Need wiring diagram for flasher relay/Hazard - VW Forum :: Volkswagen Forum
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post #1 of 3 (permalink) Old 09-09-2010, 02:17 PM Thread Starter
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Need wiring diagram for flasher relay/Hazard


Can someone please help. I need this diagram to repair this circuit which is fried beyond repair. I tested it today and there are problems inside the fuse panel. Indicator wires going to the steering column are showing ground which is a problem I followed them and they are ok but shorted out somewhere inside the fuse panel. I will have to create a totally new circuit from new wires which is the easiest thing to do.

The problem is, I dont have a Bently manual here because I am currently in Lebanon, Middle East. Can someone please take a picture of that page for me?

Or if someone knows of something online...

I have only managed to find online this diagram which looks pretty close to the circuit but I am not 100% sure about it and would like to confirm this.The system uses a 3 terminal relay (#21) which also got fried and needs to be replaced.

Thanks guys.
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Last edited by rar; 09-09-2010 at 02:21 PM.
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post #2 of 3 (permalink) Old 09-13-2010, 02:50 PM Thread Starter
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Hi again,

I have finally solved the problem and wanted to share with you all some feedback, just in case it may help someone someday when they encounter the same problem. That’s what forums are about…

It took a while to solve it. Two full days of diagnosing, tearing apart and putting it all back together again. I started off by removing the panels under the dash board, the upper panel and cluster, so that I have better access to the wiring. I got a new relay and a used hazard switch, because I suspected them and thought that I would like to have spare ones anyway, even if they didn’t turn out to be damaged. I bought a good multimeter and tested the relay. It seemed to be working fine according to the circuit diagram I attached in the last thread entry for a 3 terminal relay # 21. The hazard was ok as well.

First thing, I checked the fuses and they were all ok. Then I checked the wires that start from the fuse panel and go to all four corners of the car to the indicator lights. The easiest way to do this is to remove the screws that secure the fuse panel and swing it off. I inspected the wiring to see if anything looked burned/melted. Then I pulled off the 5 harnesses in the back. They are coloured so make a note of the order from left to right so that you can plug them in correctly later.

Then I disconnected the battery and got a long wire prepared to do some testing. I also recommend that you buy some short testing wires that are coloured and have alligator clips on both sides. These really come in handy while using the multimeter. You can find these at the electronics supplies stores. I continued to remove the indicator covers and the bulbs to commence testing.

Next, I tested to see if there is a short in each individual indicator circuit (LF, LR, RF, RR). I did this by connecting the + wire of the multi to the long wire and then to the battery’s +. With the car’s ground terminal connected to the battery, I touched the negative of the multi to the positive prong where the bulb mounts. If it reads 11-12.7 or so volts, that means that there is a short in the wire or fuse panel. It shouldn’t read anything! I did this for all four indicators to insure that there wasn’t any shorts.

Next I wanted to locate all four wires on the harnesses that connect to the fuse panel. Only do this if there isn’t any shorts in the wires! (If there is a short you must inspect the wires and tear everything apart) I ran the long wire to the positive prong where the bulb mounts and connected it directly to the positive of the battery (disconnect the battery from the car again). While 12v is running through that circuit, I used the multi (with the black connected to the negative of the battery) to test each little connector hole (about 20 in total) on each of the 5 harnesses. When I found the connector that has the 12 volts, I noted the number of it and the colour of the harness. I continued until I found all 4 indicator wires.

On a 1978 Golf MK1 GTI the results were:
LR = Yellow #19
RR = Yellow #16
LF = Off-White #6
RF = Bright White #18

All MK1s may be the same or differ. I am not sure. You should get from 11-12.6v in each circuit. If the voltage is (much) lower, compare it to the voltage of the battery (test it separately). If lower, then the wire is damaged, corroded etc. You can also test the impendence (ohms) of each wire circuit which will tell you the condition of the wires. It should be as close to 0 as possible. 0.1 or 0.2 is acceptable but not much higher than that.

Since I found all four, this was good news. If they are all not found, this means that a wire must be damaged and repaired or replace completely depending on it’s condition when you cut and inspect it. The wires are all running on the driver’s side.

I previously cleaned all of the harnesses and pins with WD-40 and a toothbrush. Make sure you do this if you find that they are corroded. After this, I connected the new relay and Hazard light, and tried it. Still, the damn thing didn’t work so the problem is not from those.

I decided that since it was an old car, and it has been played around with by people and there were lots of loose or untapped connections, I decided to check all the wires in the car. This doesn’t have to be done if the previous test succeeded. I ripped apart the wires and inspected them. All were still OEM and untouched and in good condition.

I inspected all of the wires from the fuse panel to the hazard switch, lights switch, cluster, indicator switch on steering column etc. All were good. So this leaves only one possible reason for it not to work…the fuse panel! When I first got the car 9 months ago, it worked on and off and then stopped completely.

I tested the place where the relay plugs in. It has 4 slots but the relay only has 3 terminals. The slots are located top, bottom and left. According to the relay diagram, the top one should be ground, the bottom 12v ignition, and the left one is connected to both the indicator switch on the steering column and hazard switch. The top (31) one was giving ground as it should. The left(49a) one was connected ok but the bottom one(49) wasn’t giving 12v ignition and was dead. I rechecked all the fuses and made sure they were tightly mounted. Still didn’t work.

I tried to find a replacement for the fuse panel but there wasn’t one available in my area. So, I had to cancel the circuit of the relay on the panel and wire-up a separate one. I attached a new harness for the relay and soldered all connections to ground, 12v and to the switch and hazard. You must find a wire that goes from the hazard switch to the fuse panel. It is coloured black, with a thin green and white line. Make sure it is the one with the multi set on ohms before you cut.

After I connected the relay and tested it. It worked! Both the indicators and the hazard worked fine after that. This was the best that I could do in my situation (couldn’t find a replacement fuse panel).

So there must have been something wrong inside the fuse panel. This usually gets damaged by mostly water leaking from the windshield seal over the years.

I hope that this information helps someone one day if they run into a similar situation. It took some research and a lot of problem solving, but in the end, I was able to understand how this type of relay works, and how the circuit is wired.

Basically how it works is that the relay is the heart of the whole circuit. It has ground, 12v ignition power and is connected to the rest of the circuit through the 49a terminal. When the power are ground are provided (49 + 31), the 49a becomes live also with 12v but the relay doesn’t start ticking until there is a load on that terminal (bulbs are connected). I tried connecting a bulb and it began to tick when it sensed a load. This 49a connects directly to the indicator switch handle and the hazard. When you pull down or up the indicator handle, you are completing a circuit which ultimately connects the 49a to the left or right lights on the car, thus triggering the relay to tick on and off. The hazard is also connect to the circuit but has a full time 12v on it so that it works without the ignition key, unlike the indicator handle. The hazard connects all 4 bulbs instead of 2 and triggers the relay . Also there is a connection from the 49a to the little LED on the instrument cluster. This is wired to the fuse panel. You will have to find this and connect it.
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post #3 of 3 (permalink) Old 09-19-2010, 04:10 PM
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I just saw this post. Great explanation. I could of never explained it that well. Also geat detective work. Good thing is that is how VW did it from 73 thru the MK3s.
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