I was wondering when you be throwing up a schematic. Now yer talkin'

So Sscully, the FET's are used as simple switches (that's how I've been using them for years).

I can see no load dependency, at least from those drawings - so I cannot understand why the flash rate would change. A FET (that's Field Effect Transister for y'all), in that configuration, is analogous to a mechanical contact. Either it's high (dang near infinite) impedance, or low.

EDIT - actually, rethinking this, I believe the load sensing is embedded within the SJB inline with the trace that supplies the load via the FET. The FET's themselves typically have approx 0.25 ohm (on) impedance; it would be trivial to calculate load via the voltage drop across that component when it is 'on'.

(For anyone interested, here's what a typical on looks like http://www.datasheetcatalog.org/data.../MTB16N25E.pdf )

This is intruiging. Thanks again for you help & info. You are a wonder

 

The FET is being sued as a switch for individual circuit protection, not the flashing for the turn signals.

They are installed on more than just the front turn signals, and rear stop / turn lamps.

The low beams on the headlamps have FETs installed ( don't quite get the usage there, they were individually fused to begin with ), but the high beams do not have a FET installed.



The cargo and puddle lamps have FETs installed ( got me, there is only a single FET with the fuse, on the puddle lamps, would make more sense to have a FET on each side with the single fuse like the turn signals do ).



In posts I try to make a point of just don't take what ever circuit you want to for mods, as if you have a problem with the circuit, the FET will shut off, and until the error is cleared, it will not turn back on ( clearing FET DTCs, is a serious problem with the install, not just additional load, and if bad enough the FET is shut off for good ).

The good part is, the fog lamps mod for the 09-10 that I posted the diagram for is a bit more involved ( when compared to previous MYs ), but there are no FETs installed on the fog lamps, so the mod should be a no brainer.
Requires 2 relays, and 2 add-a-fuses to make work.

 

Hmmm... why so complicated? The FET can be used for both.

And - (at least @ the granularity apparent in those schematics) I don't see any other mechamism that switches load power. The only thing inline with the bulb filaments is that FET - hot to FET (via fuse); load to ground. And the micro-controller driving the gate is the only other thing I see ...

It would seem to me that the fuse would provide the only protection needed (?)

Sorry - not familiar with the new MY's, or FET DTC's, so I'm just thinkin' out loud. I'll shut up now

 

Think about the rear turn / stop lamps. Something has to turn the circuit on for the function ( continually illuminated for the stop lamp, or flash at the rate for the turn signal ), and know which side to do it with.

The mirco control is what is turning the FET on and off for the function needed. The FET cannot make the flash, without the input from something else.

I think the reason for the FET is to be able to isolate the short to ground condition on part of a circuit, as well as it is being used as a relay of sort, so the mirco control function does not have to be a load capacity item ( as the MFS is in 97-08 MY, which causes problems at times ).

If the turn signals have a problem in a 97-08 MY truck, the 1 fuse for the turn signals is blown, leaving the isolation to a divide and conquer method ( 4 corners, plus dash and signal mirrors ).
With the FET, a short to ground, only shuts off the part that the problem is in, removing 87.5% of the circuit that is functioning from diagnoses.

The headlamps, I do not understand why part is FET and part is relay controlled. Seems like there is a plan for something else later, that this is setting it up for.

 

Yeah - we are on the same page. I was always of the mind that the micro-controller drives the FET's gate to turn on/off the load; the controller is responsible for & determines the flash rate. The FET is just the 'relay'. These are nice robust components these days - in the early period I toasted more than a few due to transients, lol.

Sorry I wasn't clearer - my bad

10-4 on the headlight circuit - I did notice that - it seems counter-intuitive at first glance. I'll think on it some more offline ...

Cheers bud.

 

a new relay is safer than resistors

 

Umm.. in this particular instance - there ARE no relays.

Generically speaking, if a relay was apporpriate/available it would be more efficient than load resistors. Safer? Not if sized/rated & installed correctly. (But yeah if someone were to strap a 1/4 watt unit to the fuel line ...lol) ...

There is already a big honkin' resistor in use for the DRL's from the factory.

OP - how is this going for ya?

 

Sorry I'm late to the party, but I just put in some LED towers in the turn signals and of course have the fast blinking. I have a few questions:

1.) Can you do anything else besides use a drop resistor in parallel? I'm just looking for some other way of doing this. Can the SJB be altered/programmed in anyway to change the wattage level at which the fault occurs? If not, what's the best way of doing a clean install of the resistors?

2.) If I leave it as-is, is there a risk of any damage or part failure? So far, I notice no other effects from doing this. i.e. All other lights work normally, including using the hazards.

Thanks!

 

And if your turn signals flash FAST with LEDS, why does the hazards flash the normal rate with LEDS?

 

The load of all 4 LEDs must have enough load on them, like 2 regular turn signals ?

If you have 1 burnt out bulb and use the 4 ways, I don't think they will flash fast with normal bulbs.

 

i know this thread has been dead forever but im ressurecting it. im trying to read all this and its confusing me more than anything. i installed LED plug in lights in my tails last week. Blinked fast until tonight. I bought 2 LED 3" lights to put under my tailgate net. Installed drivers side everything was fine. my blinkers worked and hazards worked. Installed pass side and that when my blinker, hazards, stop lights stopped working. Heres the wierd part...hazards work when headlight switch is off. Turn my running lights on and everything just stays constant like running light. but when hazards are on and switch is off my instrument panel flashs with them. What do i need to do to fix? Have one more fuse to check in morning and have to find relay but im super confused and been reading LED posts on forums for the last 4 hours.

 

i know this thread has been dead forever but im ressurecting it. im trying to read all this and its confusing me more than anything. i installed LED plug in lights in my tails last week. Blinked fast until tonight. I bought 2 LED 3" lights to put under my tailgate net. Installed drivers side everything was fine. my blinkers worked and hazards worked. Installed pass side and that when my blinker, hazards, stop lights stopped working. Heres the wierd part...hazards work when headlight switch is off. Turn my running lights on and everything just stays constant like running light. but when hazards are on and switch is off my instrument panel flashs with them. What do i need to do to fix? Have one more fuse to check in morning and have to find relay but im super confused and been reading LED posts on forums for the last 4 hours.

 

If I had to take a SWAG, I would say one of the new lamps is deriving ground from the parking lamp circuit.

This is just a SWAG based upon your post, if you can remove the passenger side lamp.
Confirm that with the driver's side lamp installed, that it operated correctly with and without the parking lamps and with and without the headlamps on, this would be a good 1st step.

I have very little to support this SWAG, but I am thinking very dirty brown wire ( parking lamp circuit ) being hooked to the ground on the LED lamp, and the black wire hooked to the tail part of the lamp..

 

The LED has one black wire coming out to splice in. It has an internal ground with mounting bracket. So I ran wire to blinker/stop/hazard wire. Drivers is lt grn with orange stripe. Passenger was light blue with orange I believe. Then I also spliced another wire into the LED wire and ran to Brown on each lamp which is running lights. I'm thinking maybe that I created a loop? Are the lights only running lights or blinker only?

 

If it is a single wire and the mounting bracket is ground, if I got that correct, you are right,you made a loop from parking lamp circuit to stop / turn circuit.

The brown wire is the parking lamp circuit, the other wires that you ID'd are stop / turn for each side.

If I got it correct, the LED lamp you have is a single circuit only.
Either to the Stop / Turn circuit on each side or to the parking lamp circuit on each side, but not both.