Heater control valve -- substituting an E39 unit

[bouliac]

Dear Friends,
I took my winter car, an 1992 E34 Touring, out of storage last week as seriously cold weather has arrived in Montreal. The heater control valve is stuck, and while I was able to get it to function using the most highly sophisticated tools and techniques, involving a big dumb hammer, I realize that I should have replaced it 5 years ago, when the Bosch OEM units were still available, instead of going through the well documented DIY repair procedure which I did at the time. I don't want to open it up again, I don't want to pay BMW for a branded unit that is over 500 US dollars (-- about $720 here), the Bosch OEM units are gone and deceased, unless of course the molds have been repurposed for the $60 units, which I don't want to use either. Previous posts have mentioned that the E39 HCV can be used with "slight modifications", and I would like to go that route because it is available, and even the BMW branded units are relatively affordable. Looking at pictures of the E39 HCV I don't see how the ports can line up to be fitted to the E34. So if anyone has actually made this work, I would very much appreciate hearing from you !

John in Montreal

1992 E34 M50 Touring, 5 spd swap.
E30 1992 E30 M40 (Euro) cabriolet
E9 1973 3.0 coupe

[shogun]

Moved from 5 general to E34 forum

[demetk]

Looking at pictures of the E39 HCV I don't see how the ports can line up to be fitted to the E34.

Anything can be made to fit with some creative use of extra hose and fittings. When mine fails I'll plug in a cheap single zone e46 valve.

[south42]

I have some good used ones for the e34.


Andy

[JThomp33]

You could always buy a donor and 'refurbish' your existing one:

https://www.bimmerforums.com/forum/s...internals-Info

Not too difficult and I've had no problems the last 3+ years.

[moroza]

I'd be less worried about hose routing than about control compatibility. E34 valves use pulse-width modulation to selectively close the valves in pulses. What does E39 use?

Deep on my back burner is a project to replace the heater control with mechanical valves controlled by cables, or possibly a pair of E30 valves. Both would/could delete the IHKR control module, and require modification of the control panel - the former with generic rotary cable controls, the latter with E30 potentiometers.

[bouliac]

Thank you for your help. Andy, I may call upon you, and I appreciate your offer. However, I've already delved into the innards of the present valve. It was in surprisingly good shape, especially the seals, so I polished up the pistons with fine steel wool and put it back into service and for three years it has given me hot and cold, but no gradation in between. Whiich is okay, but let me remind folks that I live in Quebec, and a squirrely HCV is not an occasional nuisance, it is a big deal when the average temp is below freezing 2 1/2 months a year. I'm not a fan of the IHKR, and the previous generation of valve on my E28 worked much better. Still in former threads, a member of the forum engaged in a little debate with Shogun : Shogun said to bite the bullet and buy a new one from BMW but one member, whose name I don't recall, said that the E39 unit was the same with a slightly different configuration of hoses, a different electrical connector, at less than half the cost. In point of fact, the seal and piston kits sold on ebay are the same for both E34 and E39. I'm a firm believer in fixin' stuff, but hydraulics tend to have very fine tolerances, and in the present case I would like to buy a new unit.

[moroza]

What hydraulics?

How rapidly does the temperature change if the controls are switched between full cold and hot? If the transition is slow, I suggest your valves are sticking. If the transition is rapid but in-between settings give only one or the other, then the valves are fine and the control panel or module is defective.

[bouliac]

Hydraulics in the general sense that the HCV is a piston valve regulating the flow of a pressurised liquid. Good idea about the IHKR, I will verify the voltage at the connector from the control panel to the HCV. Can anyone suggest what readings I should look for ?

[moroza]

I suppose you could call it hydraulics, but pressure as such isn't important here, the pressures involved are nowhere near most hydraulic systems, and the tolerances aren't as fine either. The system has more in common with garden hoses and household plumbing than hydraulics. Not sure what the voltage should be, but one way to find out is to set the heat to full cold - in which condition, the valves should be getting a constant voltage (technically, a full-width pulse) to keep them closed - and measure at the plug. You'd need an oscilloscope to check the right PWM pattern. A quick-n-dirty substitute is to listen to the valves opening and closing - colder settings mean longer On pulses and shorter Off periods.

A clogged or defective cabin air temperature sensor (inside the control panel) could cause wrong signals to be sent to the valves, even if everything else is working correctly. There's a small fan drawing air across the sensor, which over time gets clogged with dust.

[bouliac]

Maroza, a quick look at some forums indicate that the E39 valve is controlled by PWM as well.

[ross1]

Quit overthinking this and get a proper replacement valve. You'll have a rats nest of hoses and wires plus the E39 doesn't mount to the E34 bracket.
Andy has offered good used ones, I also have one I'd sell and no doubt plenty on Ebay too.
Aftermarket units are available for around $50. If the solenoids and hose nipples are good these aren't hard to repair either.

[bouliac]

I doubt that I'm smart enough to overthink anything, but I take your point. I'm going to check the signal from the control panel as per Moroza, and I'll report back.

[fo3]

Yeah, as above I agree with Ross.

Also:

You could always buy a donor and 'refurbish' your existing one:

https://www.bimmerforums.com/forum/s...internals-Info

Not too difficult and I've had no problems the last 3+ years.

You say your heater is stuck and not working. The heater valves default to always 'on' in these cars. The HVAC controls give a ground to the coils to turn the heater off every time you start the car and don't want heating. So no current or valve movement you should have heat, ie the fail position electrically is always to heat.

So if it's not heating then it's a simple task of taking them apart and cleaning them because they are probably dirty and frozen in place. It's not going to be an electrical problem if heaters don't turn on, just dirt.

[moroza]

If it can do full hot and full cold, it's not fully stuck (but may be sticking).

[ross1]

I doubt that I'm smart enough to overthink anything, but I take your point. I'm going to check the signal from the control panel as per Moroza, and I'll report back.

May I use that one?

[bouliac]

Thanks Ross, its. yours for free !

[fo3]

If it can do full hot and full cold, it's not fully stuck (but may be sticking).

Yeah true. Considering they got it functioning by whacking it before I say it's a sticking problem.

Here's the circuit:
heater valve.PNG

Always 12v to the valves, the IHKR switches heating off by activating the solenoids by providing ground. Fail position is always heating, unless stuck.
If they are clean and not sticking (when a ground supplied they turn heating off, when no ground they cleanly turn heating on without sticking) , then I'd be checking all the thermistors that the IHKR uses to control temp (left and right).

E: but usually if something electrical has gone wrong it will be one side affected first. For both sides to not work I'd guess filthy cooling system and sticking valves.

[bouliac]

I have 11.9 v. (car not running) between ground pin and and pins at the connector when the driver's and passenger's rotary heat control is off. So the circuit s are connected although they thermistors may be faulting in between full on and full off). I put a stethoscope on top of the HCV and ran a long rubber tube to the ear piece so that could hear the valves while actuating the heater controls from the driver's seat. One valve clicks with a delay while the other is quiet as a dormouse. The diagnosis is thus that one of the HCV valves is sticking and the other is stuck, so the the HCV needs to be rebuilt or replaced, and once that is done, I can see what can be down about the gradation of temperature. If that is still a problem I'll look at the IHKR. Finally, I conclude that the best solution, aided by the fact that no-one listening has actually installed an E39 HCV in a E34, to go with a used E34 unit. Thank you all for your help because, baby, it's cold outside !