BMW and Mini heat diagnosis!
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BMW and Mini heat diagnosis!
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BMW and Mini heat diagnosis!

Your BMW ain’t so hot! (A.k.a. diagnosing heater problems.)Driving your BMW or MINI for a while in the colder weather, you may notice a degradation (or complete lack) of output from your  heater system. Causes of this lack of heat can range from worn parts to failure of new electronics. Most issues can be traced to either a problem with coolant flow or with the blower.Coolant Flow:1) Thermostat.Typical mechanical thermostat for early BMWsTypical electrically controlled thermosat for later BMWs and MINIsThe engine’s thermostat controls the engine’s temperature and keeps it from becoming too cool. A thermostat that is stuck open will cause the engine to run too cool to get the coolant hot enough to produce adequate heat. In this instance, you would tend to have more heat when you’re idling and the blower is set at a lower speed. One quick way to diagnose this is to watch the temperature gauge. Does it take a long time for the gauge to start to go up after a cold start? Does the gauge read in the middle of the range, as it should, after a few miles of driving, or is it below normal? If so, the thermostat may be stuck open.2) Water Control Valve.Typical water (heater) control valvesAlso referred to as a water valve or heater valve, this is the control valve for the flow of hot engine coolant through the heater core. More flow = more heat; less flow = less heat. On older BMWs, the water valve is operated manually via a cable; on newer BMWs and MINIs it is electronic. If the engine temperature gauge reads properly, as noted above, the water valve could be stuck closed, partially open or fully open. In this case, diagnostics are not as clear as with a faulty thermostat.•    If you can’t turn the heat off, you should suspect a faulty valve or a malfunctioning control cable or  electronic control unit.•    If you have low or no heat, the valve may be faulty, the heater core may be clogged, or the control cable or electronic control unit may be faulty. A mechanically controlled valve is relatively easy to inspect for operation of the control cable. (Refer to the Bentley manual for your BMW or MINI.) Electronic valves, however, cannot just be visually inspected. Typically, if all other functions are working properly (e.g. blower speeds, A/C, air direction control, etc.) the control unit will not be at fault. But one common symptom of a faulty electronic valve is that there is heat when idling, but as engine speed (and, hence, vehicle speed) go up, the heat goes away. A relatively quick way to decide if you have a valve problem or a heater core problem is to  bypass the valve. Remove the input and output hoses from the valve and use a plastic connector nipple or elbow to connect the hoses together. This will mimic a fully open valve. If you now have full heat, either the valve is faulty or the control for the valve is faulty. If all other heat and A/C functions are working properly (just no heat), then it is likely that the valve is faulty. If bypassing the valve makes no difference in your lack of heat, you are likely dealing with a clogged heater core.3) Heater Core.Heater coreThis is the actual heat transfer unit. Hot engine coolant flows through the core. The passages for the coolant inside the core are relatively small and can become clogged with age, especially if the coolant has not been maintained. You can effectively test the coolant flow through the core by disconnecting the inlet and outlet hoses from the water valve, in the engine compartment, at the firewall. Apply a garden hose to the inlet hose and start with a moderate water flow. The same amount of water entering the inlet hose should flow from the outlet hose. Slowly increase the flow. If the outlet flow is noticeably reduced, you likely have a partially clogged heater core.Blower problems:
Blower motor assemblyIf your BMW is experiencing problems with the flow of air from the blower, this could either be a faulty blower fan or a problem with the control. Symptoms can range from no air flow at all, to just certain speeds working, to erratic blower operation.1) No air flow. If there is no air flow and you cannot hear the blower running, it is likely that the blower motor is faulty. However, be sure to check the fuses. There is also the possibility that the blower controls are faulty. Access the blower (using the appropriate Bentley repair manual), which is typically not difficult, and disconnect the two wires from the motor. Use a voltmeter to test for voltage between the two wires, when the blower switch is on high (with the ignition switch turned on). If voltage is present, the motor is faulty. If voltage is not present, there is a problem with the blower controls.2) Blower only works on certain speeds or only on high. This is likely a faulty blower resistor pack or “final stage unit” (the electronic version of the older blower resistor pack). These units are typically not too difficult to replace and are addressed in the applicable Bentley repair manual.Blower resistor3) Erratic blower operation. This would apply to electronically controlled BMWs. The blower may go on and off, or vary its speed, with no input from the control unit. This is typically a failing final stage unit. This is very common on the later model BMWs (3 series 92 on with automatic heat/AC, 5 series 97 on, 7 series 95 on, X5, Z4, etc.). BMW has redesigned these units and we offer the new versions (below) for replacement. Again, replacement is covered in the Bentley repair manuals.Early style final stage unit - commonly called "the sword"Late style final stage unitIf you try all of these steps and are still having difficulty identifying which parts have failed, please call and speak with one of our phone reps at 800-535-2002. They’ll help you select the right part(s) to make your BMW or MINI “hot” again.Tags → BMW heater diagnoseBMW heater diyBMW heater dose not workBMW heater how toBMW heater inoperativeBMW heater problemsbmw no heatMINI heater diagnoseMINI heater how to,MINI heater inoperativeMINI heater problemsMINI no heatCategories → 1 Series Conv - E881 Series Coupe - E821600 / 2002 – E103 Series 77-83 - E213 Series 84-91 - E303 Series 92-98 - E363 Series 99-05 - E463 Series Conv 06 on - E933 Series Coupe 06 on - E923 Series Sedan 06 on - E903 Series Sedan 12 on - F303 Series Wagon 06 on - E915 Series 77-81 - E125 Series 82-88 - E285 Series 89-95 - E345 Series 97-03 - E395 Series GT 2010 on - F075 Series Sedan 04-10 - E605 Series Sedan 11 on - F105 Series Wagon 04-10 - E615 Series Wagon 11 on - F116 Series 77-89 - E246 Series Conv 04-10 - E646 Series Conv 11 on - F126 Series Coupe 04 on - E637 Series 02-09 - E657 Series 10 on - F017 Series 79-87 - E237 Series 88-94 - E327 Series 95-01 - E387 Series Hybrid 11 on - F047 Series Li 02-09 - E667 Series Li 2010 - F028 Series - E31Bavaria Sedan - E3CS Coupe - E9MaintenanceMINI Clubman 08 on - R55MINI Cooper & S 07 on - R56MINI Cooper & S Conv 05-08 - R52MINI Cooper & S Conv 09 on - R57MINI Cooper 02-06 - R50MINI Cooper S 02-06 - R53Tech TipsX3 04-10 - E83X3 11 on - F25X5 07 on - E70X5 99-06 - E53X6 07 on - E71X6 Hybrid 11 on - E72Z3 96-03 - E36/7Z3 Coupe 98-03 - E36/8Z4 09 on - E89Z4 Coupe 06-08 - E86Z4 Roadster 02-08 - E85

13 Comments to BMW and Mini heat diagnosis!:

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drury lane on Friday, February 19, 2016 12:51 AM
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Reply to comment on Monday, January 14, 2019 6:49 AM
It is indeed hard to choose between a BMW and a Mini Cooper. Both of these brands are great producers of cars. They have a line of quality luxury cars which can satisfy someone that has a taste for great cars. In my honest opinion, I think a BMW would be much better if you are in a city with minimum traffic and clean streets. A BMW would be a choice for businessmen and people with a busy urban lifestyle.

Anonymous on Monday, March 27, 2017 10:55 PM
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Top IT Company in India on Friday, April 07, 2017 2:33 AM
Thanks for the post.
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Adison on Friday, June 23, 2017 7:26 AM
To determine the causes of heater system issues in a vehicle such as BMW or MINI requires depth technical prowess. Malfunction of some parts lead to deterioration of heater system’s functionality. One cannot easily identify the defunct part; it needs proper diagnosis. So, it is suggested that regular checks keep such incident at bay. A layman does not know the inner mechanism of his expensive car. So, he must make an appointment with a skilled professional at regular intervals.
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