal pin. Signal is probably 0-5v or 0.5 to 4.5v, for the measured pressure range.

[Legacy7770]

Thanks Peter mate you're a star much appreciated I've got a day off wensday then I'll pull out the heater control panel but I think we are on the right track. 

Thanks again for all the help peter much appreciated Thanks Steve 

[Legacy7770]

Hello everyone found some time to get back onto the focus. Got the ac ice cold compressor working pressure on the Manifold gauges correct etc. 

Then shut the car off left to do a different job came back tried the ac again and it didn't work!!!!!

OK dear pulled the codes and found the code B10B8 ( push buttons)

Status-97 (component or system operation obstructed or blocked)

Any help would be much appreciated guys 

Yours sincerely Steve Evans 

 

[Tdci-Peter]

On 2/13/2018 at 4:56 PM, Legacy7770 said:

OK dear pulled the codes and found the code B10B8 ( push buttons)

You first thought it was the switch.

I came round to the idea that it could well be the switch.

Someone in Ford thought it was probably the switch.

Now the car says it is the switch.

Well, that pretty much proves it can not possibly be the switch. Bound to be something else!

Googling B10B8 suggests you may be the first person in the world to manage to extract that code from a Focus! Lots of hits for Lincoln & Mercury, but Focus, no.

Getting back to being a bit more sensible: That it ran for a while suggests the sensors are ok, and an intermittent contact in that switch circuit has to be the most likely suspect. That B code probably came from the BCM, which is where the switch signal goes. Some diagnostic systems, like Forscan, tell you which module the DTC was found in. The status data could be trying to tell you the signal is stuck on when the BCM expects it to be off, or vice versa.

(By switch, I think I would include the pcb, connectors & wiring that carry the switch signal to the BCM.)

[Legacy7770]

I'll let you know tomorrow peter when my second hand unit gets to me. 

Thanks for the quick reply and great information mate you're a star much appreciated Steve 

 

[Legacy7770]

Well decided to break out the launch. Jumped in to the powertrain control module. Pressure sensor reading and Manifold gauges are the same. No ac request being sent from the powertrain control module to the ac cluch. 

So I'm left with the heater control panel or wiring problem. As I mentioned in a previous post pushed the button and bingo ice cold ac. OK great job done turn engine off quick cup of tea start the car then tried the ac again didn't work. 

Hummmmmmmmmmmm 

Thanks again Peter Steve 

[Legacy7770]

All done now peter it was the heater control panel thanks for all the help mate much appreciated Thanks Steve