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No Heat

Discussion in 'E32 (1988-1994)' started by chazzone, Jan 1, 2009.

    chazzone guest

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    '89 735i, and I have no heat. I have hot coolant going to the heater core, but none returning. I checked the ohms on the interior air sensor, and it seems to be in need of replacement, but I think I should still be getting heat if I have the temp selector set all the way to the warmest setting. I'm getting some power to the valve, but not sure what it should be.

    Any thoughts?

    Thanks,

    -zz
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    mooseheadm5

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    May need a heater valve. They tend to fail in this fashion.

    chazzone guest

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    Heat

    Since I posted, I've been out doing some more bleeding of the system, and I'm getting some heat now. I seem to be only able to get her to take about a quarter cup at a time by squeezing the upper radiator hose (also checking the bleed screw from time to time and only getting a few bubbles) This sure is tedious. Any suggestions on a better procedure?

    Didier guest

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    Sounds like a heater core giving out. My '88 had / has a similar problem. The mechs say it is shot and needs replaced. Took it to my local dealer twice for estimates. $874 & $1209 to replace the heater core ($179 - $319 depending on which dealer you talk to), fluids (BMW Antifreeze is $24 a gallon), and gawd awful labor for a 8 - 10 hour job.

    chazzone guest

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    I think Moosehead is probably on the right track (thanks btw). When a heater core fails, it usually leaks, while the valves tend to get stopped up.

    I have good heat from one defroster, and some heat in the other, so flow is obviously the issue.

    I'm probably going to look around for a used valve, and disassemble and clean it, then swap it in.

    BTW, I realize that it is heretical, but I don't see any reason to use BMW anti-freeze in an '89 735i. If I'm missing something here, then please enlighten me, but Prestone Extended Life anti-freeze changed regularly (every 2 years) should be just fine.

    Thanks again,

    -zz
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    mooseheadm5

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    If you flush it, feel free to use any quality low phosphate antifeeze. As for the valve, you should get a new one if it is bad, but you need to try to test the old one. If the valve is not getting the correct power and ground signals, it won't work. I don't have the wiring diagrams in front of me, but I'll see what I can find at home on disc.

    chazzone guest

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    I have the wiring diagrams (good ol' Bentley), I just don't have the proper voltage values.

    I already did a flush, and I use Prestone Extended Life 50/150. Phosphate is not as big an issue here in America as it is in Europe. Their water is extremely hard, and that's what breaks down the anti-corrosion package, and why BMW recommends a low/no phosphate coolant.

    New is always better than old, except for the outrageous money some places want for one of these valves ($560! You have to be out of your mind!) I know they are available for less, but that is the regular retail price on that item, and I'd build my own valve before I paid that ransom.

    Right now it's getting by, and I'd like to make sure the voltage is correct, so if you run across those, I'd appreciate the post.

    Thanks,

    -zz
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    mooseheadm5

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    Unfortunately, the E32 valves are not rebuildable.

    chazzone guest

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    It depends on what shape they're in. You can certainly access everything you need to, and if it is a simple matter of them being clogged with sediment, etc, they can be cleaned up just fine, as long as the solenoids are in good shape and the valves/seals aren't too corroded.

    I'm an old farm boy, and learned to make the things I needed and fix what I had. You might be surprised what a guy can do with some time and elbow grease. Heck, for $600, I could make a great set of brass valves with solenoids to replace the plastic factory units. It's just two vales, after all, not rocket science.

    -zz
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    mooseheadm5

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    mooseheadm5

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    3 pin connector on the valve. Power comes from fuse 21 and goes directly to pin 1 on the 3 pin connector (green wire, brown stripe) when the heater control is set to automatic. Grounds are pin 2 (right valve) and pin 3 (left valve.) When set to max heat, the power is interrupted so there is no power to the valve at all and it should be wide open. If the diaphragm fails, water flow can close off the valve (it is supposed to fail open, but does not always.) The climate control computer pulses ground to close off the valves in auto. Armed with that, you should be able to get the valves to open if they actually work any more.

    chazzone guest

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    Thanks for that. The price from Bimmerspecialist for a replacement is more reasonable, and better than i'd seen before.

    I had power to the valve at max heat... kind of scratching my head at that, but I'll go back and check tomorrow afternoon. Could be that I have more work to do (does it ever end? ha )

    Thanks again,

    -zz
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    mooseheadm5

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    Well, it is possible that it does not work the way the wiring diagram says (it has happened before.) If you have power to the valves at max heat (you feel the click on the temp wheel) then you should not have any ground. If you have power and ground, you may have a problem with the thumbwheels and then the easy test is to just unplug the valves and see if you get full heat.

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