Symptoms of a Bad or Failing Thermo Coolant Fan Switch

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A coolant fan switch is a small and very simple switch comprised of typically two wires. This switch is configured to work based upon the temperature of the engine. As engine temperature rises to a specific threshold, the switch is activated powering on the coolant fan. The coolant fan will continue to run until the engine temperature cools down to a specific predetermined level. Once the temperature reaches this cooling stage, the coolant fan will shut off. Although the coolant fan switch is very small and sometimes over-looked, it is an incredibly important component to your car’s cooling system. Think of this switch as the “gate keeper” to the temperature regulation in your vehicle’s engine. There are many other engine systems which are also indirectly affected by the operation of this switch, but in the context of this article we will focus on its relation to the operation of the coolant fan. Several symptoms may point to a bad or failing thermo coolant fan switch.

1. Engine overheating

Engines generate an enormous amount of heat and as a result are subjected to very large temperature swings if this switch does not operate effectively. When this happens, the result can be extremely damaging, resulting in thousands of dollars in engine damage. A common sign of a faulty switch, which can also be alarming, is that the switch will simply not turn the fans on at the predetermined temperature level resulting in engine heat climbing above what it should be in order to run effectively. When temperatures exceed this threshold, many other components begin to fail, in addition to the performance of the engine declining.

2. Check Engine Light comes on

Fortunately, when this happens your Check Engine Light will be on and depending on the model of the vehicle, an additional “engine hot” symbol will also appear in your dash. This is a very critical time to get the car home or to a place where it will not be driven until it is looked at. In other cases, the switch will turn on and stay on well past the cooling temperature threshold, resulting in the fan running even when the engine is off.

2. Broken or shorter signal wire

As mentioned earlier, there are two wires inside the switch. When one of these is broken it can cause them to ground intermittently, which will cause the fan to also work intermittently. When either of the two wires short out, this can cause intermittent operation as well, again resulting in intermittent responses to the fan turning on or off unexpectedly.

Since this is an electrical component, when faulty there is often times not much predictability as to when it works and when it does not. As mentioned above, the thermo coolant fan switch is a very vital piece to your engine’s life and is a very inexpensive part to replace. As such, our recommendation would be to have an expert mechanic from YourMechanic come to your home or office to diagnose the problem.


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Rigoberto

9 years of experience
706 reviews
Rigoberto
9 years of experience
Chevrolet Equinox - Brake Pads Replacement (Rear) - Niles, Illinois
Rigo was great! He got there early, finished the job early, left everything clean. He changed my rear pads and rotors. The original quoted time was 90 minutes, he was done in about 60. He knows what he is doing and I am recommending him to all my friends and coworkers.
Mercedes-Benz C250 - Brake Pads Replacement (Front, Rear) - Chicago, Illinois
Rigo is a maverick hands down. Don’t take your car for work elsewhere. Especially great at Mercedes—this guy knows his profession! I will be using him for everything related to my car going forward.

Arturo

25 years of experience
35 reviews
Arturo
25 years of experience
Kia Forte - Brake Pads Replacement (Front) - San Diego, California
ARTURO is great! very professional , fast, replaced my front brake pads and oil an filter change. everything now works and works well. Brakes have much improved stopping power and engine is smooth and quiet.Arturo is also kind and thoughtful. "Your mechanic" is very fortunate to have Arturo Lopez represent your company. I enthusiastically recommend him and "Your mechanic> as a fine operation Best regards to the Team Peter Marto
Nissan Maxima - Brake Pads Replacement (Front, Rear) - San Diego, California
Arturo was prompt and completed my brake repair, including new rotors in a very efficient manner. I am very pleased with the quality of the work and the parts and will definitely look to have him service our other car in the near future.

Scott

32 years of experience
345 reviews
Scott
32 years of experience
Lexus IS250 - Brake Pads Replacement (Rear) - Denver, Colorado
Always on time, speedy, professional, and pleasant to interact with. The work is always consistent and we'll done. I can't reccomend Scott highly enough!

Michael

10 years of experience
15 reviews
Michael
10 years of experience
Nissan Sentra - Brake Pads Replacement (Front) - Conyers, Georgia
He was promptly on time and got the job done efficiently in a timely manner. I really appreciate the rapid respone on getting the job done! I would most definitely use this service again.

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