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4-way flasher lights on the 720


millican

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When one turns on the 4-way emergency flashers in a 720, which lamps are supposed the flash: the ones that come on with the parking lights or the ones for the turn signals?

I did find two flashers under the steering column, but both the turn signals and 4-ways seem to make the same one click. However, the turn signals do not work. There is a single, faint click, and only 1 to 6V at the socket. The 4-ways work fine, but it's the lamps that come on for the parking lights. Fuses and bulbs are fine. It just occurred to me that I should try checking the trailer light harness with the little plug-in checker. I'm not sure people would know what I'm doing if I started signaling with my arm out the window.

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FIRST

Turn the ignition and the turn signal on. Now move the 4 way flasher gently towards on. When the turn signal starts flashing, stop. Problem solved. The 720 4 way switch is known for traveling too far when returned to the OFF position. Just move it slightly toward ON.

 

 

 

Four way and signal flashers use the same bulbs filaments. Some front and rear running (or parking) lamps use a single bulb with two filaments in it. The brighter lamp is the signal/4 way and the dimmer is the running lamp.

 

 

Both the 4 way and the turn signal flashers are powered by two different fuses. The 4 way from the 4th fuse over from the far left hand side and the turn from the 12th fuse over from the fr left hand side. Check these fuses for 12 volts. Do NOT accept that they are good just by looking at them or you can swap another 15amp fuse in to see if anything changes.

 

NOTE:

The stock signal flashers are load dependent and flash speed is set by how many bulbs are drawing power through the flasher unite. A blown bulb filament can cause the flasher to work very slowly or not at all and the turn signal indicator in the dash will light and stay lit.  A trailer, with added lamps can cause the flasher to work ridiculously fast. To check the bulbs are working set the 4 way to ON and get out and make sure all bulbs flash.

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Thanks. I should have mentioned that I've slid and jiggled the 4-way switch quite a bit. There is also a lot of corrosion in the wiring. I've been just replacing things. I'm also suspecting the adapter for connecting the 4-wire trailer lights to a 5-wired system. The fuses were checked with a multi-meter. Knowing that the wrong lights are flashing helps. I'll work on it some more tomorrow, starting with removing the trailer light adapter. Happy New Year all!

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I couldn't troubleshoot this with the trailer light harness adapter attached. Once it was removed, it was easy to find that there is 12V going to the turn signal sockets with the the flasher, and that the socket wasn't getting a ground. It turned out to be inside the socket where the ground connects to the spring. It was corroded and getting a bad connection. The same was on both sockets, but the sockets for the tail/brake bulbs were fine. The wire on the turn signal sockets was just wrapped around the spring. I got the corrosion off  the copper wrap of the ground with some flux (acid) and soldered it in place to the spring. This worked on one side, so it was repeated on the other. Now everything works again. I'll re-connect the trailer harness some other time. Thanks guys!

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