Heater not working (possible my fault but need you'r confirmation)

Post Tue Oct 20, 2020 4:04 pm

Hey guys,

Ever since i removed the dash and did a lot of wiring work for the heater/AC system, the heater never worked. As it is getting colder, i am trying to investigate the issue, however it MAYBE caused by crossing (accidentally) some wires.

First thing, i checked Fuse 20, it is working and so is the blower speed control.

Unplugged the heater valve connector, checked for voltage with ignition on. Reads battery voltage regardless of heater temperature position (from full cold to full hot) always ready battery voltage.

That should not be the case correct? it should ready 0v when fully cold and after 20 degrees of moving the controller to hot it should read battery voltage? I did indeed do some soldering work on that long wire from the temp control panel to the inline fuse and back to the valve connector. Sadly it is all wrapped in tesa tape so i can not see the solder, as well as limited space.

With the heater valve connector disconnected, started the car, when i place my fingers on the lower metal pipe (under the heater valve) it got hot, really hot but NO hot air. The pipe at the top, after the heater valve (towards the heater exchange/matrix) is warm, but nowhere near as hot as the lower hose.

With the heater valve connector plugged, that same warm pipe got warmer (top pipe), but not close to the lower pipe (that was really hot).

I suspect two issues, first i crossed some wires and the heater valve is constantly getting 12v from the temp. control unit.
Secondly, i suspect i may have crossed the coolant hoses in the engine bay.

Does this sound correct to you guys?

Post Tue Oct 20, 2020 10:52 pm

I'm not clear if the heater fan is working properly on all speeds?
You appear to be correct that somehow you've managed to apply permanent power to the heater valve. Either just unplug the connector from the valve or pull the fuse out as a temporary fix.
The heater hose that comes from the rear of the cylinder head must go to the lower stub pipe on the bulkhead, and it's important to make sure there's not an airlock in the hose connected to the top stub.

Post Wed Oct 21, 2020 7:57 am

Brianmoooore wrote: ↑
Tue Oct 20, 2020 10:52 pm
I'm not clear if the heater fan is working properly on all speeds?
You appear to be correct that somehow you've managed to apply permanent power to the heater valve. Either just unplug the connector from the valve or pull the fuse out as a temporary fix.
The heater hose that comes from the rear of the cylinder head must go to the lower stub pipe on the bulkhead, and it's important to make sure there's not an airlock in the hose connected to the top stub.

Yes Brian, the fan is working in all 4 speeds.
Okay, i need to re-trace some wiring to correct the permanent power to the heater valve.
I shall also check the hoses, make sure that they are connected correctly.

Post Sat Oct 24, 2020 9:12 pm

I may have found the issue, after spending nearly 1 hour removing all the tesa tape, i found one 0.5mm brown wire (a ground) not connected to anything. Tracing it back to the temperature control unit. Basically the heater valve just got constant voltage and the control unit was not grounded in order to control it.

Doing everything from under the dash is painful work, traced all the wires, all look good, hopefully tomorrow i should finish up a couple of things under the dash and test.

Post Sat Oct 24, 2020 10:25 pm

Temperature control unit?? Does this car have climate control?

Post Sun Oct 25, 2020 9:55 am

Brianmoooore wrote: ↑
Sat Oct 24, 2020 10:25 pm
Temperature control unit?? Does this car have climate control?

Yes, it has the automatic temperature control option, an electronic motor replaces the cable running behind the temp. knob to the flaps.

Post Sun Oct 25, 2020 1:05 pm

That would have been something of relevance to mention in the OP. This is one of the rarest E30 options out there and I've never set eyes on one.
However, I do know that the valve is used to modulate the heater temperature output on these, so your disconnected earth might well be relevant.

Post Sun Oct 25, 2020 9:09 pm

Brianmoooore wrote: ↑
Sun Oct 25, 2020 1:05 pm
That would have been something of relevance to mention in the OP. This is one of the rarest E30 options out there and I've never set eyes on one.
However, I do know that the valve is used to modulate the heater temperature output on these, so your disconnected earth might well be relevant.

Actually, i thought so as well, being a rare option, but it turned out to be a very "demanded" option for colder EU countries.

I managed to find a "guru" on these systems in the German forums, he was kind enough to send me an electrical plan and how to test both the control unit and the motorised temperature flap. He is like you, unsure if the valve value/voltage is "regulated" or just switched on or off and the mixing flap motor is used to control how much of the heat is used or not.

I am pulling things apart, i am not happy with the wiring behind there. Will check the valve, the control unit and the mixing motor first independently. If they are all responding as they should, then i have a faulty wiring somewhere.

PS: A lot of E30 owners on the German forums adding AC to their non standard AC equipped E30s are looking for that auto temp. option, found numerous threads on people converting to this system, apparently it is something sought after locally in Germany at least.

Post Sun Oct 25, 2020 11:48 pm

My car started life in Germany and it has climate control. No idea if it works though.

Post Mon Oct 26, 2020 7:07 pm

Took the dash off in 40 minutes, 20 minutes later the heater box came off.

I traced every single wire, and followed the German electrical plan i was sent (link below). I tested the heater valve (it clicked) and the motor for the mixing flap (it responded), so the issue was either the wiring or (more expensively) the control unit.

Apparently there was one 0.5mm green/brown wire incorrectly spliced, again heading towards the temp control unit (it gives 12v).

I was following the US electrical plan, which is very similar except for that one extra wire. Basically there is a 2.5mm green/brown wire that splices into seven smaller wires. Three for the AC/Recirculation button, one for the blow speed, one for the temp. control unit, one for the heater control module (the 3 sliders that direct airflow, mine is electrical) and one for the heater valve (inline fuse).

I was very nervous hooking things back up and starting the car, at first no heat, 5 mins later still no heat. I kind of gave up hope, till the workshop owner came along and started squeezing every hose he can reach, then heat started coming out of the vents. Sadly the car was sitting on a declined surface, so it took a while to bleed the air out of the system. But everything works, from full fresh air, to full heat and everything in between. I need to attach the small trim pieces, since it was late but problem solved.

Here is a link to the wiring diagram for E30s with this option, note you may have one wire coloured differently to the mixing flap motor, BMW did some change and did not update their plans to my knowledge.

http://www.huemmer.info/m3/slp/M3-SLP-Klima-89.pdf

Post Mon Oct 26, 2020 7:15 pm

Do we have any wiki gurus left?

It would be good to put that diagram on there somewhere.

Ben

Post Tue Oct 27, 2020 10:10 pm

Beyond my powers to add it to the wiki, but I've downloaded and printed it off for my own files. May be of use some day on here.
The circuit diagram confirms that the water valve is controlled directly by the ECU, and not by a simple on/off switch, but gives no indication of the nature of the control signal.

Post Wed Oct 28, 2020 7:01 am

Brianmoooore wrote: ↑
Tue Oct 27, 2020 10:10 pm
Beyond my powers to add it to the wiki, but I've downloaded and printed it off for my own files. May be of use some day on here.
The circuit diagram confirms that the water valve is controlled directly by the ECU, and not by a simple on/off switch, but gives no indication of the nature of the control signal.

According to the gentleman who sent me the diagram, that workshop manual does not have any certain testing procedures for this system. The only exception(s) are to make sure that the heater valve responds directly to voltage (on/off) and the mixing flap motor responds to power. If the wiring is correct and if the inline 2 amp fuse is not faulty, the manual states "the ECU is faulty and should be replaced". The US electrical AC/Heater plan has a whole list of testing procedures for the heating and the climate control/AC system.

No mention, as you stated, the nature of the control signal.