2nd Gen Non-Engine/Transmission Question for the Electronic Gurus

[chucksram]

If replacing the bulbs in the rear of our trucks with LED's is not putting enough load on the system for the flasher to work properly. Why couldn't a relay on the circuit be used? Would this be enough of a load for the flasher to work properly? Use any relay on each light and run the wire from the switch to the coil and run the switched terminal to the LEDs.

Just got thinking about this tonight while driving home.

Thanks

Chuck

 

[Evan A. Beck]

No, a relay is not enough of a load to slow the circuit down. You need to add some sort of resistor in the circuit. A typical relay only draws a couple watts, which is not enough of a load.

 

[Gary - K7GLD]

It's my understanding that in past years, there were 2 types of flashers - one most commonly used, was the type that operated on and depended upon a known fixed resistance load of the various bulbs connected - that was why when a bulb failed, often the flasher stopped working.



The other type is one that essentially provided its own "load" as far as the flasher function was concerned, and was not at all dependent upon the number of bulbs connected - those were/are the ones commonly used with RV's, trailers and such, with varying numbers/types of lights to be operated by the flasher...



As far as I know, the latter type of flasher shouldn't care in the least what load (within the current carrying capabilities of its internal contacts) is placed upon it - it should function the same lightly, or heavily loaded...

 

[ronco]

Gary is referring to a heavy duty flasher. It has the ability to flash at a given rate, no matter what the electrical load is. I should flash the same rate with 1 or 10 bulbs in the turn or emergency circuit.



Ronco

 

[chucksram]

Evan.

Would a resistor in the groung side of the relay work?

Also, would a resistor wired in parrallel work?

Chuck

 

[Big White Beast]

Chuck.........

Thay make relay's with various coil impedances. This may in fact solve the problem but it seems way too extreme for the problem.



A resistor in series with the LED lights should work fine to stop the fast blinking but these also run the brake lights. I haven't had any experience with the LED lights so I'm not sure how it would effect it. Most LED's run on a set vlotage and if you excede it or drop below you will cut their life span short.



I would opt for the heavy duty flasher and be done with it. Brake lights and signals are too important to be messing with IMHO.



Garrett

 

[chucksram]

The only problem with the flasher idea is our trucks flashers have an ic chip in them. It would require some rewiring for a heavy duty flasher to work. If anyone has done this please let me know.

Thanks

Chuck

 

[Shelby Griggs]

I am not an electronics expert, but have some experience with this. I have had LED lights on my flatbed since new. There is no such thing as a heavy duty flasher for our trucks (newer than 1999??). The newer trucks use a 5 terminal flasher with an IC chip that runs a relay to actually do the making and breaking.



I tried the resistor for a while, but that defeats of the main benefits of the LEDS, a low current draw. You will need a fairly heavy resistor (ceramic) as there is a bunch of heat generated.



After searching for months, I finally located an after market replacement flasher, which is probably built by the same company who builds the OEM units, as it looked identical. I then had a fellow TDR member who is an electrical engineer reverse engineer the circuit. The bottom line is that I can adjust the flash rate to whatever I want by tweaking a potentiometer on the flasher. The downside is that my emergency flashers are inversely proportional to the turn signals. So far I can't have my cake and eat it too. We haven't done any more R&D since mid summer, but we had thought of perfecting what we had and offering modified flashers to the marketplace.



This is the best solution I have seen, until someone makes a non-load sensing circuit flasher for our trucks.



Shelby

 

[95REDRAM]

These new trucks, they seem to make changes on them just for the sake of change. My 95 has the old two terminal style flasher that has been around for how many years? I'd say at least half a century. Oh well, enough complaining.



I built a flasher assembly a couple of years ago that I think will do what you want for the newer trucks. One thing I'm not sure of though. Shelby said that the solid state flasher on the new trucks is controlling a relay. If that is the case then it would seem to me you could put any type of lamp on the circuit and it would work just fine as the flasher would only see the constant load of the relay coil. Can someone confirm this? I don't have a wiring diagram for a new truck to check this out.



Anyway, what I built is essentially a solid state flasher controlling a relay. I remember the flasher is manufactured by Littlefuse but have no idea what the part number is. I came across the flasher by chance while just looking over the display racks at PepBoys. The cover of the flasher is clear plastic and you can see the parts inside. I realized that it is a basic RC timing circuit that operates the flasher and thought to myself, I'll bet that would be adjustable enough to work with the load of the relay coil. It did and what I eventually built is a unit that can handle the load of the running lights on my truck with or without the trailer attached and will flash them as a thank you with the push of a button. It works whether I have the lights turned on or off. Push one button, runniing lights blink until the button is pushed again.



I think the same basic design would work for the turn signals and 4-way flashers on the new trucks. I'd need the wiring diagram to figure out the details of exactly how and where to install the relay(s). I figure it would probably take two relays, one for the left and one for right with both being activated for using the 4-ways.

 

[Gary - K7GLD]

I don't understand why, if the new style setup flasher is merely the controller for the relay that does the actual make/break for power to the bulbs, there is even a NEED for a special flasher - unless part of the circuitry feeds load info back to the flasher in case of an unusual current draw situation? IF not, doesn't seem to me the flasher would have a clue as to what actual load was being switched...

 

[Shelby Griggs]

I don't understand it all either, but there is definitely a coil that makes and breaks contact within the case of the new flashers. It is also definitely load sensitive, and is designed to flash at double rate in case of a bulb failure, so I know it senses load somehow. The case comes apart pretty easy on your OEM flasher, if anybody wants to take a look.



Shelby

 

[fest3er]

Originally posted by Shelby Griggs

I don't understand it all either, but there is definitely a coil that makes and breaks contact within the case of the new flashers. It is also definitely load sensitive, and is designed to flash at double rate in case of a bulb failure, so I know it senses load somehow. The case comes apart pretty easy on your OEM flasher, if anybody wants to take a look.



Shelby

Hmmm. This might explain why my turn signal has, on occasion, gone to double-time. I guess I need to pull all the blubs and check the contact surfaces.



Fest3er

 

[15w40]

The new style, electronic flasher, used in our Rams is a solid state circuit and relay to switch the bulb on and off. The design also samples the current to the bulb and will flash at a faster rate with a bulb burned out. This duplicates the older bi-metallic flashers with a heating element to turn on and off the bulb.



To modify the new, electronic flasher, all that is needed is to change the value of the current sampling resistor. This resistor is usually only a printed circuit trace. I have not looked at the Ram flasher relay, but usually the trace is shaped like an “S”. Cutting this trace and soldering a piece of thin gauge (20 AWG?) about 2” long from each side of the cut trace will increase the resistor value and stop the fast flash.



I have not experimented with this on my truck. The wire gauge and length may have to be experimented with to get the right resistor value.



If anyone works this out, report back with what works. I am just now thinking about using the LED turn and stop lamps.

 

[CRegal]

Ok, here is what works for me, 5 ohm resistor w/ a 25 watt ratting in parallel with the led. Very simple to hook up & doest lower the voltage just the current draw. No more fast flashy & it really dozen't heat up that much. I tested it with the turn signal on for like 15 minutes & the temp was fine.



You will need two of them, one for each led. It DOES NOT affect how bright the led is, remember parallel, just like your Christmas lites.

 

[Eric Kahn]

If you have the old style flasher, you can go to most truck stops and buy an electronic flasher that replaces it that does not care how many or what type of lights are in the truck, they cost about $14