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Ron Stygar Carl Buckland Dale Beuning Forums Help
From bmwuucdigest_at_topica.com From: Pearson-Franks Family <pearsonf_at_pop.halcyon.com> To: bmwuucdigest_at_topica.com Date: Thu, 23 Dec 1999 18:55:28 -0700 Subject: Re: E28 Heater Valve Repair Kit Shane: Here are specifics put together in response to a similar query. I go into gory, generic detail; skim what is not of interest. In the event that you are having trouble controlling the interior temp in your E28; read on! This troubleshooting guide hits the modes of failure that can result in:
The heater control valve is mounted on the firewall in the engine compartment, just inboard of the vacuum booster for the brakes. It has a two pin electrical connection on the top, and two hoses on the bottom. The 'top' is secured with 4 straight-slot screws, which can be removed with a little torquing around of the mount for the assy. You can then extract the 'core', which, if the system is not under pressure, will not leak coolant (quite a blessing, really!). Anywho, the core is merely a solenoid that when 12v is applied to it, retracts, pulling up a plunger. The hydrodynamics of operation are a little more complicated than that, but the parts that wear out are the rubber seals. Look for any deterioration, or slits in the diaphram part of the seal. Any leakage will be passed as hot water. This core is available from dealers; and interestingly not from most mailorder parts houses. The part number is: 64 118 390 132 with a reported retail of $47.45. It is much cheaper than replacing the whole assy, which is usually OK anyway, not counting the seal! If your seals look fine (unlikely unless already replaced) then it gets messier. There are two sets of thermistors; one just above the driver's left toes, and one more or less straight above the driver's right toes, but buried in the guts of the heater itself. The left one is accessed by pulling the driver's underdash panel. It has a three-wire connector and a tiny vacuum line. The line sucks cabin air past two thermistors on a tiny copperclad board to sample interior temp. If you use an ohmmeter among the three leads, you should find 30ish ohms on one leg, and a couple of hundred on the other. Short = bad, open = bad; the actual values are not critical as a troubleshooting issue. The other one is more of a bear - since you already have the underdash panel off, look above the accelerator pedal and find a two-wire device secured to the heater case with a single screw. Unplug the connector, remove the screw, and extract the several inch long thermistor mount. For reasons unclear to me, the soldered connections to this thermistor just let go. Probably some sort of esoteric electrolytic reaction in the presence of the various metals and chemicals available, but easily amenable to resoldering! This device will measure at a couple of Kohms, as I recall. Last but not least, if all this checks, or is repaired by now, the last culprit is the control know assy itself. It has a 6 or so pin connector to it, and the electronics in it have died on occasion. Save this possibility 'till last, as it is obnoxious to replace, not testable in any way known to me, and is relatively expensive ($50ish) to replace. Hope all this helps! Larry F.
>Date: Wed, 22 Dec 1999 10:00:56 -0500
Pearson-Franks Family
> Date: Wed, 22 Dec 1999 10:00:56 -0500
> only buy the entire assembly? For some reason I thought that was the
> also thought someone once said that the same part (repair kit) could be
> konked out on my 535is on Saturday night, in Philadelphia, the day before
> to drive 9 hours home, freezing cold. Sheesh. Anyway, any help with this
> appreciated, and does the kit still cost $30. I'd like to get one local
> don't pay shipping for one part, not to mention that I need it before this |
