mchristyuk Posted March 31, 2022 Report Share Posted March 31, 2022 Hi Everyone, Been thoroughly enjoying my new (to me) Boxster the past few months, apart from the lack of aircon. The last couple of weeks I decided it was time I tackle it and having been round the entire loop of "usual culprits" I'm now at a crossroads and am scratching my head. I first of all was fully expecting the condensers to be more leaky than a net basket... however imagine my surprise when on getting the aircon re-gassed not only was there some old material in there, but it also passed a 25 minute compression test with no leakage. So the correct amount was put back in and fingers crossed the aircon would burst back in to life. Nope. So, next thing.. fuses.. all checked out OK. At that point I decided I had to get into the engine bay and check what was going on. The "Eureka" moment when I found the disconnected compressor lead turned out to be short lived.. as the clutch on the compressor still failed to engage. Putting a 9v battery on the compressor showed the clutch did work so for whatever reason power wasn't reaching the compressor clutch lead. In case it was a low pressure issue deactivating the compressor I bypassed the pressure switch.. nope.. still no joy. Took the relay out and tested that and it checked out every which way I could test it.. even swapped it for a "good" second hand spare.. still no aircon. The switch on the dash lights up when I press it.. and when the light isn't on I get the snowflake on the display.. so I'm guessing the switch there is ok. Out of desperation I started prodding around the relay 2 board with my multi meter to see if I could understand what on earth is going on. If I take the a/c relay out and directly wire the correct terminals then my compressor springs into life and I have lovely cold aircon.. so I at least know the system can work..! The relay switches when power is applied across two of its legs... and the sockets on the car have power for those two legs.. however when I plug the relay in it doesn't switch.. hmmm Checking closer I seem to only be getting 10v at the relay board for both relays (not sure what the other one is for..) rather than the 12v+ I was expecting. If I go to a different "ground" then I see 12v+.. but going back to ground on the board I only get 10v... but also when pressing the switch on the dash it never goes off.. stays at 10v. So I think there must be some kind of high resistance or dodgy grounding somewhere going to the relay board.. but also the dash switch is not appearing to switch the power to the relay either. I'm now stumped. Before I go full Basil Fawlty on the car... can anyone suggest anything I may have missed or have come across anything like this before?! Thank you!! Mark Quote Link to comment Share on other sites More sharing options...
Menoporsche Posted March 31, 2022 Report Share Posted March 31, 2022 “Temp control to Major Tom… check ignition and may God’s love be with you…” Quote Link to comment Share on other sites More sharing options...
½cwt Posted March 31, 2022 Report Share Posted March 31, 2022 Sound, if rather coded, advice from @Menoporsche, unless @Richard Hamilton has anything to add? Quote Link to comment Share on other sites More sharing options...
mchristyuk Posted April 1, 2022 Author Report Share Posted April 1, 2022 Perhaps a little too we’ll coded for this head! Im getting ignition grounding behind the dash controls vibes?? Thank you! Mark Quote Link to comment Share on other sites More sharing options...
mchristyuk Posted April 1, 2022 Author Report Share Posted April 1, 2022 Ok.. after some Googling the penny dropped I think... iginition switch to be checked... Looks easy enough to do, but currently snowing outside.. so will wait until the weather plays ball! Mark Quote Link to comment Share on other sites More sharing options...
Codfanglers Posted April 2, 2022 Report Share Posted April 2, 2022 I'm in the same boat regarding aircon that has never worked. There is still "some" gas in there but probably not enough to satisfy the pressure switch. The eco switch light goes on and off but nothing more happens. No lights on the tacho. I've had the cover off in case the compressor was seized and it turns freely, but didn't check the solenoid with a battery to pull in the clutch whilst in there. Would it do any harm to by-pass the pressure switch to see if the compressor clutch kicks in and if the system fires into life before getting it gassed up? Quote Link to comment Share on other sites More sharing options...
mchristyuk Posted April 3, 2022 Author Report Share Posted April 3, 2022 On 4/2/2022 at 9:51 AM, Codfanglers said: I'm in the same boat regarding aircon that has never worked. There is still "some" gas in there but probably not enough to satisfy the pressure switch. The eco switch light goes on and off but nothing more happens. No lights on the tacho. I've had the cover off in case the compressor was seized and it turns freely, but didn't check the solenoid with a battery to pull in the clutch whilst in there. Would it do any harm to by-pass the pressure switch to see if the compressor clutch kicks in and if the system fires into life before getting it gassed up? If you only run it briefly to check the clutch is working then no it won't hurt to bypass the switch. You'll only need it to run for a few seconds to know! Mark Quote Link to comment Share on other sites More sharing options...
mchristyuk Posted April 3, 2022 Author Report Share Posted April 3, 2022 Ok chaps... I got the ignition barrel out the dash to check the ignition switch.. and.. I don't think this is one of the "troublesome" ones which is easily or cheaply replaced? Looks light a later design and I guess everything is buried within that black case?? So.. with me still only having 10v at the Relay board it has to be a bad/broken earth somewhere between the dash and the Relay board, but not being up to speed with Boxster wiring I don't know what lives between the two? Could it be that the climate panel has gone a bit "dodgy" and although it's working internally the earth is broken coming out the back of it? I did have to replace the lower panel when I got the car to get the spoiler working at the back as that button was dead.... Cheers Mark Quote Link to comment Share on other sites More sharing options...
mchristyuk Posted April 4, 2022 Author Report Share Posted April 4, 2022 Ok so this morning I removed the HVAC control panel from the dash (car is now looking like a massive 3D jigsaw puzzle!)... and whether it is connected or not I'm still only seeing 10v at the relay board using the relay board grounding wires (note.. this is 10v with the car running.. only 8v with it off!). The culprit appears to be the green and white wire going to pin 95 of the relay. If I remove my multimeter from that and go to any other ground point on the car I get the full 12v. That green and white wire goes to something called the MFI+DI Control Unit according to this wiring diagram (Page 6): https://www.planet-9.com/d2/legacy/downloads/3366-987.1 WIRING DIAGRAMS.pdf It says it's on the rear left of the luggage compartment.. but all I've ever seen there is the relay support.. the green and white wire vanishes off through the rear bulkhead, unless they mean the rear left of the internal luggage area?! I'm not going to be beaten by this!..... Cheers Mark Quote Link to comment Share on other sites More sharing options...
½cwt Posted April 4, 2022 Report Share Posted April 4, 2022 Any advice @Richard Hamilton? Quote Link to comment Share on other sites More sharing options...
iborguk Posted April 4, 2022 Report Share Posted April 4, 2022 Love the persistence, good luck sorting. @Richard Hamilton any thoughts on this one - thanks ? Quote Link to comment Share on other sites More sharing options...
iborguk Posted April 4, 2022 Report Share Posted April 4, 2022 Love a cross-post 🤭 Quote Link to comment Share on other sites More sharing options...
Grizzlee Posted April 4, 2022 Report Share Posted April 4, 2022 20 hours ago, mchristyuk said: Ok chaps... I got the ignition barrel out the dash to check the ignition switch.. and.. I don't think this is one of the "troublesome" ones which is easily or cheaply replaced? Looks light a later design and I guess everything is buried within that black case?? So.. with me still only having 10v at the Relay board it has to be a bad/broken earth somewhere between the dash and the Relay board, but not being up to speed with Boxster wiring I don't know what lives between the two? Could it be that the climate panel has gone a bit "dodgy" and although it's working internally the earth is broken coming out the back of it? I did have to replace the lower panel when I got the car to get the spoiler working at the back as that button was dead.... Cheers Mark These things are easy to replace, but as you say are not cheap. I had mine replaced last year after it started acting up, well not starting to be more precise. They are not coded to the car, so are interchangable and the lock barrel is actually blank, you can put any key in it and it will turn, it works by reading the chip in the key head. I think they are like this from 987 onwards. Quote Link to comment Share on other sites More sharing options...
Paul P Posted April 4, 2022 Report Share Posted April 4, 2022 Might be talking borrox here - so take it with a sense if internet "commentary" On the diagram you linked I think I see the wire you are talking about ... you say pin 95 on the relay - I read that as 85 - and I don't think that's the pin number, (I read the PIN as 2) - I think the 85 is the "terminal number" (See https://en.wikipedia.org/wiki/DIN_72552 ) often things like permanent power (T30), switched power (T15). 85 says coil -ve Perhaps check on what you are seeing on the other end of the coil ( the term 86) one - to the board without the relay in place - does that go between 12v and 0 on with the switch ( or does it go between open and closed circuit to "switch the coil") Also - re "left of passenger compartment" - often resources are lhd specific, so I always look "right" as well as left, and I am pretty sure the cars DME/ECU is behind the carpet in the boot on the engine bulkhead. Suspect I am adding more confusion than helping - but I dont get why that connection stays at 10v irrespective of the switch. Whereabouts in the country are you - there maybe someone nearby with some diag kit - if the car is throwing a code then it may help find the root cause. Quote Link to comment Share on other sites More sharing options...
Richard Hamilton Posted April 4, 2022 Report Share Posted April 4, 2022 The green and white wire does connect the relay to the DME (the engine ECU) which is behind the carpet lining on the front wall of the rear compartment. It goes via a black 30-pin connector, so it might be worth unplugging that, and give it a spray of contact cleaner. Quote Link to comment Share on other sites More sharing options...
mchristyuk Posted April 4, 2022 Author Report Share Posted April 4, 2022 Thank you everybody for your pointers... here's what I've managed to come up with so far.. 1) I'm an idiot (ish).. @Paul P you are quite right about the terminal numbers and they're actual reason for existence.. so it wasn't that I was getting 10v at the 85/86 terminals.. I was getting 12v at 86 (yay) and 4v at 85 (boo).. of course the differential gives me by 8v without the engine running. Turning the switch on or off on the dash doesn't change 85 from 4v (boo). 2) @Richard Hamilton tearing the carpet off lead me to the DME unit and the green/white wire connector which is supplying the rather suspect 4v to my relays.. alas cleaning the connectors and putting them on and off did not fix anything. So.. does this start to appear like a goosed DME unit if it's only ever putting 4v out along the relay switching wires?? Many Thanks Mark Quote Link to comment Share on other sites More sharing options...
Paul P Posted April 5, 2022 Report Share Posted April 5, 2022 More guess work..... Reading some (not directly 987 but some reference to panemeras) suggesting that the ECU turns "off" the a/c compressor rather that turns it on (i.e. default run state is ON) don't know but it's possible that to turn it off it raises the voltage on the -ve side of the coil enough to prevent the relay from closing - so is it possible that this is expected behaviour because in it's mind the ECU think the AC needs to be off. ? If you are getting 12v to one side of the coil (86) then surely you would want "0" ( ground) the other side to make it work - if you put 12v to both sides then the coil won't fire. I still reckon that a session on a diags system with Porsche smarts might tell you something about what the various modules, sensors and switches are seeing and would help to narrow things down - perhaps the ECU is refusing to activate the compressor because it thinks ( or maybe there is) an issue in the system. Quote Link to comment Share on other sites More sharing options...
mchristyuk Posted April 5, 2022 Author Report Share Posted April 5, 2022 5 hours ago, Paul P said: More guess work..... Reading some (not directly 987 but some reference to panemeras) suggesting that the ECU turns "off" the a/c compressor rather that turns it on (i.e. default run state is ON) don't know but it's possible that to turn it off it raises the voltage on the -ve side of the coil enough to prevent the relay from closing - so is it possible that this is expected behaviour because in it's mind the ECU think the AC needs to be off. ? If you are getting 12v to one side of the coil (86) then surely you would want "0" ( ground) the other side to make it work - if you put 12v to both sides then the coil won't fire. I still reckon that a session on a diags system with Porsche smarts might tell you something about what the various modules, sensors and switches are seeing and would help to narrow things down - perhaps the ECU is refusing to activate the compressor because it thinks ( or maybe there is) an issue in the system. @Paul P I believe you are quite right that the ECU tells the system to go OFF if anything doesn’t look right OR if the button the dash is lit ON. As the +ve side goes pretty much straight to 12v via a fuse the switching only occurs on the -ve side. I imagine the ECU sends the 4v to “break” the ground and therefore turn the relay OFF. So chances are that for whatever reason the ECU is not happy to activate the AC even though it’s gassed and the low pressure sensor is ok. There must be some other input that’s triggering things. I’ve got a bit of kit coming tomorrow that should be able to get into the DME and the AC ECU to tell me more about what’s going on. Will report back when I know! Mark Quote Link to comment Share on other sites More sharing options...
Paul P Posted April 5, 2022 Report Share Posted April 5, 2022 18 minutes ago, mchristyuk said: @Paul P I believe you are quite right that the ECU tells the system to go OFF if anything doesn’t look right OR if the button the dash is lit ON. As the +ve side goes pretty much straight to 12v via a fuse the switching only occurs on the -ve side. I imagine the ECU sends the 4v to “break” the ground and therefore turn the relay OFF. So chances are that for whatever reason the ECU is not happy to activate the AC even though it’s gassed and the low pressure sensor is ok. There must be some other input that’s triggering things. I’ve got a bit of kit coming tomorrow that should be able to get into the DME and the AC ECU to tell me more about what’s going on. Will report back when I know! Mark Cool - one possibility is the cabin temp sensor ( in the HVAC control unit) giving odd readings - and the car thinking that its out of range of the A/C - have seen that affect the heated seat operations, cabin temp sensor reading between -40 and +50 C in a few seconds. There's a cheesy little fan that draws air over the sensor - seems like a likely candidate for getting gummed up/"burnt out" That threw a diags code that was picked up on PIWIS. Look forward to hearing next instalment.... Quote Link to comment Share on other sites More sharing options...
iborguk Posted April 5, 2022 Report Share Posted April 5, 2022 1 hour ago, Paul P said: Cool - one possibility is the cabin temp sensor ( in the HVAC control unit) giving odd readings - and the car thinking that its out of range of the A/C - have seen that affect the heated seat operations, cabin temp sensor reading between -40 and +50 C in a few seconds. There's a cheesy little fan that draws air over the sensor - seems like a likely candidate for getting gummed up/"burnt out" That threw a diags code that was picked up on PIWIS. Look forward to hearing next instalment.... He's referring to my old 987.1 there. The fan was gummed up with 15 years of dust and carp (sic) which I cleaned out, worth a bit of housekeeping anyway even if nothing to do with this. Quote Link to comment Share on other sites More sharing options...
mchristyuk Posted April 5, 2022 Author Report Share Posted April 5, 2022 8 minutes ago, iborguk said: He's referring to my old 987.1 there. The fan was gummed up with 15 years of dust and carp (sic) which I cleaned out, worth a bit of housekeeping anyway even if nothing to do with this. When I had the HVAC unit out the dash I could see the little fan it was spinning quite happily and didn't look too awful in there... Lets see what horror stories the tools unearth tomorrow! Mark Quote Link to comment Share on other sites More sharing options...
mchristyuk Posted April 6, 2022 Author Report Share Posted April 6, 2022 Ok Gents, Here is todays developments! My iCarSoft reader turned up and I (after some mucking about) convinced it to connect to the cars system and clear all the legacy errors. I then get just 3 errors reoccurring C131,C141 (and another I forgot to take a picture of... to do with the electric roof.. but that works.. so..). It appears these errors are not un-common and could be related to not having the original stereo in the car. The more interesting ones are to do with the readings coming out the AC ECU. Intake temperature -40 Outlet temperature -30 Refrigerant Pressure 0 Clearly a pressure of 0 would stop the aircon from working.. however if I disconnect the pressure switch this goes to 3bar which should be enough to get the AC working (certainly the front fans then kick in).. but alas it does not. What puzzles me is normally you would "short" the pressure switch to trick it into a reading.. how come disconnecting it has achieved that?!.. that would mean a sensor failure would have the AC on all the time which surely can't be right?! Also the garage doing the refrigerant top up had it on a pressure leak down test for 25 minutes AND the system wasn't empty anyway when it was charged.. so I'm struggling to believe it has emptied it's guts in the time it took me to find the disconnected compressor... Finally I don't know if the Intake temp and Outlet temps actually matter.. I don't have climate control just the manual system so it wouldn't need to know either of these to balance the temperatures. So chances are my car just doesn't have those sensors? I know adding the climate control HVAC unit, whilst plug and play, won't give you climate unless you have extra temperature sensors added... Hmmm....! Mark Quote Link to comment Share on other sites More sharing options...
mchristyuk Posted April 7, 2022 Author Report Share Posted April 7, 2022 Gents.. Day (who knows what) on Marks AirCon mission... Digging around I'm pretty confident that the intake/outlet temps are correct as the car simply doesn't have the sensors as it's manual air con and not climatic. People who have retro fitted the climatic head unit have found it doesn't do the climate control bit as it's not getting any signals from interior temperature sensors.... So.. Last night I decided to buy a pressure gauge for the aircon to get a real readout of what's in there rather than just rely on the computer readings, but as I'm impatient to get this sorted I decided I'd just try the "pen tip on the schrader valve" test to see if anything is in the system... and.. nope.. not a sausage. So.. Despite the car passing the aircon regas testing without a single leak (allegedly..) it now appears to have dumped all it's contents somewhere. My hunch at the moment is that when I reconnected the compressor that either a) as soon as it spun up it leaked or b) the resulting high pressure on the other side of the compressor caused a leak. So.. I've got a UV light on the way for which I'm going to start digging around the assorted pipework and compressor and see if I can find the culprit. I will not be beaten, and it's a great learning experience to find out more about your own car.. I find you tend to bond more with them once you've scraped a few knuckles and swapped blood for oil! 🤣 Mark 2 Quote Link to comment Share on other sites More sharing options...
½cwt Posted April 7, 2022 Report Share Posted April 7, 2022 Keep chipping away at it, the answer is in there somewhere! Took me ages to trace back why I had no interior or vanity lights. With help form the forum I found the problem in the alarm control module under the passenger seat of all places. Yes, for those that know it had got wet in the past but this seemed to be the only lasting damage. Quote Link to comment Share on other sites More sharing options...
Richard Hamilton Posted April 7, 2022 Report Share Posted April 7, 2022 One of my pet hates is people fitting an aftermarket stereo and not getting the factory unit coded out of the system. The times I've had trying to diagnose faults for people and had to spend half an hour re-coding before I can start..... Quote Link to comment Share on other sites More sharing options...
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