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So your rear defroster don't work. This write up will help you diagnose the problem, and fix it.
Note to all. The pictures were taking from an online manual for a 1988 Honda CRX. The information is from a 91 Honda CRX Si. Some things are different but mostly the same.
Lets start out with the easy stuff. First check you fuses. There are two that power the rear defogger. One is in the fuse box under the dash(10A) and one is in the main fuse box under the hood(20A). If blown, replace.
Now for the more difficult stuff. Tools that are needed are a multi-meter, some jumper wires and a wiring diagram (included in this write up). Its also a good Idea to have extra fuses, just in case.
Switch Testing
The easiest way to see if you switch is working is to see if the light comes on when pressed. But, the switch light could just be old (it is 15+ years old) and blown out. To test, remove cluster cover for best access to the wires and switch. First, check to see if power is going to the switch. Take the multi-meter and set it to volts. Find a good ground and place the black lead on the ground. Take the red lead, and press it into the hole on the back of the connector where the black and yellow wire goes in. It should read a voltage. If not, check fuse again to make sure you did not blow it. If that's not the problem, you have a open some where on that wire. Trace the wire and replace bad section. Don't quote me on this part but Switches from 88 and 89 are different from the 90 and 91 switches in that the 88 and 89 don't have a time dial (not expert word). The 90 and 91 switches have a dial that turns and after about 15 minutes, turns the switch off. The 88 and 89 don't seem to have this. Once again, don't quote me on that part. To test an 88 and 89 switch, check continuity between pins A, B, and C (when switch is on) and then check D and E. If no continuity, replace switch.
Testing the Relay
This is, for the most part simple. Remove the relay from the fuse box.
Looking at the relay you'll see four pins. A, B, C, D Some are labeled while others are not. A and B is the switch side of the relay where C and D is your control side. Place jumper wires on C and D and test for continuity on the A B side. If there's continuity when there's power going through the control side on the switch side and there isn't when you disconnect the power, your relay is good. If not, replace with new one.
Next, check you see if you have power going to the relay. Once again, find a good ground and place the black lead of the multi-meter on it. Then, take the red lead and place it in to where the A pin would be(yellow and green wire). You should read close to 12 volts.
Rear Window Defogger
First things first, check to see if power is going to the elements. (Note: The ignition switch and defogger switch need to be on for these step.) Find a good ground in the rear, placing the black lead of the multi-meter on it, and place the red lead on the drivers side (positive side) connector. You should have close to 12 volts. If not, trace wire back to find open and replace bad section. Next, check the ground side continuity. Place one side of the leads of the meter on a body ground and the other lead on the passenger side (negative side) of the elements. If no continuity, trace the negative wire and replace bad section. For testing the defogger wires, us the multi-meter to check voltage from the middle of the wire to the negative side connector. The meter should read 6 volts. Check the rest of the defogger wires the same way. If there's no voltage, that wire is bad on the power side. If there's 12 volts, that wire is bad on the negative side. To fix a bad wire, First clean off around the bad area, and then masking area the area. Use a silver conductive paint and apply one heavy coat that extends about 1/8 of an inch on either sides of the break. Check to make sure you fix works after allowing to dry with method above.
That should be everything with the rear defoggers. Hope this helps the many people out there with problems with there defogger.
Tom
Note to all. The pictures were taking from an online manual for a 1988 Honda CRX. The information is from a 91 Honda CRX Si. Some things are different but mostly the same.
Lets start out with the easy stuff. First check you fuses. There are two that power the rear defogger. One is in the fuse box under the dash(10A) and one is in the main fuse box under the hood(20A). If blown, replace.
Now for the more difficult stuff. Tools that are needed are a multi-meter, some jumper wires and a wiring diagram (included in this write up). Its also a good Idea to have extra fuses, just in case.
Switch Testing
The easiest way to see if you switch is working is to see if the light comes on when pressed. But, the switch light could just be old (it is 15+ years old) and blown out. To test, remove cluster cover for best access to the wires and switch. First, check to see if power is going to the switch. Take the multi-meter and set it to volts. Find a good ground and place the black lead on the ground. Take the red lead, and press it into the hole on the back of the connector where the black and yellow wire goes in. It should read a voltage. If not, check fuse again to make sure you did not blow it. If that's not the problem, you have a open some where on that wire. Trace the wire and replace bad section. Don't quote me on this part but Switches from 88 and 89 are different from the 90 and 91 switches in that the 88 and 89 don't have a time dial (not expert word). The 90 and 91 switches have a dial that turns and after about 15 minutes, turns the switch off. The 88 and 89 don't seem to have this. Once again, don't quote me on that part. To test an 88 and 89 switch, check continuity between pins A, B, and C (when switch is on) and then check D and E. If no continuity, replace switch.
Testing the Relay
This is, for the most part simple. Remove the relay from the fuse box.
Looking at the relay you'll see four pins. A, B, C, D Some are labeled while others are not. A and B is the switch side of the relay where C and D is your control side. Place jumper wires on C and D and test for continuity on the A B side. If there's continuity when there's power going through the control side on the switch side and there isn't when you disconnect the power, your relay is good. If not, replace with new one.
Next, check you see if you have power going to the relay. Once again, find a good ground and place the black lead of the multi-meter on it. Then, take the red lead and place it in to where the A pin would be(yellow and green wire). You should read close to 12 volts.
Rear Window Defogger
First things first, check to see if power is going to the elements. (Note: The ignition switch and defogger switch need to be on for these step.) Find a good ground in the rear, placing the black lead of the multi-meter on it, and place the red lead on the drivers side (positive side) connector. You should have close to 12 volts. If not, trace wire back to find open and replace bad section. Next, check the ground side continuity. Place one side of the leads of the meter on a body ground and the other lead on the passenger side (negative side) of the elements. If no continuity, trace the negative wire and replace bad section. For testing the defogger wires, us the multi-meter to check voltage from the middle of the wire to the negative side connector. The meter should read 6 volts. Check the rest of the defogger wires the same way. If there's no voltage, that wire is bad on the power side. If there's 12 volts, that wire is bad on the negative side. To fix a bad wire, First clean off around the bad area, and then masking area the area. Use a silver conductive paint and apply one heavy coat that extends about 1/8 of an inch on either sides of the break. Check to make sure you fix works after allowing to dry with method above.
That should be everything with the rear defoggers. Hope this helps the many people out there with problems with there defogger.
Tom
