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Thread: Defrost but no floor heat

  1. #1
    Join Date
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    Isetta, 735i, 280sl

    Defrost but no floor heat

    Can anyone direct me to a thread that might help a new bee get his HVAC fixed.... it only blows defrost...where would you start?

    The vacuum pump fires right up and pressurizes the system then turns off as it should, but the dash buttons are not doing anything...but defrosting! (US 85' 735i)

    It all worked last week....but the car has been sitting for some time so wondering if the new usage has blown diaphragms or something ....the lines in the engine room are all in good and supple to the fire wall...

    Seems like this would be a good topic for a DIY paper since everyone has these problems...

    I would be willing to write it up as a comprehensive document with part numbers, steps and sources if I can get some direction to start tackling it...

  2. #2
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    Hook up the vacuum gauge to the firewall

    Sent from my LGLS755 using Tapatalk

  3. #3
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    Thumbs up

    You need to start by searching this forum and my user name. We have discussed the HVAC system AD NAUSEAM and I have posted enough information for your eyes to bleed and to 100% repair the system. Buy a Mityvac. Buy a few brass 1/8" T adapters. Buy about 10' of 1/8" silicone hose. Start there and get vacuum solid from the plenum to the firewall, then to the reservoir, and into the cabin. From there look for my pictures posted and test ALL EIGHT pods, some are dual tit. Doing a few is half assed and will create more issues.

    Just be ready to replace the cowl ones, defrost, and center vents at the very least. Front feet is a lot of fun...

    Do you drive on 30 year old tires? No, the rubber degrades. Same with the diaphragms in the pods.



    Disconnect the pump before it roaches itself as you obviously have issues with the system.
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    11/1984 735i (10:1-265/6)
    Ford, MB, and GM round out the pack.



  4. #4
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    Thanks...I found the treasure trove!

    For the Mityvac is the MV8000 the unit that you would recommend?

    After digging into the cowl area, would the next place to disassemble be the hvac control and radio area?

    Dreamed about owning an E23, and finally I do - hoping I'm not in over my head with complicated systems ...Ive worked on plenty of cars, but your in a different league -- this stuff is a little more involved than basic mechanical repairs that I have done - ugh...

    Thanks for making yourself available...

  5. #5
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    Thumbs up

    That one looks good, I have an old ass SIlverline.

    Pull center console first. Drop knee bolster, corner piece by glove box, and glovebox. Slide rear part all the way back, I mean all the way. And pull remainder up and out. DO NOT FORCE anything. It will come out. Then you have access to the HVAC solenoids...these too need to be tested.

    Only reason to pull radio/HVAC stuff is to access center pod, orange and yellow hoses I think. Chances are you need to do it. Cut old pod away, use M4x12mm bolt to install new. New are pink and black, old are green and black. Front feet is not fun to access, AT ALL, it is the dark blue hose. You can test it off the Mityvac, I recommend at the pod directly for all.

    Defrost and recycle by accelerator. Recycle is a MFer to do, patience is key. Do same trick with cutting dead pod out. Fifth pod is behind heater core panel, a MB W124 pod can be used to fix for cheap. Black hose here. This usually works. Other three under hood.

    Like I said, what HVAC works on any 30 year old car let alone BMW? Start with the air flow working, then heat if it leaks, AC really is not hard just needs some good tools and new parts.

    No clue what it will boost value, dollar wise on the car, but driver's satisfaction goes through the roof! I have windows up in summer in a black on black 745.
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    11/1984 735i (10:1-265/6)
    Ford, MB, and GM round out the pack.



  6. #6
    Join Date
    Aug 2011
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    Metairie, LA, USA
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    Quote Originally Posted by Kazoo View Post
    Thanks...I found the treasure trove!

    For the Mityvac is the MV8000 the unit that you would recommend?

    After digging into the cowl area, would the next place to disassemble be the hvac control and radio area?

    Dreamed about owning an E23, and finally I do - hoping I'm not in over my head with complicated systems ...Ive worked on plenty of cars, but your in a different league -- this stuff is a little more involved than basic mechanical repairs that I have done - ugh...

    Thanks for making yourself available...
    It’s a job for sure and opens a whole new discussion of “while you’re in there....”. I started with dash replacement, then since it was off do the pods. Then that turned into climate wheel, then checked out the heater core and thankfully it must have been changed along the way. Was fortunate and caught the doors that open and close to direct air to the desired places were about to fall off and got that fixed. (Could also be a problem for you). Evaporator, dash bulbs, Speedo board batteries, .... you can get a lot done while you’re at it. Just be up for it because to get the dash out, if you go that route, a lot comes out with it.

    Anyway as Eric (HitmanX) says; it’s time and doing it will go a long way to sorting problems and getting the car back like you want it.








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  7. #7
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    This is getting scary :-| haha

    I'll tackle the easier points and see how I do, if I start getting in over my head.....I think I might be better to start with other priority items on the repair list first - that may not be as involved. Not driving her in the New England winter anyways ...so I can live without heat! Mostly wanting to make her all "right" again.

    IN the meantime my fuel gauge is pinned past full as is the temp gauge.... Be better to be able to watch engine temp than keep the feet warm!

    Was going to do a cooling system flush and replace the temp sensor at the same time and hope for the best...

    Maybe pull the fuel sender from the top of the tank and see if I can test that for proper operation...

  8. #8
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    Thumbs up

    I have changed all pods with the box in, not a problem. OLD WIVES TALES that the dash needs to be removed. Same with replacing heater core. All bullshit people have heard and preached from folks with no hands on experience. Armchair mechanics.



    Better replace all the hoses, chances are many are original from West Germany. Do the 130mm water pump pulley (get a 13x1040 belt too) and 'A' stat housing. Lower temp aux fan switch. S38 fan blade if stock three row radiator, B35 fan with clutch if on two row.
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    11/1984 735i (10:1-265/6)
    Ford, MB, and GM round out the pack.



  9. #9
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    Agree with Eric. I was intending to change the dash so I got into the "while you're in there" loop and just dug into everything since the patient was open and am glad I did. Or I should say Tim because he was the one that did it all. Anyway, whichever way you go don't get intimidated. It's pretty straight forward, and there's a lot of help here.

  10. #10
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    I did heater core and pods with the dash in. It is a good knuckle busting test of patience.

  11. #11
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    Thumbs up

    Ah, the ol' 'while I am in here' trap. Just dealt with that on a 7.3 Diesel I bought after Harvey.
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    11/1984 735i (10:1-265/6)
    Ford, MB, and GM round out the pack.



  12. #12
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    Call me crazy... but could my pods be ok! (Sounds like a women going in for a breast exam!!)

    Messed around with it today and found something interesting!! When you select the a/c function and then use other controls like selecting the rear Hvac button, you hear the pods activate, flaps open and then you feel the air distribution go right to the back seat... the same with the re- circulating function...you hear all the flaps move.

    But when you select either of the heat buttons nothing but defrost works - and selecting other options like the rear hvac button also do absolutely nothing - dead quite when on the heat functions.

    The other interesting note is that the blower volume wheel does not do anything until you spin the wheel to full blower... with any selections - heat or a/c. No variable air volume selections available....

    Also, When you select a button with the a/c on, you hear the pods activate, the flaps move -- then the vacume pump comes on for a few moments to re-perssureize the system, then it clicks right off... not what you would expect if there were leaks...???

    Could it be the assembly with the blower wheel is bad or something other than pods ?

  13. #13
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    Thumbs up

    Quote Originally Posted by Kazoo View Post
    Call me crazy... but could my pods be ok! (Sounds like a women going in for a breast exam!!)


    Highly doubtful if the car came with no documentation.



    Blower fan only operating on high means you need blower resistors.
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    11/1984 735i (10:1-265/6)
    Ford, MB, and GM round out the pack.



  14. #14
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    But why would the actuators work fine with the A/C and not with the heat? and where are those resistors? are they on the heater control board, or on the blower itself?

    There are not a lot of previous bills that came with the car - but I'm not sure that much work was every really done besides regular service intervals that are stamped in the book. The car is completely original and un-touched with 55k original miles - the drivers seat is as new!

    It spent its life in a garage and was never used in the winter, when the old timer died, his son wouldn't part with the car and barely used it. Every piece of rubber on the car is amazing, even under the hood - nothing is dried out or cracked.
    Attachment 618275
    Last edited by Kazoo; 12-19-2017 at 10:45 PM.

  15. #15
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    Different pods open at different times in different combinations via separate solenoids. If a vacuum circuit is inactive in one mode it may or may not be in another. I’ve found that if a vacuum leak is at a pod after a solenoid, and the applicable solenoid is closed there is no vacuum leak and the system can function normally. Opening that solenoid, opens up that vacuum leak. The system is pretty tricky. That’s why most of us go for the replace it all route. It probably needs it by this time anyway. Rather than spending hours diagnosing vacuum leaks over and over again, overhaul it now and enjoy for years to come.

  16. #16
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    I know I have to just start digging in, Ive read so many of these posts with all different answers to the same problem Im getting dizzy...Given it seems to be a typical problem its surprising there is not more of a process to address it ...

    Seems some suggests that the heater control wheels and push button selectors are the problem and to replace those, other say the actuators.... Im really trying to diagnose as best as I can the situation with mine and then start in the best place. I'm afraid that ill tear the dash apart, hopefully be able to source and replace the actuators -- spend a bunch of time and money and still have the same problem because it was the heater control wheels or something else etc...

    The one thing that sounds pretty definitive is that if the blower only works on high like mine, than the transistors are bad and new ones will fix that.. I ordered a pair of these as recommended on one of the threads by Hit Man.

    Do you know where they are located, how you get to them and how to replace them? Are they behind the heater control panel? Do they plug in or do they need to be soldered, what needs to be removed to do this, heater controls, center console or are they on the engine side of the firewall?

  17. #17
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    Thumbs up

    If you think you know more than Tim does about these climate systems, you are sorely mistaken. You do not have a simple fix, no one does. Trusting a 40 year old automatic HVAC system to work is like trusting a 40 year old condom to work. Wishful thinking.

    The TIS is available free, it shows where the resistors are located.
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    11/1984 735i (10:1-265/6)
    Ford, MB, and GM round out the pack.



  18. #18
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    Obviously I don't think I know more than Tim, I just bought the car and know next to nothing -- as is sorely obvious by my posts.

    I'm not sure what a free TIS is ??

    What I do know is that I could use to find a E23 forum that is geared for new comers to these cars...

  19. #19
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    This place IS geared for all people, especially when they take advice.
    http://www.bmwtechinfo.com/repair/main/
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

  20. #20
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    I think something to keep in mind is that this is a message board. We don't get the chance to talk through in great detail every point as we would in person, so the suggestions you get here are meant for you to take as very educated starting points, do some research, then execute and report the results. The more you do that you will find people offer up their phone numbers to talk through things in further detail. It is very much oriented for newbies so don't give up, just ask and get clarifications after you have done some research and tried some things suggested. When you do your research you will then be able to add value to the conversation, in turn further motivating people to help you with your issues.

    Additionally, some things that have helped me out over the years is to check the mye28.com board and the bigcoupe.com board for their discussions as well. A lot of the issues we discuss are well vetted there since the engines, transmissions, and other systems are very similar so the diagnosis can often help guide you if you can't find the answer to your problem on our board.

    I have had tremendous experiences with Hitman (Eric), and Timgal1234 (Tim) on the phone, and have benefitted from Jay, Justin, and many others from advice, part selection, upgrades, and just general conversation even though I have never talked to them on the phone. If you want help it is here; just be willing to accept that these guys know what they are talking about, and if you ask for advise and they give it, they are waiting to see that you did one of those things to see how it worked out before they go further.

    With that in mind, change those resistors and let us all know what the result was. That is a well documented and cheap solution for the issue you initially presented. If that works, great. If not, then come back and tell us and the very educated crew here will willingly guide you along. Keep at it!!

  21. #21
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    Thanks for the nice message - appreciate it.

    and good advice!
    Last edited by Kazoo; 12-30-2017 at 07:07 PM.

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