Turn signal switch-WTH

[Goblinking]

Can anyone explain how the hell you test a turn signal switch on a 79 d150?
I had all lights working except the drivers side stop light,now i have no indicators at all,but that single brake light still works.
Pull the hazard switch,all indicators flash apart from drivers rear,but indicate right at the same time and the bulb flashes ok.
I have cleaned the earths,obviously the bulbs are ok.I can't find a switch in stock anywhere at the moment except this one from summit

https://www.summitracing.com/parts/oer-md2094

It says it wont fit my truck,but i swear its exactly the same as the one thats on there.

[mustangbooks]

That's an 8-wire switch, is that what you have? There's an 11-wire version which seems to fit more of the later models "for full size models equipped with cornering lamps":

https://www.oerparts.com/product/md2085.html

[Goblinking]

Hello,yes,I deffo have the 8 wire one

[MilesnMiles]

If your hazards are working the turn signals it means power is getting out of the switch. Have you actually tested the bulb holders to see if they are actually earthed? They earth through the bulb holder socket itself and it’s essential that they earth.
I have a problem with one of my turn signals not grounding ( so not working). I did a lot of searching and I’m cutting and pasting an article which helped me most:
‘ The wiring for the side markers "looks" complicated, but it's simple. THERE IS NO ground for the side marker lamps, here is how they work

One side of the side marker is connected to the park light circuit

The other side of the lamp is connected to the turn signal.

With park lamps on, turn signals off, the side marker gets power from the park circuit, and "goes to ground" through the unpowered signal lamp filament, so the side marker lights up, a much smaller bulb wattage than the park or signal lamp

With the park / headlights ON, and you turn on the turn signal, the side marker LIGHTS when the signal lamp is OUT, again grounding through the filament of the unlit signal bulb. But with the signal lamp LIT, now we have power at both sides of the marker lamp connection, so the marker goes OUT while the signal lamp is LIT

Now, with the park lamps OFF (daytime) we have the OPPOSITE condition. When you turn on the turn signal, and the signal lamp is LIT, power is applied from the signal circuit to one side of the marker lamp, and it "gets ground" through the now UNLIT filament of the park lamps, and so the marker lamp lights
=============================================================

Now, just what have you checked? Remove the park/ signal lamps from their sockets, and CAREFULLY probe the socket with a test lamp. Tape up the lamp probe to help prevent shorting, and make sure you have a good ground at the clip of the test lamp. If necessary, make an extension clip lead up so you can ground the test lamp back at the battery or block.

If you don't see power at the socket(s) go back to the bulkhead.

What have you done to "check the ground?"

Turn on the park lamps, and if you have power at the socket, install the bulb, wiggle it around. Now take your grounded test lamp, and "stab" the probe right at the side of the socket. If the test lamp lights, the socket is NOT grounded.

This is a SIMPLE circuit. You have three wires to run the entire show.

The park light power comes from the headlight switch, runs through the bulkhead, and "y's" off to each park light bulb

The front signal power comes out of the column connector from the signal switch, "y's" off to the instrument panel indicators for left and right, and goes through the bulkhead, through the lighting harness, and up front to the connectors for the sockets.’

[Blue]

I can tell you from experience the quality of replacement switches is really poor. I had one that kept jamming, another that was so stiff I thought it would break everytime I used it and my current one which I have to waggle about to turn the indicators off. None of them would self cancel. I have read in several places Danial Stern lighting make a decent one http://www.danielsternlighting.com/prod ... s.html#Buy so I’ll try that next.

[Goblinking]

Hello fellas and thanks for answering.I ordered that switch from summit and it arrived today,fitted it and everything is working mint.It doesnt have the "feel of quality" of the original switch,but it seems to be working fine.
Miles,thank you for explaining how the circuits work,it was actually very interesting,i was racking me brains over it for ages and that cleared up things for me.

[MilesnMiles]

Glad you got it sorted, nothing like an easy fix

[Steve]

Just wanted to echo what Blue said, Daniel Stern all the way, great quality. Not cheap but the best.

[Dave999]

if the switch part works but the self cancelling cam has bits snapped off
buying a new cam is often a better bet than a whole new switch
US and Aussie Ebay https://vansauto.com/product/turn-signa ... -b-c-body/
and similar

self cancel only works if your steering wheel boss has a pressed on spring steel ring with its end bent down to ping the cancel cam
i have 3 crush tubes and two of them have this bit missing
if yours never had one you'd be unlikley to spot anything wrong as the horn still works even if that copper conact is missing


Dave