Mike’s Retrofit Aircon Cruise Heated Seats ++

The switch/sensor will be in the high pressure feed into the condensor. Likely directly on the receiver-drier. Might be a 4 pin switch. 2 pins for the low pressure cut out - cut the clutch if the system has a leak - and 2 pins to the fan relay to switch on the fan when theres pressure. No point in switching on the fan if theres no pressure at that point in the system.
 
So look for the drier. Likely down behind a headlight. Look for a switch/connector on top of it.

I dont have aircon so dont know exactly. But that's where I'd be looking.
 
TiggR_R1 said:
If it's any help to you.
on my 2.8 (March 1999) with aircon from factory, when I start the engine from cold and switch on the air con from the dashboard switch
my fan (currently semi seized) does kick straight in......... some times needs a nudge to get it going ;)

I hope that helps rather than adds to any confusion.
Click to expand...
Thank you: that is what I expect it should do. Annoyingly mine does not!

Could I ask a favour?
I have spent literally the last 6 days chasing my Aircon slow speed fan issue - everything works EXCEPT, my low speed fan does not come on with the cabin switch. After hours of Chat GPT searching/logic and testing, everything appears to be as it should, except it still does not kick in!

Could you look at the BMW part number on the high speed relay and photograph the schematic on its side. It is the third from the rear of the car in the nearest row to the offside in the main fuse box inside the engine bay. It’s easily removed with a pair of pliers lifting vertically.
March 1999 cars were a hybrid crossover rare car so it would be useful to know the exact relay used in a car that is the same period and has working slow speed Aircon fan.
Many thanks in advance
 
Hi MickeyG.

I hope this helps.
 

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Sorry, no: But you photo is very useful by colour code! it’s the purple one directly below your finger.
My guess it ends 911? That is the Fast fan relay.
Could you look at the two Yellow ones on the right of the Purple one - Hopefully the schematics show an internal diode in the earth on the extreme right relay - not sure about the central yellow one?
 
I'll try again MickyG.

See if these pics help, also the comment from Althulas about the radiator temp sensor plug there is a bit of information online about some Z3's for whatever reason having the plugs wired differently mine most definitely has the brown wire on the central pin.
 

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TiggR_R1 - Thank you very much for these photos they are very useful: they have not solved my problem 😂, but put me in a much better position to solve it.
I had naively transferred the relays from my facelift donor to my prefacelift Z3 expecting them to work 🥴.
I have now inserted relays matching your description/photos, and which now correspond to the BMW schematic diagrams for a late 1998 yo March 1999 Z3.
Electrical circuits are not my strong point, though I can follow it in principle and run basic voltage and continuity tests.
Althulas’s comment regarding the incorrect wiring is something I had read and was able to set aside as my plug is the same as you show (photo again useful).
So, now all the pointers are to either the Aircon controller or wires leading to and from it.
Now that zi know I have the correct relays in place my testing becomes meaningful.
(Previously with the wrong relays it was a case of “Rubbish in: Rubbish out!”)

ChstGPT has been very useful as a logic calculator and advisor on what, and how to check the next process.

The search continues……..
But thank you both once again for your help.
 
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It's a shame that has not fixed the issue MickyG,
If I can be of any further help with pictures etc, fire away!
If I'm awake no problem to take a look/photo.
I work night shift through the week so my responses may be a little sporadic but happy to help if I can.

I don't know if this helps or if it is accurate 1999 BMW Z3 fuse box diagram - StartMyCar
 
Althulas said:
Mike might this possibly apply to you with the green and brown wires on the fan being wired incorrectly from the factory?

https://www.reddit.com/r/bmwz3/comments/1j1318o
View: https://www.reddit.com/r/bmwz3/comments/1j1318o/tracking_down_ac_issue/
Click to expand...
Hi Althulas - Thank you for your research: I had seen this - apparently it was due to a translation error (German design - American built!).
Google keeps telling me to look a the fan resistor which is the most common failure in Z3s.
I have a new two stage fan which I have tested working through their respective relays when the earth pins are jumped. I believe the resistor appeared in early Z3s which had a single winding and used a resistor to slow it down.
 
The plot gets thicker……..

Reconfiguring my relays to match those shown in TriggR_R1’s photos I now have a different set of outcomes!

Nothing works!!! 😳😂😤

The compressor does not come on now in sympathy with the slow fan that does not start.
This is not necessarily a bad thing as testing has shown they both work when an earth is jumped to their respective relays.
This now has a consistent logic, pointing significantly to the condenser controller or DME (ECU), as they both have transistors that, given the correct inputs, should switch to earth to trigger the relays.
I have been able to test my system all the way back to both these components, and everything seems to be as it should, however I am in no position to test them. So finally I have admitted defeat snd booked it in for a diagnostic test at LRS
Obviously the controller is the much cheaper part so I am hoping it is the culprit, and not the DME (ECU).
 
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Mike.....when you say 'controller', do you mean the a/c and recirc fan switch in the cabin?
 
Pond said:
Mike.....when you say 'controller', do you mean the a/c and recirc fan switch in the cabin?
Click to expand...
Hi Andy
The condenser control module straps onto the side of the HVAC unit: I have tried my spare cabin switch, but it makes no difference.
Hopefully I’ll find out tomorrow exactly what the problem is🤷🏻
 
Do you have the signal wire from the engine ECU?

On a 1998 E36 318ti (manual controls and an AC button) it's:

Terminal 36, black/blue to T5 compressor relay.
T69, violet/grey to T9 on the AC switch.
T11 black/grey to black/brown to T4 on pressure switch.
T68 grey/violet to black/green to T3 on double temp switch.
T57 red white black/grey to T5 on normal speed relay.

LOW SPEED RELAY:

Four terminals.

6 is green/red linked to T5 on high speed relay.
5 is black/grey from engine ECU.
4 is green/violet to fuse 16 - also for compressor relay T4, high speed relay T8.
2 is black/blue to T2 on fan motor

HIGH SPEED RELAY:

Five terminals:

2 is blue, to T3 on fan motor.
5 is green/red to low speed relay.
6 is red/green to fuse 48.
8 is green/violet to fuse 16.
4 is black/grey to pressure switch T2.

Pressure switch (four terminals), T2 is for 15 bar, T3 is for above 18 bar.
 
Andy
Thank you for this detail - I’m not sure that it will apply to my “changling” Z3 - it was literally the last month run out of production before the facelift was built and so circuits are not as they were in full analogue direct wired cars.
My Z3 certainly has some control logic passing through the ECU/DME, Instrument cluster and the Condenser controller.

I took it to LRS for diagnostics this morning: the outcome was double edged……… the basic hardware that I have installed along with the Z3’s in-built circuitry seems to all check out: it physically works very well - the technician could force the compressor and fan on, but could not get the cabin switch signal (which he could see) to then initiate an ECU output and apply continuous control. As he said “There is nothing wrong: except something is wrong!”

Yet more research this afternoon has suggested the“ car” has to be programmed to recognise that there is an A/C System (The ECU clearly has the logic to control it) it simply needs to be able to see that there is an Aircon system to be controlled.

So, my physical efforts have been totally successful , but I have more research to do to complete the retrofit. I now need to find someone who knows how to programme an ECU and sync it with my binnacle and condenser module………. I think I’ve been here before………does anyone know a BMW auto technician well versed in programming ECUs?
 
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TiggR_R1 said:
It's a shame that has not fixed the issue MickyG,
If I can be of any further help with pictures etc, fire away!
If I'm awake no problem to take a look/photo.
I work night shift through the week so my responses may be a little sporadic but happy to help if I can.

I don't know if this helps or if it is accurate 1999 BMW Z3 fuse box diagram - StartMyCar
Click to expand...
TiggR_R1 (or anyone with an 09/1998 - 03/1999 2.8)
Do you have a multimeter?
I’ve been using ChatGPT AI - its logic is unbelievably quick and lucid, though its “facts” are sometimes questionable or even contradictory, so has to be treated with caution.
Nonetheless it has suggested trying to check, and thereby confirm, circuit logic against your car as it is from an identical manufacturing period ( a crucial point given Z3s underwent considerable wiring changes around this period).

Simply testing relay terminal inputs and outputs would provide significant clues to my circuitry’s validity.
 
HI MickyG.
Yes I have a multi meter.
What do you need checking?
 
Hi
As my issue seems to be getting the slow speed fan to kick in, logic suggests checking your base pin voltages going into the slow speed fan relay so that I have a known working circuitry to compare against my inputs.
Can you remove your slow speed fan relay and check the voltages on all 5 pins in the base with
Ignition off
Ignition on
Then with
Aircon on
This should/will show that your relay receives a change to kick your fan into action.

I have a suspicion that my pins 85 and 86 in the base are the wrong way around and the relay is designed to only work with current flowing in one direction.
Many thanks for all your help - it may again not solve my problem, but each time it reduces the possible options and focuses where the ultimate issue must be.
Mike
 
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