That's great information, guys. Thanks. I shall investigate. It runs when the a/c is blowing cold air.
Thanks for the info, it's a little different on my car but I'm not sure if it's the difference of comparing LHD and RHD. Mine appears to be exactly as the previous diagram shows, but something is clearly wrong, so I'll poke around a little more.
Ben, are you sure it's different? Image Unavailable, Please Login I think the above schematic should be coloured as follows (schematic for the LHD cars): Image Unavailable, Please Login In which case the valve is after the heater core.
The hot water valve is "after" the heater core (which is the first item to receive the hot water from the engine) in both diagrams (but red would've been better rather than green).
Thanks for the replies. I thought my set up was correct per the diagram, but it's hard to tell and surely it has to be wrong. I shall dig around further.
Hey all. I just spent some more time upside down in the footwell and it is exactly as per Urs' description: 'hot water hose from the engine comes out the sill, goes directly into the heater core, then exits it and gets regulated through the heater valve on the way out the firewall towards the return circuit of the engine coolant'. Does anything look off to you guys? Image Unavailable, Please Login I can confirm that this line temp sensor is not part of any of my problems. I have removed it and jumpered the two wires, as others have done as I prefer the idea of that. Thanks for the tip everyone. Unfortunately though, I still have the two faults listed in my first post.
Have you tried clamping the heater hose off completely and see what happens for fault1? Have you tried a brand new AC relay for fault 2?
I remember the days i could get into the footwell, just wishful thinking these days as my knees creak
Have you measured the voltage at the hot water valve wires when it is plugged in and should be working with key "on" and AC "off"? There is nothing else in the AC system that can cause "When I turn the a/c on, it dumps out load of piping hot air" except the hot water valve not being closed when it should be.
When you sit in the car with the ignition on (fan low/off, no engine running so you can hear things), AC or AE or Defroster button pressed and you turn the temperature knob all the way to cold, you must hear the compressor clutch engage. When you turn the temperature knob all the way to hot, you must hear the compressor clutch disengage and the heater valve close. And vice versa; easy test. Do you hear that?
Thanks for the replies, everyone. Apologies to you all for my tedious postings. The hoses going into and out of the heater valve are hot. Intersting test. There seems to be all the correct noises. When I turn the temp knob to warm, I can really hear the valve open and the water flowing. When I turn it back cold that noise stops. Okay, after rigging up some testing apparatus, the voltage is 11.25, which is pretty darn close to 12v. Is this very slight drop in voltage enough to give me the problem I'm having? Image Unavailable, Please Login
Unfortunately, no. 11.25V should be plenty to close the hot water valve. But the hoses should remain "cold" when/if the hot water valve is truly closed. Don't know if it is possible to mess this up in this way, but have you actually followed the hose connected to the bottom nipple of the hot water valve to see where it physically goes?
I shouldn't have had you focus on the hose at the upper nipple of the hot water valve as that will probably always be properly connected to one side of the heater core. This figure describes better how things might get "swapped" incorrectly: Image Unavailable, Please Login Make sure the hose connected to the bottom nipple of the hot water valve goes to the radiator tube in the front bonnet.
Thanks for the reply and diagram, Steve. Yes, I just checked again, the bottom hose from the hot water valve goes through the bulkhead and toward the radiator. Spoke with a friend at the weekend and he reckons it could be a faulty part, even though it's brand new (and pricy). Presumably I can pull the part (huge pain) and test it on the bench? Something 'does' happen though when I twiddle the temp knob. So maybe it works, but just not well. silverlam's first post is to apparently mock me. I guess I have a ferrarichat bully. Image Unavailable, Please Login
Certainly -- 1st level test would be to apply 12V and blow into the upper nipple (giggity ) -- it should be blocked (and, likewise, with no voltage applied you should be able to blow thru it). In my case, I had to extend each hose out into a bucket and start the engine to determine which was the hot supply hose. Not something that you'll need to do, but you might need to do something like temporarily splice in a clear section of hose so you can visually confirm/deny coolant flow when "off" and with heat "on" -- just a thought...
It is possible the new valve has a crappy chinese made internal plunger, the only ones that I believee are still manufacured, with a weak spring and or a leaking rubber seal. You can definitely bench test as this post notes. You can also easily dismantle it and check the plunger conditon and seal directly when apart. On other ideas, have you checked the temp sensors that the computer reads in order to actuate the heater valve? There are certain resistence readings, I believe the work shop manual has the data and you can measure at the wiring connector pins near the compter under the passenger footwell. Also, are you sure the relays are not defective? Did you replace the original italmec relay with a modern one without rewiring the connector for the different relay pin layout? You could also hook up ac pressure guages and see what happens when the ac runs, and then stops running, eg. Is there a pressure spike causing the ac to shut down. Are you sure your condensor fan is running when the ac is on? It really seems to me like the ac is shutting down to protect itself by overheating, and then works again after things cool down?
... just test the heater valve first ... there is no way you have hot air entering the car if that valve is closing properly. Unplug the valve and hook up 12V and a ground directly to it and start your car. If you have hot air from the heater your valve is bad. If you don't get any hot air the valve is good - your control system is the issue.
Thanks for the reply, moysiuan When I first encountered this always hot phenomenon, I replaced the hot water valve with a brand new one assuming that was the problem and that's the end of that. It's possible both the old one and new one are broken. I have not done this. I swapped them with known working ones that are exactly the same. Yes, the condenser fan is definitely running and I removed that temp switch so it always runs when the a/c is on, as some have recommended. The a/c gauges read within range (shown in pic in first post), then the compressor stops running and the pressures go way up.
Try bench testing your old heater valve with a 12 volt source, and you can see the plunger move up and down (or not). The solenoid can fail but more typically it is the internal rubber plunger seal that cracks and leaks. Will give you the idea of what the valve in the car is doing. Where did you get the new heater valve, they were not commonly available, perhaps they are now but reproductions may not be made to the old standard. Crazy possibility given all the work done on the system, but is there enough (or too much) refridgerant in the system?
A place that specializes in BMW parts. A BMW E28 collector buddy of mine recommended them and it was the best price I could find. 'Maximillian Importing Company' and it cost $355.00 total. Really weird sounding gentlemen on the phone.
Yes, I have heard about the BMW part cross reference. I recall someone saying the hose connections were smaller, when you compare with your OEM item, were the hose connections in fact the same size? It will be good for others to know a new valve is available.
The same heater valve is used in the 456 and other F models. I replaced mine with a 2nd unit from a 456. I think you should just clamp off the heater hose initially and if the AC works fine and is cool then you'll know
