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Discussion Starter #1
Hi Everyone,

I have the weirdest problem. My reverse lights are not working and I can not figure out why. I tested the continuity on the reverse switch and that worked fine. I tested the cable that connects the reverse lights and thats showing 17w, I plugged the cable in and tested the plug where the light goes in and its showing 16w. I tested continuity on the light bulb and it looks fine, I even got some new bulbs rated at 16w, but still reverse lights are not working?

What could possibly be the issue. I'm stumped

Thanks,
Aleks
 

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Can you answer a few questions for me?

With the key in the on position, and car in reverse.

1. Do you have 12volts at your red/black wire at your back up light switch?

Switch Ignition off.

2. How many ohms are you reading between your red/yellow wire on the switch to red/yellow on ech reverse light socket?

3. How many ohms from the black wire on each socket to ground?

DJ
 

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Discussion Starter #3 (Edited)
Can you answer a few questions for me?

With the key in the on position, and car in reverse.

1. Do you have 12volts at your red/black wire at your back up light switch?

Switch Ignition off.

2. How many ohms are you reading between your red/yellow wire on the switch to red/yellow on ech reverse light socket?

3. How many ohms from the black wire on each socket to ground?

DJ
The wire at the backup switch is black and green and I forgot to actually test the voltage their, but as you will see from bellow it should be fine. I also didn't test to ground, I tested the wire itself one hole for the negative and the hole for the positive. I can test to ground if you think it will help?

I'm not sure if I can answer all of those as I didn't see all those wires.

So let me maybe explain the full procedure and what i tested.

I unplugged the connector that connects to the reverse switch on the gearbox. I then tested the reverse switch for continuity. When I put it in reverse, there was continuity, when i put it back in neutral there was no continuity.

I then connected the reverse switch back. I went to the boot. First i tested the wire that goes into the reverse light socket. With the car set in reverse it showed 17w. If i put the car back in neutral it shows nothing.

I then tested the socket with the cable plugged in. Again with the car in reverse it showed 16w this time, if I put the car in neutral it showed nothing.

I hope that helps.
 

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aleks001,

What kind of tester are you using?

I am not sure how your tester would come up with 17 watts with a circuit that is suppose to less than one ohm at the socket. Does it have a resistive internal load to simulate a light bulb?

P= I X R

So your tester read 17watts with no bulb installed, you shouldn't have a power reading if the connection is good. It takes approx. 10 ohms to get that reading. If so, then we do not have a full 12volts getting to the bulb.
If I am understanding this wrong, I apologize.
Can you tell me the voltage reading for the socket with the bulb out?

One pin should be battery voltage while the other pin should have less than one ohm to ground.

D.J.
 

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Discussion Starter #5
Sorry, I'm just learning to use the multimeter. Before when I was getting that reading, what I did was put one lead in one hole and the other lead in the other hole.

This time I tested it by grounding the black lead and this is what I got.

Out of one of the holes that connects to the lights ballast, it shoes 0.05, the other hole shows 0.21

I set the multimeter to DC and at knob to 20 so Im assuming thats 5 watts and 21 watts. Correct me if I'm wrong. When I took it out of reverse and left the key at pre-on position it showed 0.03 out of one of the holes.

So to clarify this is testing the cable that connects to the ballast that holds the bulb.

So what do these numbers mean.

Sorry for the lame explanations, I'm good with mechanics but SHOCKING :p with electrics :D
 

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Alright, now we're getting somewhere.

When the multimeter is set to DC, you should be reading volts.

So lets stick to volts at the socket of the light bulb itself. With the bulb out, the in the on position, and the car in reverse.

Black meter lead to ground and check both socket leads. One should get battery voltage, which should be around 12 volts.

The other should have zero volts. The one with zero volts can now be testing using the ohm's function of your meter. Black lead to a good ground and the red lead to the zero volt socket terminal should yield less than 1 ohm.

Let me know what those results are.

DJ
 
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Discussion Starter #7 (Edited)
Ok update ^^

The one with the power and the multimeter for DC set to 20 showed 0.16 and 0.18 but in general it was in that range.

I then set the resistance knob to 2k and it showed 0.065

Which means nothing to me :D but hopefully something to you :D

Thanks for your help so far :)

And this was all recorded with the ignition set to ON and gear put in reverse.

Also when i set the resistance to 200 instead of 2k it was about 4.75 if i recall correctly, so that is definetly not less then one ohm :S What does this mean :(
 

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OK,

Lets double check that your meter is working properly by testing your battery voltage. Set your meter to DC and range to 20.

Basically this means that you can measure 0 to 20 volts dc, which a car's electrical is based on 12, so this fine.

If your meter reads 12v, give or take a little, than your meter is good. Remeber to never use the resistance function where there is power. This can ruin your meter.

If you read no voltage at the light socket, then we do not have power. So now we head back. There is a 5Amp fuse for the back up lights, did you check that?

DJ
 

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Discussion Starter #9
OK,

Lets double check that your meter is working properly by testing your battery voltage. Set your meter to DC and range to 20.

Basically this means that you can measure 0 to 20 volts dc, which a car's electrical is based on 12, so this fine.

If your meter reads 12v, give or take a little, than your meter is good. Remeber to never use the resistance function where there is power. This can ruin your meter.

If you read no voltage at the light socket, then we do not have power. So now we head back. There is a 5Amp fuse for the back up lights, did you check that?

DJ
Meter is fine, i just bought it :p I tested the batter the other day and it showed 12.5v. I did check the fuse i swapped it around and with another 5Amp one and the lights still didn't work. Can i use the multimeter to check the fuse and how?

Also what did my resistance tell you?
 

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Well 4 ohms to ground is to much but, we need to get the 12 volts to your lights.

Black lead to your battery negative terminal. Red lead to test voltage.

The switch is fairly easy to get at, can you poke the two wires with the key on and the car in reverse?

If you get 12 volts on one wire and not the other, then the switch is not working. (Or you could unplug the sensor with the car in reverse and with the meter in 2K ohm's setting, measure across the two terminals. 0 ohms or close to it, is good.)

If you get no voltage, then we need check the connection closer to the ignition switch.

if you get 12 volts on both sides of the switch, then we need to check the wiring between thwe swicth and socket. there are two connections before the reverse lights.

I will scan the pic's of these connector locations if you need them.

DJ
 

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Discussion Starter #11
Well 4 ohms to ground is to much but, we need to get the 12 volts to your lights.

Black lead to your battery negative terminal. Red lead to test voltage.

The switch is fairly easy to get at, can you poke the two wires with the key on and the car in reverse?

If you get 12 volts on one wire and not the other, then the switch is not working. (Or you could unplug the sensor with the car in reverse and with the meter in 2K ohm's setting, measure across the two terminals. 0 ohms or close to it, is good.)

If you get no voltage, then we need check the connection closer to the ignition switch.

if you get 12 volts on both sides of the switch, then we need to check the wiring between thwe swicth and socket. there are two connections before the reverse lights.

I will scan the pic's of these connector locations if you need them.

DJ
I have a feeling that its the reverse switch on the gearbox that isn't working as it should. It has continuity but I think it might not be sending enough volts down. I will measure it when I get home tonight and let you know what it is. I will also measure the ohm between the two connecters that run of the switch.

Thanks,
Aleks
 

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Discussion Starter #12
Its the backup switch for sure. I got home put the car in reverse unplugged the connector from the switch.

Now the continuity doesn't even work on the switch. I could also not get a volt reading out of either part of the backup switch. I then tested the connector that connects to the switch and wouldn't you know it one pin shows 12.34 volts and the other pin 0. Perfect :D I Then did the resistance test on the backup switch. The ohm meter set to 2k it showed .143, I set the meter to 200 and it showed 143.34, that is a lot of resistance :p So I will be ordering a new back-up switch tomorrow :)

Thanks for all your help. If you think my diagnosis is wrong let me know because I can always cancel the switch if its not the problem, but I'm fairly certain now that it is.
 

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Discussion Starter #13
Ok, it was the back-up switch and just to let future people know who are thinking of changing it, gearbox oil will come out, so have your new switch close to you.

And thanks djburn for all your help :)
 

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Glad to hear that you got her fixed, good job.

DJ
 
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