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70's chevy c20/rv taillights


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losboricua 
Copper - Posts: 135
Copper spacespace
Joined: November 09, 2003
Location: Ohio, United States
Posted: September 02, 2013 at 8:48 PM / IP Logged  
So my buddies and I bought an RV last year to use for tailgating. Last year all we did was paint the outside because football season already started. This year we gutted the inside because of water and poor remodel job before. I have been replacing a lot of the wiring because the hillbillies that owned the RV before used 20ga speaker wires in a lot of places. Lot of ground issues and water damage cables. I have ran at least 250+' of 16ga cable and new battery cables.
I just got done mounting and running the new taillights cable to the factory hardness. My problem is that my new LED taillights have 5 wires each(turn signal, stop, running light, reverse and ground). the factory hardness only has 4 total for both lights(left turn signal @ ~8 volts + Brake @ 12 volt, right turn signal @ ~8 volts + Brake @ 12 volt, running lights and reverse). I need to separate the turn signal out of the stop light. How can I do this? I have seen some boxes online that allow you to go from 5 wires to 4 wires for a trailer. Can I use the same box the other way around(aka, it doesn't have diodes inside?). Or is their a relay that and diode that I can use? or can I cut the stop light from going to the wiring hardness in the fuse box and then run a separate wire for the stop light?
Thanks in advance, i just have not been able to find a factory wiring diagram for the Chevy c20/rv.
2015 Hyundai Genesis Ultimate Black on Black
Tinted Windows, Fogs, Roof Spoiler, ARK Springs, Ruff R1 20's Staggered
i am an idiot 
Platinum - Posts: 13,668
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: September 02, 2013 at 10:42 PM / IP Logged  
On the stock wiring, there are 4 wires left and 4 wires right? Is a ground in the 4 wires?
i am an idiot 
Platinum - Posts: 13,668
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: September 02, 2013 at 10:45 PM / IP Logged  
Connect both the new running lamp and turn signal wires to the appropriate wire from the vehicle.   Does that help?
oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: September 02, 2013 at 11:29 PM / IP Logged  
It sounds like the original has a combined stop/flasher.
If so, the most straight forward solution is to connect the stop lights direct to the stop switch output, and the flashers each to the appropriate side of the flasher switch output but also insert the flasher can into the input side of the flasher switch. [The flasher can needs to be LED compatible if it wasn't before.]
If you have any other lights that disconnect when flashing (eg, front or side clearance combined with flasher) then the above won't work on its own...
Reversing the connections of specialised circuits to "invert" their function won't work.
losboricua 
Copper - Posts: 135
Copper spacespace
Joined: November 09, 2003
Location: Ohio, United States
Posted: September 03, 2013 at 7:32 AM / IP Logged  
Ok, so just run a extra cable from the brake switch to the brake pedal. If I disconnect the factory brake cable that will prevent the turn signals from turning on when the brake is applied and it would not mess anything else up because the RV is so old that it doesn't need brake signal for anything else right? Also for the turn signals, I do not have LED flashers but I have load resistors, that should work right?
Thanks
Carlos
2015 Hyundai Genesis Ultimate Black on Black
Tinted Windows, Fogs, Roof Spoiler, ARK Springs, Ruff R1 20's Staggered
oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: September 03, 2013 at 9:54 AM / IP Logged  
Yeah - brake switch to dedicated brake lights should be ok. If you did have any other thing associated with the brakes, that should be off the brake switch as opposed to the brake light so shouldn't it/they be effected.
The flashers are more complex IF they were part of a combined brake/flasher light/bulb. (It's the same as older non-stateside vehicles that used combined reverse/flasher bulbs.)
Whereas a dedicated flasher bulb system has +12V thru the flasher-can which is then connected thru the left/right switch to the respective left/right flasher lights, shared flasher bulb systems (eg, flasher/stop or flasher/reverse) instead have +12V to the flasher switch which then switches L or R to L & R relays that disconnect the "other" signal (eg, brake) from the bulb and instead connect the can to that bulb. That requires a DPDT relay per side (else SPST and SPDT) but the flasher switch can do that instead of relays. (IE - DPST relays are used to convert single-pole SPDT (center off) flasher switches to combined bulbs systems, but some vehicles manufactured for combined bulb flashers may have that SPST + SPDT switching done by the flasher switch. Note that the SPST is required to connect the front flashers.)
The point is that for dedicated flasher systems, the flasher-can is BEFORE the flasher switch (ie, +12V thru the flasher-can to the input of the L/R flasher selector switch) whereas combined reverse or brake & flasher bulbs effectively have the can AFTER the switch (ie, +12V to the switch which then energises the L or R relay which connects the can to the front & rear bulbs). The "all in one" flasher switches do similar.
Simple eh?
Hence electrically speaking, the flasher-can has to be relocated to BEFORE the switch when converting to dedicated flasher bulbs/lights.
The upshot is that although the brake lights should work ok (with a simple requiring to the brake switch), don't be surprised if the flasher bulbs/LEDs aren't that simple.
I can say more about the use of load resistors for LED flashers, but I'll leave that for now (it's a multifaceted argument or situation depending on why LEDs were chosen, and in part about "expensive" load resistors etc...).
Load resistors will do the job, especially if they have already been purchased.
losboricua 
Copper - Posts: 135
Copper spacespace
Joined: November 09, 2003
Location: Ohio, United States
Posted: September 03, 2013 at 12:48 PM / IP Logged  
Oldspark,
Thanks for the input. I will be just Isolating the brake and I have some load resistors that someone gave me that is why I said that about them. As far as the flasher can, mine when the ignition is on one side is hot and then when I hit the flashers then the other side turns hot. is that how it suppose to work? I know typically it goes battery, flasher can, turn signal switch and bulbs. Isn't that basically how it is setup now then since the load side does not become active until the switch is on. Thank and sorry. I have just started to learn how flasher work.
Attach is a picture of my fuse block if that even helps.
Carlos
70's chevy c20/rv taillights -- posted image.
2015 Hyundai Genesis Ultimate Black on Black
Tinted Windows, Fogs, Roof Spoiler, ARK Springs, Ruff R1 20's Staggered
oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: September 03, 2013 at 6:57 PM / IP Logged  
Image file names have to be short - I think up to about 10 characters. Hence download, rename with plain characters, and upload.
And confirm that they appear by using the Preview Post button before submitting via the Post Reply. (There is no other warning that they won't appear.)
However I could view your image by viewing its dropbox link.
Yes you are right about typical flasher wiring (in old cars, and without combine flasher/stop etc bulbs).
It is +12V (IGN +12V) thru fuse to can and from can to the switch.
The switch then completes the circuit to the left or right bulbs.
The way traditional "thermal" flasher cans work is a resistive "wire" from its input to output. (Hence cans measure as +12V on their output even when not flashing.)
When the much lower resistance (ie, higher current) bulbs are attached, current flows through the wire which heats up an arm that closes the main contact, thereby connection the input +12V direct to the bulbs to light them.
Being then shorted out (or bypassed), the hot wire cools, the arm contracts and opens the main flasher contacts, thus extinguishing the bulbs, and the cycle starts over again.
Incidentally, the same technique is also used in older voltage regulators used for some dash instrumentation (eg, temperature & fuel gauges).
But as opposed to the voltage regulator versions (for gauges, NOT alternators etc), flasher cans are often designed for specific loads - ie, 2 x 21W plus a few extra 2W/3W bulbs. If a main (21W) bulb blows, the heating wire heats up slower which means the flasher cycles faster hence warning drivers of a blown bulb (something that many local drivers seem ignorant of! 70's chevy c20/rv taillights -- posted image. ).   
Hence why substituting LEDs (typically 1-2W if that - instead of ~21W) results in hyper-flashing.
One solution is to refit the original bulb(s) in parallel with the LED(s) - though maybe somewhere else (in trunks or under guards or anywhere after the switch) - but then sellers can't make money selling relatively expensive load resistors.
Whilst the latter may be amusing from a $money etc POV, I find it very amusing when the reason for fitting LEDs was to reduce the vehicle's electrical consumption - ie, it remains the same. Hence my main points about NOT using an appropriate flasher-can instead.
Newer flasher-cans are electronic. They sense the current thru a low-Ohm resistor (aka shunt) and then start a timer that flashes a relay.
Some of those can be modified for LEDs by changing the resistor that samples the voltage across the shunt. That resistor is specifically selected (to suit the circuit) so that normal "heavy" current (ie, 2 or more 21W bulbs) has a normal flash rate, but less than that results in a fast flash rate - hence imitating the warning behavior of traditional thermal flasher cans.
And then there are (electronic) flasher cans suited to LEDs.
Usually these are simple relay flasher circuits than handle any output current, and do not have any blown bulb or LED circuitry.
Blown LED sensing flasher are (or should be) available for bulb-less LED flasher, though these are usually expensive. But appropriate modification of a modifiable electronic flasher should achieve the same - at least for total loss of one of the main LED bulbs - assuming the dash indicator is also a LED (ie, not a bulb).
So there, a flasher-101 course as I understand them. And you got my objections to using load resistors (tho without mention if how hot they get...).
More than a simple answer, but since you seem interested in how they work etc...
davep. 
Gold - Posts: 641
Gold spacespace
Joined: May 27, 2011
Location: California, United States
Posted: October 03, 2013 at 10:50 PM / IP Logged  
losboricua wrote:
I need to separate the turn signal out of the stop light. How can I do this?
On a Chev C20 there is a long inline connector on the inboard side of the steering column for the turn signal switch. The number of wires vary by year and model, but basically there should be brn, blk, lt blu, dk blu, grn, yel, pur, and wht. Probably some others too, but that's enough to identify it correctly.
The white wire at this connector is the brake light input. Remove the body-side wire from the connector. Connect the new lights' brake input here. Leave the white wire going into the steering column disconnected.
If you don't disconnect the brake input to the turn sig switch, the rear turn sig bulbs will illuminate with brake.
That's all you have to do for the brake lights. I know nothing about making LED lights flash properly, but you've got that handled.

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