OBD details

[GeoffWW]

Hello,
Whilst regularly looking at othe owner’s problems, I now have one of my own.
I read on a BMW website yesterday, of a hidden link to the cooling controls which overrides the dash board controls.
A couple of days ago, I accessed my 75’s OBD for the water temperature direct reading, via the trip button, pressed to 19, then the ‘Off’ to 7. The temperature only got up to 72 very slowly, but the air coming through into the car was stone cold, and the air con was not on, and whatever settings I tried.
With the 75 having more or less the same electronics as BMWs, does it also have this hidden link. It looked like my shower control in miniature, with a ring of coloured segments, going from strong red, fading into faint blue then intensifying to deep blue.
During my first attempts into the OBD, I went past the first 1-19 group of numbers and found myself watching all the gauge needles going through their full cycles, and I may have caught something during this time which has knocked out all heat from the engine, even though the pipes are warm.
I have read on the forum of the heater matrix becoming blocked and need flushing out, but this sudden stop of heat at the same time of accessing the OBD, makes me suspect my fumbling on the OBD have caused this sudden change.
I am sure that some years ago, a list of the various OBD support functions was somewhere on the Forum.
Can any forum member direct me to this information so that, if our cars do have this hidden switch/ system, I can access it and restore heat, albeit minimal, to my car.
I am going to order a new thermostat from DMGRS, once I have finished here.
TIA for any help
Geoff.

[Arctic]

Hi Geoff.
This may help below from T-cut

https://the75andztclub.co.uk/forum/s...ad.php?t=55585

Trebor (Rob) Nano crew.

[SD1too]

Hi Geoff,

What you activated wasn't OBD; On Board Diagnostics. That's the system which is accessed by code readers via the multi-pin socket under the steering wheel. You were using the built-in instrument pack diagnostics and it is impossible for that to have any effect upon your heater output.

Your heater matrix may well be performing inefficiently. I suspect that this may be due to limescale formation due to using tap water when preparing antifreeze solution.

The coolant temperature slowly reaching a maximum of 72˚ suggests a thermostat fault which is very common with the diesel. This would have a significant effect upon the heater so should be addressed as a priority.

Simon

[GeoffWW]

Hello again, thanks for your replies,
Replying to Arctic, thanks for your video of accessing the water temperature. I went out this afternoon for a 6 mile run and then idling on my drive afterwards. The temperature went up to 72 degrees and stayed at this temp for the 10 minutes, idling on my drive.
I kept the engine idling, trying all variations of the heater controls, but the air coming into the cabin was still stone cold, even with the water pipe going into the heater was very hot. That is why I mentioned the BMW system with their hidden temperature controller, and wondered whether our’s have a similar feature, hidden , but that I may have upset the setting on my early fumbling on the OBD to get the water temperature.
I have ordered a replacement stat from DMGRS, the front “in-line” one and will fit it later this week, I already have one of their front hose stats, which has been in the car for about 4 years.
Whilst I have drained the coolant to swap the stat, I will try to flush through the heater matrix with water. At present, I don’t know where the return hose is located, somewhere under the battery, I think?
Replying to Simon, I think you have got your two diagnostic systems mixed up. The socket under the steering wheel is for errors codes, whilst the trip reset button on the speedo is for the actual running performances of the various things accessible, through it, fuel consumption, water temperature, distance travelled over various periods, etc.
Whilst waiting for the stat to arrive, I will give my FBH a check over. I had removed it, thinking that the FBH water circulation pump was causing the problem, but the impeller was free.
I had another reply in my Pm’s from Lincoln which gave me access to the full list of the OBD parameters covered. But there is still no mention of the hidden BMW temperature controller.
I will report back once I have the new stat and done the flushing.
Thanks to all,
Geoff

[alan richard]

Just to add to this . . .

I have experienced only twice (not fiddling with diagnostics, just driving) a complete loss of heat output from the blowers even though the temperature setting was cranked right up.
Every other time the behaviour is normal with plenty of heat coming out, so (probably) not a water issue.

I was going to ask here about the internal temperature sensor for the ATC but it hasn't done it again since.

-A

[GeoffWW]

Hello Alan,
Thank you for your input. I received the stat yesterday afternoon and will be installing it today.
Whilst waiting for its arrival, I have been searching through loads of information in Rave, a Car Mechanics run on various maintenance jobs, and on “YouTube” for information about the heater matrix, but could not find any clear information as to the piping arrangement on the matrix. If they both enter it at the same point, is there an internal piping arrangement to give the water flow right across the matrix, rather than ‘ in and out at almost the same point’?
Back to you, Arctic, if I may.
You have done many different jobs on our cars. Can you throw any light on the water flow accross the matrix. Does the water flow go diagonally across the matrix, bottom to top/one side to the other? Any thoughts you have will be appreciated.
Thanks again,
Geoff

[Arctic]

Originally Posted by GeoffWW

Hello Alan,
Thank you for your input. I received the stat yesterday afternoon and will be installing it today.
Whilst waiting for its arrival, I have been searching through loads of information in Rave, a Car Mechanics run on various maintenance jobs, and on “YouTube” for information about the heater matrix, but could not find any clear information as to the piping arrangement on the matrix. If they both enter it at the same point, is there an internal piping arrangement to give the water flow right across the matrix, rather than ‘ in and out at almost the same point’?
Back to you,

Hi Geoff.
Have you read this below. Post 72 but maybe best to read it all.

https://www.the75andztclub.co.uk/for...=100619&page=8

https://www.the75andztclub.co.uk/for...d.php?t=288291

[GeoffWW]

Hello again, Arctic.
Thank you for your links to the other Forum members with heating problems. I have read through them and agree with one of the entries who had taken the matrix out, flushed it, and then thought the water circulation was going straight in and out.
This morning, I removed almost everything, engine cover and air duct, the battery and the box it was in, loosened the under bonnet fuel filter, air filter cover, and then started to try and get the filter hosing base, but then saw it was not possible without disturbing the ‘Top of the engine’,
I followed the, what I think is the feed, from the front of the engine, across to the FBH, current removed, and then on around the battery box to the bulkhead. Below this pipe, I could see the return to the engine pipe, coming out of the bulkhead, and then doubling back along the front of the front plenum too ????. On accessing your information, I saw a drawing of the water circuit with my lost end going across the rear to rejoin the engine, on the back, offside corner of the engine. Could it be joining the engine again via the original thermostat?
After seeing the above, I put every thing back, and then set about replacing the front in-line stat with the new one delivered yesterday from DMGRS.
I decided to take off the inlet manifold to give me better access to the jubilee clips holding the old one in place. It took me ages, over half an hour, just to remove the old stat. To stop the coolant getting spilt everywhere, I made a collector out of a 2 litre pop bottle placed under the clips with an extended ‘tongue’ to go right under the connection.
So having got the new stat in place, and replacing the manifold, and air ducting, I started the engine, idling and having set the OBD to 19/7, watched the engine and the OBD rise up, through the 50’s, 60’s, past the old stat’s 72, on to 80, and finally up to 86degs.
I then carefully started to release the radiator cap, only to have to tighten it with coolant filling up the ‘gutter’ around the top of the expansion tank. After sponging up the spilt coolant, I went for a drive, for a couple of miles to see if I could get the temp higher than 86. I got it generally to 87, but for a very short time, hit 88, the temp stamped on the stat bulb.
After this, I raised the expansion tank as high as the connected hoses would allow, on wooden blocks, then rev’d the engine, up, and I also raised the FBH bleed as high as I could, and the coolant was there straight away.
Having put everything back and packed up my tools, I left the car, locked and went inside, opened up my link to the Forum, and saw your last entry with the links.
Regarding the ‘Heater Bypass Control’, I have my handbook where it refers to this control on page 41. That is the only place I can find any reference to it. I am convinced that this ‘control’ in my car has become detached from whatever it is supposed to be linked to, in the bypass position. Looking at the Rave drawing of the ‘Temperature and Distribution control’ on page 82-20 in the AirConditioning, Description and Operation, there is a side view of the heater unit, showing all the flaps, the heater matrix, and the evaporator, with arrows showing the varuios flow directions.
There is one flap, pivoted in the centre of the drawing, which in the ‘down’ position, stops all the air flow to the heater matrix, and sends it straight up to the front face level outlets. I believe this is where my problem lies. How is the dash control linked to the flap? There is no indication at all in Rave, or here on the forum.
Which side of the heater has the link to the flap in question. How does one get at the back of the dash . Would it be best through the radio aperture, or from a side.
I have gone on long enough. Any comments or suggestions would be very welcome.
Thanks again for h your help Arctic, I will go and read on
Geoff.
P.S. Sorry it’s so long.

[SD1too]

Originally Posted by GeoffWW

There is one flap, pivoted in the centre of the drawing, which in the ‘down’ position, stops all the air flow to the heater matrix, ... How is the dash control linked to the flap?

That's the air blending flap Geoff which controls the temperature inside the car. It is driven by a servo motor.

Originally Posted by GeoffWW

Which side of the heater has the link to the flap in question.

Both; there is a servo motor and flap for both passenger and driver's sides (see the ATC ECU connector C0791 pins 1 & 2 and 11 & 12 on page 82-23 of RAVE).

Simon

Edit:

Originally Posted by GeoffWW

Regarding the ‘Heater Bypass Control’ ... Looking at the Rave drawing of the ‘Temperature and Distribution control’ on page 82-20 in the AirConditioning, Description and Operation ...

The heater by-pass outlet is labelled no. 11 in this drawing. Just below it is the flap manually controlled by the thumb wheel on the car's fascia, situated below the clock. As you can see, this blends fresh or chilled air with the heated air delivered through the face level vents (labelled no. 1). Consequently if this thumb wheel is rotated fully to close the flap, heated air should remain at the face level vents.

[GeoffWW]

Hello SD1too,
Thank you for your entry. and your pointers into Rave. I took the radio unit out this morning and saw the cable connecting the thumbwheel to the lever on the side is in place and secure at both ends and works without any play.
That leaves it to the connection between the lever and the flap being broken or loose.
I had to go out this morning and I set the OBD to read the water temp, which went straight up to 87deg C.
It looks like I need to get access to the offside of the heater unit to see if the lever is loose or broken. At the end of my trip, the centre of the dashboard felt as though the chill had been remove, by the hot matrix inside.
I will let you know how I get on.
Geoff