My car fan runs on 2 speeds – can I replace the radiator fan resistor?

ANSWER : Hello – I believe this is normal behavior, and handles cooling the engine down appropriately (i.e. fan speed changing based on how hot the engine was when running) upon shutdown. There are problem cases where the radiator fan runs on high speed all the time, and in some cases doesn’t shut off as it should. If you believe this behavior is incorrect, I would recommend having an electrical components are not working inspection completed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, provide a deeper diagnosis of this problem, give you an accurate assessment of damage and cost estimate for repairs.

ANSWER : There are reports that the replacement alternators will not communicate with the engine computer and will not charge correctly. I recommend using only the manufacturer approved replacement part. It can be new or remanufactured but approved for use in the vehicle. Some lower cost alternators on the aftermarket will have charging problems since they will not communicate with the ECM on the vehicle and will stop charging.

ANSWER : The shaking could be the result of a number of issues, including the engine having a misfire (not firing on all cylinders). The radiator replacement would not have created this condition. The vehicle should be inspected in order to diagnose this issue. A YourMechanic certified mechanic can come to your home or place of business to perform a car is shaking or vibrating inspection on your vehicle.

ANSWER : The control circuit for the fans needs to be checked. For example, there is usually a condenser fan relay in the A/C electrical controls. There could be a fault with that relay and/or wiring problems, perhaps even just a loose connection, blown or loose fuse, and so forth. To resolve something like this, the recommended service is an electrical component diagnostic. If you request that diagnostic service, the responding certified mechanic will get the problem pinpointed and resolved. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

ANSWER : First off, yes your vehicle does have a timing chain. It is good that all that maintenance has been performed recently and should carry you for many miles. However, if you cannot verify the age of the coolant and fuel filter, it may be a good idea to replace them both even if they "look" good. One item you failed to mention is the brake fluid. Brake fluid is hydroscopic – it absorbs moisture. When it does, it’s boiling point is reduced which can lead to brake fade or loss, and reduce the life of components like anti-lock brake pump which can cost $2-$3000 to replace on some vehicles. Especially when it comes to vehicles equipped with anti-lock brakes, it is a good idea to have the brake fluid flushed every 2-3 years, regardless of mileage. Have a certified technician perform your maintenance needs like flushing the brake fluid for many miles of trouble-free driving.

ANSWER : A broken wire can generally fixed, but if the break is too close to the connector, you may want to replace the connector itself. If there is any corrosion inside the connector, then definitely replace the entire connector and the component it connects to for the best result. Consider having an experienced technician, such as one from YourMechanic, come out and take a closer look to offer a more personal diagnosis on the radiator fan.

ANSWER : Your vehicle fan is controlled by two different relays in the engine compartment fuse box. One is for low speed and the other is for high speed. The ECM controls both of the relays. The wires to the cooling fan motor are black (ground) brown (high speed) green with white stripe (low speed). With the engine running and the A/C turned on, check for power getting to the low or high power wires to the cooling fan motor.

If you do not have power to the low power wire, then try to replace the relay first. You may be able to temporarily swap the high and low speed relays to test to see if fan is coming on with A/C on. If it does, then try and replace both relays since they may both be burnt. If you find you are getting power to the cooling fan motor but it is not turning, then you have a defective motor. If you do not have power and the relay swap did not work, then you will need to have the computer checked to see if its able to turn on and off the fan using a dealer scanner. The problem is most likely the relay or fan motor.

ANSWER : Your question makes me think of a case I ran into a few years ago. The owner had modified his car but when he installed his fans, one of them was wired backwards so the fan ran in reverse. The two fans were fighting each other which was just like having no fan at all, so the car heated up while it was sitting still then it cooled off when moving. Check the rotation of both the fans before you check anything else. If that’s OK, you may be able to track down the problem with a non-contact thermometer, follow the course of the coolant with the beam. The radiator should be about 30 degrees or more cooler at the exit than at the entrance. If you need help with this, contact Your Mechanic. They can send a technician to your home to check out your overheating problem and let you know what can be done for it.