How can I repair Rheostat on my car ventilation fan?
Rheostat is not something that you can fix but here in this article we will give you some "how to override" if you have this problem and you need some fast solution.
You can repair rheostat only if all resistors works and you have problem thermal diode which is part of rheostat too.
What is rheostat purpose?
Rheostat is adjustable resistor which consist of 2 or more resistors. Whit this component you can control current that flow from source to some device (fan motor for example). In automobile you control fan speed with rheostat.
You have as much resistors in rheostat as much you have fan speeds on your vent fan.
You know what happens when you drive without fan and outside is cold weather, right? So lets imagine that you are in situation when outside is cold and your fan won't work.
What to do if you are in hurry or in the middle of nowhere and you have no time or possibility to wait for car service to come?
You will probably try to fix fan so here is what you need to do if you have no other choice:
1. Check fuse for car fan
This is first step and if you found that fuse is OK go to step 2
2. Try to start fan in other speed level
If you have damaged rheostat where some of it's resistor fail and some working then some of fan speeds will work like nothing happened and some will not work at all. In this case you just pick one of the working positions and go to the first service.
If you try every fan level and none of them work then go to step 3.
3. Do a switch test
Try to check your control switch for any kind of failure, if it is OK go to next step.
4. Open your hub and try to get to the fan.
It is hard but if you must then do whatever you need to do.
You'll see one wire connection near fan. Disconnect your fan and search for rheostat. Maybe you can get to the rheostat without disconnecting fan, that depends of your car model.
When you reach to the rheostat look for thermal diode and just do short circuit between two endings of diode with some isolated wire.
While you doing this look for any lives or some other dirtiness around fan and clean it. That probably cause your trouble with fan.
When you short circuit diode try to do "short fan start". If fan works that drive to first service to change rheostat.
Thermal diode fail be cause your fan motor was to much overloaded. All that dirtiness and leaves cause that and thermal diode react to protect fan motor. Other reason can be fan motor itself. Maybe he is mechanically damaged.
Anyway if this helps it is good for you if not then your fan motor is dead for sure and you must wait for service to come. But just to know this is rarely happens and mostly thermal diode reacts and save other parts of system.
Conclusion
Rheostat is not cheap element and if you can try to fix it by yourself. You can search for diodes in electronic shops and they are cheap. Much more cheaper than rheostat.
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