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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 01-21-2016, 12:18 PM
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Flybot Flybot is offline
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Location: Louisville, Ky
 
Join Date: Aug 2009
Posts: 1,006
Mein Auto: '98 528
Help Diagnosing Intermittent Heat

Now that its really cold the heater has decided to give troubles. Checked for operation of the aux water pump- it works. Center vent mixer dial on full hot. Cabin fan works normally in manual or auto.

I normally use the Auto setting. The car will increase the fan speed as the engine warms up until at at full blower, but no heat most of the time. Sometimes it will work normally. I have gotten it to work a few times by turning the fan all the way down to off and then back to auto. Also often when the cold air is blowing the footwell vents are closed and it seems to only blow out the defrost vents. It should be trying to warm my feet. Sometimes the vent diverter flaps seem to have a hard time deciding what mode to be in in auto- in other words unusual changing of which vents the air comes out of. Manual vent control works. Then today going in to work it was blowing cold and then went to normal toasty, then started to get just cool air again.

The fact that it can produce good heat tells me the heater core is good. I suspect the climate control unit or the heater valves. I read a thread on the X5 forum where dust buildup in the IEKA air sampler vents can cause erratic operation. Ill check that when I get home, but dont think it will pan out.

Anyone have any good diagnosis ideas? Thanks
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Last edited by Flybot; 01-25-2016 at 07:52 AM.
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  #2  
Old 01-21-2016, 01:02 PM
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mattmar1 mattmar1 is offline
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Location: Louisiana
 
Join Date: Dec 2014
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Mein Auto: 1999 5281 5 sp msport
when you go to max defrost (the upper right button in the panel) does it blow hot air on the windshield? has any work been done under your dash? the flapper stepper motors are individually addressed, if anything was taken apart, its not just a matter of putting them back and hooking them back up, each has to be put back in to the same position that they were removed from. also, your bowden cable from the vent center dial may have come loose or broken at either end. if the max defrost works, this might just be your problem.
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99 528i 5sp sport, vanos rebuild,coolingoverhaul,stripped/repainted/polished/recoated OEM BBS style 5 wheels, new paint , all int/ext LED's clear corners, all vac leaks fixed, eonon 5166, ECS short shifter, LED ae's and fog lights (clear), all brakes, fixed trifecta, rear control arm camber repair, new throttle body, ccv delete, but it ended up as a huge vac leak, returned to new stock ccv, new injectors, cloned and replaced dme.
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Old 01-25-2016, 08:00 AM
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Flybot Flybot is offline
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Location: Louisville, Ky
 
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Mein Auto: '98 528
Just a quick update: I think my heat issue is fixed, however I feel pretty dumb about it. I took the climate control unit out and blew out a lot of dust that was inside the sniffer vent. Reinstalled and went for a drive. Heat was working normally at first, then started to get weak. Then while waiting in a drive through line I got an coolant over temp light. WTF!. I got out of the line and shut down, and let it cool off, then managed to get home with minimal stops (temp would stay normal as long as I didnt sit and idle). I let it cool completely and did a coolant check and a bleed. It took about 1/2 gal. I was seriously pissed at myself for letting the coolant get so low. Ive had the car for 12 years and until recently it has never needed any fluids topped up between change intervals. I guess at 222,000 miles I need to be a bit more careful.

As a side note: even tho it took about a 1/2 gal, the expansion tank still had fluid in it. It looked like maybe 1/3 full instead of the 2/3 for "full". So you cant really use the expansion tank as a gauge for how much fluid is required.
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Last edited by Flybot; 01-25-2016 at 08:05 AM.
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