How to Replace the Heater Fan Switch or Relay
Content
The motor switch on your heater and air conditioner fails when the switch gets stuck in certain positions or does not move at all.
This can be frustrating when you turn on the air conditioner, heater, or defroster and no air comes out. If you drive a car made in the 1980s or early 1990s, there are a few things you can do. Later vehicles often have fully integrated climate control systems that require specialized computer hardware to diagnose accurately. But earlier cars still have many parts in their heating and air conditioning systems that the owner can fix and repair. Despite differences from car to car, there are a few common elements in the work.
Some common signs of a blown fan motor switch failure are if the switch only works at certain air settings, which happens when the contact wears out, or if the switch sticks or sticks frequently, indicating the switch is not working properly. If the knob on your system is not working, this could be a sign that the knob is broken, even though the switch is still working.
Part 1 of 4: Evaluate the system
Necessary materials
- Owner's Manual or Repair Manual
Step 1. Determine which system is installed in your vehicle.. Your workshop or user manual will help here.
Some cars were available with manual or automatic climate control. If it's a fully automatic system, there may not be a switch you can change. Fully automatic climate control usually has a temperature control knob and some kind of automatic setting.
In most fully automatic systems, the fan switch is combined with the control panel, which is replaced as a unit. These panels are usually quite expensive, so careful diagnostics and special computer software are required to make sure you're not throwing away a lot of money by replacing one of them unnecessarily.
A manual system usually has a few simple switches and buttons that are often easy to diagnose and replace.
Step 2: Test the system. Try all fan switch positions and note what happens.
Does it work at some speeds and not at others? Does it intermittently if you jiggle the switch? If so, chances are your car just needs a new switch. If the fan is running at lower speeds but not at high speed, the fan relay may be the problem. If the fan doesn't work at all, start with the fuse panel.
Step 3: Check the fuse panel.. Find the location of the fuse and relay panel(s) in your workshop or in your owner's manual.
Be careful, sometimes there are more than one. Make sure the correct fuse is installed. Pay attention to the condition of the fuse panel. Many European cars of the 80s and 90s were built with fuse panels that were not originally strong enough to withstand the high temperatures in the fan circuit. The repair involves installing factory upgrades to keep the fuse panels up to the task at hand.
Step 4: Replace the fuse. If the fuse is blown, replace it and then try the fan.
If the fuse blows immediately, your car may have a bad fan motor or some other problem in the system. If the fan is running when you change the fuse, you may not be out of the woods yet.
When a motor gets old and tired, it will draw more current through the wires than a new motor. It can still draw enough current to blow the fuse after it has been running for a while. In this case, the engine needs to be replaced.
Part 2 of 4: Accessing the Switch
Necessary materials
- hex keys
- Set of heads for deep wells
- inspection mirror
- led torch
- Tool for plastic panels
- Open end wrench (10 or 13 mm)
- Screwdrivers in different sizes and styles
Step 1: Disconnect the battery. Put on safety goggles and disconnect the battery from the negative cable.
If the system is energized, a metal tool in the wrong place can cause sparks and possible damage to your vehicle's electrical system.
- FunctionsA: If your car has a tamper-resistant radio, make sure you write down the radio code somewhere so you can activate it when you reconnect the power.
Step 2: Remove the handle. Replacing the fan switch begins by removing the handle.
In most cases, the handle is simply removed, but sometimes it is a little more difficult. Carefully inspect the handle from all sides, using an inspection mirror to look under it.
If there are holes in the handle, either unscrew the hex head set screw or press the push pin to remove the handle from the shaft.
Step 3: Remove the clasp. Remove the nut that secures the switch to the dash using an appropriately sized deep socket.
You should be able to push the switch inside the dash and pull it out where you can handle it.
Step 4: Access the Switch. Accessing the switch from behind can be very tricky.
The older your car, the easier this job will be. In most cases, the switch is accessed from the back of the dashboard and can only be reached by removing a few trim pieces.
Cardboard panels, held in place with plastic pins or screws, cover the bottom of the dash and are easy to remove. Switches located on the center console can often be accessed by removing individual panels on the side of the console.
Carefully inspect the plastic plugs covering the screws holding the trim panels. If you need to pry off a corner of something to see how it comes off, do it without damaging the panel with a plastic wedge trim tool.
On some vehicles, you can pull the radio and other accessories right out of the front of the console and leave a hole big enough to climb in and pull out the heater switch. Once you've made enough room, whether it's from the bottom or the front, the wiring harness to the switch should be long enough to pull the switch out while it's still plugged in.
Part 3 of 4: Replacing the Switch
Necessary materials
- needle nose pliers
Step 1: Replace the Switch. At this point, you should have the switch in position so that it can be easily turned off.
Be careful, there are usually locking tabs on the connector that need to be squeezed before it releases and disconnects. Plastic connectors are fragile and break easily.
Now you can plug in the replacement switch and test it out before putting everything back together. While there are no exposed wires, reconnect the battery cable and try starting the heater fan to see if other diagnostic work needs to be done.
If everything is in order, disconnect the battery again, slide the switch back through the hole and secure it with a nut. Reassemble everything back as it was and reprogram the code into the radio if necessary.
Part 4 of 4: Replacing the Heater Fan Relay
Necessary materials
- Owner's Manual or Repair Manual
If you checked the fuse panel and the fan motor does not run at all or only runs at lower speeds, the fan motor relay may be faulty.
Relays are used to transfer electrical loads that are too large for conventional switches. In some cases, the relay may only be connected to a high speed circuit. In this case, the fan will run at lower speeds, but will not work when switched to high. This can also apply to fully automatic systems.
Step 1: Find the Relay. The manual may refer to a fan relay, AC relay, or cooling fan relay.
If it says fan relay, you are golden; if it says ac relay you can get what you want. If the cooling fan relay is written there, then we are talking about a relay that controls the radiator fans. Some cars have something called a power relay or "dump" relay. These relays power the fan as well as some other accessories.
Due to some translation issues, some Audi manuals refer to this part as the "comfort" relay. The only way to know for sure is to read a wiring diagram to see if the relay powers the part you are trying to fix. Once you have decided which relay you need, you can use the manual to find its location on the vehicle.
Step 2: Purchase a Relay. With the key off, remove the relay from its socket.
It's best to have it handy when you call the parts department. The relay has identification numbers to help your parts technician find the right replacement. Do not attempt to install anything other than an exact replacement.
Many of these relays are very similar to each other, but internally they are completely different and installing the wrong relay can damage your car's electrical system. Some of these relays are quite inexpensive, so it's not that risky to try one of them.
Step 3: Replace the relay. With the key still in the off position, reinsert the relay into the socket.
Turn on the key and try the fan. Some relays may not activate until the car is started and have a built in delay so you may need to start the engine and wait a few seconds to make sure your repair is successful.
Depending on what you drive, this job can be easy or a nightmare. If you don't want to take a crash course in electronics to do diagnostics, or just don't want to spend a lot of time lying upside down under the dashboard looking for the right parts, contact one of AvtoTachki's certified technicians. replace the fan motor switch for you.
