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Discussion Starter #1 (Edited)
E36 Heater / Overheating / Underheating / Climate Control / Air Conditioning / HVAC / Guide plus Common Faults & Repairs

We seem to get a lot of Heater / Climate Control questions on the forum so I thought I’d try and pull together all the knowledge into this guide. As ever please PM me if you have any additional info.

This is not the place to ask questions. If you have read this carefully and still can’t work out what to do post a question in the E36 forum http://www.bimmerforums.co.uk/forum/f17/

Overview There are 5 types of heating & ventilation used in E36s –

1) Manual Heating & Ventilation (Pic 1) A similar layout is used on the Compact




2) Manual Heating & Ventilation with Air Conditioning (Pic 2) A similar layout is used on the Compact with the air con switch to the side.



3) Automatic Climate Control (Pic 3) Not available on the Compact

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4) Automatic Climate Control with Automatic Air Recirculation Control (AUC) (Pic 4)



5) BMW also offered basic air con as a retrofit option for left hand drive vehicles. They called this the “Economic Air Conditioning System”.

Manual Heating & Ventilation with or without Air Con

These systems are generally trouble free compared to Climate Control, however most of the common faults below apply to both systems.

Automatic Climate Control with or without AUC

If you have just acquired your E36 and don’t understand how to work the Climate Control or what the buttons do then have a look in the owners manual. If you don’t have one you can download the USA owners manual here… Download BMW E36 Owners Manual in English | BMW E36 Blog Pages 88 to 92. As far as climate control is concerned this is the same as the UK owners manual.

What is AUC? Automatic Air Recirculation Control is basically a more sophisticated version of the fresh air / recirculated air switch. When correctly set it will automatically stop drawing in outside air if it senses there are “pollutants”. I’m not sure exactly how it does this but feel free to PM me with an update if you know.

Heating / Cooling / Ventilation / Climate Control Faults & Fixes There are a number of common faults with these systems...

1) No cold air – This is usually down to the air con system requiring re-gassing which should cost you around £40 at most garages. It is recommend that you run your air con at least once a month for at least 15 mins (even during winter) to ensure that the components don’t seize up. It will also keep the system from getting a musty smell. Common mechanical faults due to lack of use are… · Failed Fuses, Relays or Sensors· Failed Compressor Pump· Seized Compressor Pump Magnetic Clutch· Snapped or Slipping Compressor Pump Belt· Seized Puller Fan· Leaking or damaged air con pipework

2) No hot air / No hot air at idle – If the car is getting up to normal temperature and stays there without overheating this is usually down to an air lock in the cooling system or blocked/inoperative flow valves. Ronnie has answered both these issues here… http://www.bimmerforums.co.uk/forum/f17/1995-e36-328-coupe-heater-controls-t57515/

One final potential cause of this is a blocked heater matrix / core. This can be removed and replaced from inside the car behind the glovebox. If you are not getting hot air from the face vent and you have Climate make sure you have the dial under the vent set to red instead of blue. If you have standard heating you cannot get hot air through the face vent, see here... http://www.bimmerforums.co.uk/forum/f17/1997-e36-318i-hot-air-problem-t890/page2.html

3) Overheating of Engine - There are a number of very common and less common faults that lead to E36s overheating...

a) Air lock - Follow Ronnie's guide in the above link
b) Water pump - Early E36s had a plastic impeller in the water pump and this disintegrates over time until the pump no longer circulates the water. When this happens the hot water stays near the engine and none reaches the heater box. This can also lead to overheating either at idle or when driving.
c) Failed viscous fan - If the fan clutch (the middle bit) fails the fan won't spin properly and won't cool the engine. Replacements are easy to get. There are a few guides to help you... http://www.bimmerforums.co.uk/forum/f17/bmw-e36-325i-coupe-1994-viscous-fan-nut-t12095/
d) Blocked radiator - Regular flushing of the system should prevent this, however there is no easy way to check other than to remove the radiator.
e) Thermostat jammed shut - Not very common but it does happen.

3) Underheating of Engine - The thermostat is the first thing to check / replace as it has probably jammed open. After this check the viscous fan has not seized or the electric fan (if your model has one) is not running all the time.

4) Climate Control Head Unit switches itself on & off randomly - This problem is caused by a capacitor overheating in the unit. It becomes hot and won't carry the charge, so the unit switches itself off. It cools down and starts to carry the charge again so the unit switches itself back on. The cycle repeats until the capacitor is so hot the unit stays off permanently. Some times it will recover when fully cooled, other times it completely blows and the unit won't come back on. All credit to Mr Swope in the USA for his excellent step-by-step guide on how to fix this problem….. Richard's Web Site Several electronics places in the UK carry these capacitors including Maplin. I’ve done this fix several times and used item No 220450180746 off eBay (6 for £2.24) The voltage rating is not as important as getting the right capacity – I used 63 volt without any issues. Note: 470nf (nanofarad) is the same as 47uf (microfarad) While you have the unit apart its a good time to clean the duct and the little fan that draws air past the interior temp sensor (the little blue blob you can see on the right of the unit) If this gets blocked with dust the climate system can’t get an accurate cabin temp reading. It might also be worth putting a small drop of light oil on the fan bearing if it squeaks or doesn't run freely. If you are not confident with a soldering iron there are several places advertise on the web and eBay that will fix your unit for around £20 on an exchange basis.

5) Poor air flow – Both manual heating & climate control unit have a dust filter, sometimes called a pollen filter, microfilter or a HVAC filter. Often this is neglected during servicing and can have been in place for many years becoming clogged with dirt and debris, sapping the airflow. There are three types of filter….

Climate – A flat panel filter (Part No 64 11 9 069 895) fitted under the dashboard, accessible from the driver’s footwell (RHD only) http://www.bimmerforums.co.uk/forum/f3/1997-e36-328i-pollen-cabin-micro-filter-t55344/

Non-Climate including Compact – Two dome shaped filters (part no 64 11 1 393 241) fitted in the scuttle next to the fan….
http://www.bimmerforums.co.uk/forum/f3/e36-1995-316i-compact-pollen-filter-location-this-t53047/

Compact with air-con – This has an additional small flat panel filter. I’ve not found a guide /location for this yet but here it is….. http://bmwfans.info/parts/catalog/E36/Compact/Europe/318ti-M42/browse/heater_and_air_conditioning/microfiltre_microfiltrecover/

6) Blower fan doesn't work, operates intermittently or at low speed – The speed of the blower fan is controlled by the Final Stage Resistor (FSR), sometimes called the “hedghog” or "porcupine" in the USA. There are two solutions, replace or repair -

Replacement - Bigedd9990 has written the following excellent guide on how to change the FSR…
http://www.bimmerforums.co.uk/forum/...-guide-t15242/ There is a second type shown here… http://www.bimmerforums.co.uk/forum/...-stage-t66524/

Repair - The common failure is down to weakened solder joints but you need to scrape away the sealant to get to them, there is a guide here...
http://www.xoutpost.com/bmw-sav-forums/x5-e53-forum/75414-final-stage-resistor-fix-diy.html

If you have checked the FSR and all is well it could be that the blower fan itself has failed. There is a good DIY guide to replacement here... http://www.dvatp.com/bmw/hvac_blower

7) Hot air or cold air always blowing from the face vent in centre of dash (Climate Only) This vent works independent of the heating controls (i.e. you can have hot air on your face but cold air coming out of the foot vents) so you need to ensure you have the second dial under the vent set to either hot (red dots) or cold (blue dots)

8) Hot air or cold air regardless of heater setting Check the operation of the heater valves in the engine bay near the bulkhead (under the windscreen). They are electrically operated and if they jam open or shut you'll get hot or cold air regardless of the setting.

Converting Manual to Automatic Climate Control A commonly asked question is “Can I convert my car from Manual to Climate?”. The answer is yes, but before you get excited it is a long and complicated job - unfortunately you can’t just swap the head unit over!

Manual to Climate – This is the hardest conversion as you have to fit everything

Manual with Air Conditioning to Climate – This is easier as you car already has most of the required air con components There are three main things to do…

Air Con - Clearly if your car doesn’t have air con and you want Climate Control you’ll have to fit all the air con parts and the associated pipework & wiring then get it gassed up.

Heater Box & Vents – The air distribution flaps in cars with Climate Control are motorised, plus it has the cooler element from the air con so you need to fit a heater box from a car with climate.

Wiring – There is a significant amount of extra wiring for Climate Control, plus there is a separate control unit that links to the DME

Here is the shopping list… Climate head unit, Climate unit wiring harness cut back to the loom, Climate control unit, Dash centre air vent, Complete air box & fan assembly & wiring Radiator with electric puller fan & wiring, Condenser & hoses, Evaporator & hoses, Compressor with mounting bracket, belts & hoses, Engine pulley for use with compressor. To fit these items you'll have to remove the steering wheel, glovebox, centre console, instruments and the entire dashboard, heater box & fan assembly, all the air ducts, drain the cooling system, remove the front bumper, grille, radiator & fan coupling. You'll also have to do some major work on your wiring loom and fuse box. Here are the links for the dashboard and heater box removal to give you an idea of what is involved… Sphinx’s Dash Removal Guide – http://www.bimmerforums.co.uk/forum/f3/e36-dashboard-removal-guide-t38712/ My Heater Box Removal Guide - http://www.bimmerforums.co.uk/forum/f3/e36-heater-box-seal-replacement-to-fix-wet-t40364/ If you are feeling brave and still want to go ahead I recommend that you find a donor car (same age, engine, etc) with the full climate control system at a local breakers and remove everything carefully yourself. This way you'll have every part you need and more importantly you'll learn about the fitting process (in reverse) into the bargain. Just to prove it isn’t impossible here is a link to someone that has done it… http://www.bimmerforums.co.uk/forum/f9/1996-e36-328-climate-control-and-on-board-t18239/

Hidden Test Menu

Finally, here is some info on how to access the hidden test menu from a guy called Richard Nott. It seems that this works for some people and not for others. There is a suggestion it only works on pre facelift cars (before 1996). Please feedback on this if you can get it to work

Press the "AUTO" and "REAR DEFROST" buttons simultaneously. 12 displays are available. Toggle through them by pressing the fan rocker (+ or -) switch.

1 Interior Temp Sensor
2 Exterior Temp Sensor
3 Left Heater Core Sensor
4 Right Heater Core Sensor
5 Evaporator Temp Sensor
6 Engine Speed Input
7 Road Speed Input
8 "Y" Factor Value
9 Fresh Air Flap Position (%)
10 AUC Sensor Voltage
11 Battery Voltage
12 Software Version

To exit the display function press the "RECIRC" and "AUTO" buttons simultaneously, or turn off the ignition.

Note: 1. Decimal Points are not shown, Hence 75.5% is displayed as 755. 2. All Temperature displays are in Centigrade3. Negative values are indicated with minus sign

Enjoy!
 

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I'm on option 2. Looks like I need to look at my valves!
 

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Excellent info guide. Going to swap mine over from standard blower control to AUC air-con this summer...bit late I know but managed to source all the parts from a donor car however I have to match the wires up and replace the fusebox with the donor one as it includes the necessary relays???
 

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This is a great guide.

But.

I have replaced the FSR, the dash unit that controls the heating/AC, the Fan Motor itself and all the vent lines.

But still the fan is intermittent.

Will work for a day without a problem, blowing from the turn of the key at numerous stop/starts, but then it will just suddenly stop for a week or so without blowing at all, then for no reason start blowing fine for whatever amount time it fancies.

It is not temperature [inside or out] dependent.

It is entirely random.

I have heard that there is on some models another resistor within the core of the heater, is this true and can this be the problem?

There is continuity right through to the fan motor and if I apply a second battery to the terminals it blows happily enough.

Is this a new and subtle fault?

E36 1997 conv M3
 

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Good stuff

For the first time , I found some really useful info on A/C, I have a small 95 hatch and no matter if I press the air flow or not, hot air always getting inside and it is very annoying. I now know that there is a vent inside the bonnet that I can check. Also when I press the air con it makes a noise that it is doing something but according to mechanic the compressor is fault. i have to get 2nd hand too and replace it.
 

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Air flow from mine isn't particularly strong, will be checking it out in accordance with this guide later this week!
 

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E36 Climate Control review - 470nf (nanofarad) is the NOT same as 47uf (microfarad)

This is a superb source of info. Thanks for putting it together.

I thought I'd better bring it to attention that 470nf (nanofarad) is NOT the same as 47uf (microfarad). I microfarad = 1000 nanofarad. This means that 470nf = 0.47uf. A value of 47uf would be 100 times too large! I assume it was just a typo missing the '0.'?

I have my climate unit in bits and was about to solder in a 47uf cap. It was when I checked the polarity that I spotted the problem. The 0.47uf cap is not polarised.

cheers
John
 

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Can you update the original post, specifically the reference here:

"If you have standard heating you cannot get hot air through the face vent, see here...

1997 E36 318i, hot air problem."

Because that link is dead.
 

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Hello , is posible to swap manual heating and ventilation unit (pic 1), to automatic air conditioning unit(pic 3)? Im not thinking to swap fully air conditioning, im thinking swap just units, so functions will stay the same as on manual heating just operating with air conditing unit(pic 3) , please info? :)

Thanks a lot..
 

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Check relays no 9, 13, 14, and 15 relay could work intermittent.

Check fuses 16, 20, 23, 31, 39, 41, and 45 and correct strength.

I might be mistaken, but the fan should only work when needed. In cold weather the fan will work less and much more in hot weather. If you want wiring diagram Pm me with year and model no

Good luck
 

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cost of replacing ac capacitor

Hey billywhizz, From your knowledge of A/C maintenance, i think you should must have some info about replacing an AC's capacitor. I've just paid $475 a local co. to fix my Air Conditioner. He replaced a blown capacitor on the roof portion of the system, and did it in about 5 minutes flat. I was desperate at the time, but now I've cooled off and I've kept the part he replaced, I'm not so sure this isn't a total rip-off. I have no idea how much this part should cost. I'm happy to pay a pretty hefty emergency call-out fee, but I'm not willing to stick with a 10,000% markup on a $5 part. So in reality, how much does one of these things cost? $5, $50, $200? I don't have the component knowledge to go find a price on the web.... but I'm getting a sinking feeling... :-(
Thanks in advance.
 
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