How to Wire Current Latched output to control second Item.

[Car_modifier]

Hi all. I'm trying to figure somethign out. I have a Remote Starter that has the function of energizing the rear defroster (latched) for 10 minutes when activiated. I would like to know how to extend this to my heated seats (Mainly Driver side.) Would I just set up a relay to boost it (if so how) or just tap into the wire from the togle switch? (Hi, low, off) Should mention that the output wire from the starter supplies Negative 200mA Latched and pulsed (programmable.)

 

[BradtheRad]

You mention a toggle switch. Can you confirm the same switch provides power to the heated seat? Or does it go to a relay, and the relay provides power?

To heat the seat is likely to require an amp or two. If the toggle switch goes to a relay then you don't need to add your own relay.

The connection you add will need to cooperate with the existing system.

Can you get access to the switch terminals?
Can you get access to the fuse/breaker?
One might be more feasible than the other.

Can you measure current through the toggle switch? If it is less than 200 mA then it probably controls a relay, and you can hook your remote output to it.

However the negative 200mA figure is the wild card. This may or may not be compatible with what you have.

 

[Car_modifier]

Here is a diagram of the wiring

 

[BradtheRad]

We shall assume that C1 connects to the hot element (not shown).

The block that says 'Run-start A21' must mean you don't get power unless the engine is running. You will have to bypass this altogether. You'll need to find a live 12V wire to tap into.

I think you'll need to install a new relay. The power-carrying contacts will connect at (1) the 12V live supply, and (2) at the fuse clip.

The coil will connect at (1) your remote unit, and (2) at the return wire.

There are other components you might possibly use (scr, transistor, mosfet), but these are less convenient than a relay. Furthermore there is less risk of ruining your remote unit if you use a relay.

You will have to determine the best place to install the components.

I believe the easiest place to connect a new wire is at the fuseblock. This might be in the dashboard or the engine compartment. You'll either solder the new wire to the brass clip, or embed it in or beside the existing fuse/breaker.

On the other hand, can you get access to the Driver heated seat switch terminals? You could solder a new wire to that, and hook the other end to the new relay. It would depend on how you feel about bypassing the fuse.

- - - Updated - - -

 

[Car_modifier]

I think we're mixing things up... k I don't want the seat to have contant power (it only needs to be on when the car is running)
Currently when I remote start my car All the circuits are energized (Remote starter mimics Key in ignition and on the On/Run position) This allowes all my Accesoryies to function and the Remote starter sends out a latched signal to the Rear Defrost circuit (direct negative current) and runs it for 10 min (handy in canadian winters)

Specifiaclly what I want to do is take this wire and also link it to either Heat high or low to the driver seat to also engage the heat. It needs to mimic me pressing the button so that the BCM can monitor the temp so it doesn't over heat.

EDIT: The Switch MUX for the driver seat is located beside the left leg and is really easy to access. (Chrysler 300 seats)
Here is the diagram from the switch to the elements

 

[BradtheRad]

I think we're mixing things up... k I don't want the seat to have contant power (it only needs to be on when the car is running)
Currently when I remote start my car All the circuits are energized (Remote starter mimics Key in ignition and on the On/Run position) This allowes all my Accesoryies to function and the Remote starter sends out a latched signal to the Rear Defrost circuit (direct negative current) and runs it for 10 min (handy in canadian winters)

Specifiaclly what I want to do is take this wire and also link it to either Heat high or low to the driver seat to also engage the heat. It needs to mimic me pressing the button so that the BCM can monitor the temp so it doesn't over heat.

EDIT: The Switch MUX for the driver seat is located beside the left leg and is really easy to access. (Chrysler 300 seats)
Here is the diagram from the switch to the elementsView attachment 80680

Yes, I was unaware how your system works. I had the idea you would need to do all makeshift wiring. Some people are finicky to keep all safeguards in place. That is why my diagram speaks of tapping in before the fuseblock. (And that is what would cause you to have to leave the seat switch on the night before).

However now it sounds as though you will have power coming through the fuseblock as normal.

Since the switch is accessible, you can bridge across its contacts with the relay contacts. You won't need to leave the switch on the night before.

I get the idea your remote unit sends out a latched (continually 'On') signal for 10 minutes. Is that the case? If so then you can install an ordinary relay. It will be energized for 10 minutes and it will keep the hot elements on for that long.



Your new diagram shows modules. These are an unknown. They may or may not contain relays.

I'm not familiar with how your remote unit works. It produces a negative control signal and yet this would be compatible because it controls your rear defroster. I would not know how to give advice about applying the negative signal directly to the seat heater switch. It is simply easier for me to recommend using a relay.

 

[Car_modifier]

the Unit only has one wire (output signal) so I'm confused as to where to put the (return wire)

 

[BradtheRad]

the Unit only has one wire (output signal) so I'm confused as to where to put the (return wire)

The unit almost certainly is grounded to the chassis. Since I can't be sure, I wrote 'return wire'. I believe the return wire can go directly to chassis from the new relay.

Caveat, however...

Your guideline should be whatever is the arrangement for your defroster. Your remote unit puts out a negative polarity signal. I do not understand how this controls the defroster. Nevertheless since it works, it is likely to be able to operate the new relay too (as long as the negative polarity has its own path to ground). Does the defroster have a control unit? Then you should find out if that control unit is bolted to chassis, and if it has its return wire (ground) going to chassis.

By the way, all of this assumes there will be sufficient juice from the remote unit, so it will operate (or control) both the defroster and the new relay. You need to measure the signal from your remote unit. What volt level is it? Your relay coil has to be rated to activate at that volt level. Relays usually draw a few tens of mA. Will your remote unit supply that much current?

 

[Car_modifier]

alot of vehicles are negative switched... my rear defroster has a +12v signal until I press the button on my dash that supplys the ground.

Anyways No the remote starter doesn't have climate controls its a starter and just that.

Circut goes for rear defrost from BCM (Cars computer) to module that is at rear of car (This is the negative feed that my starter is tapped into)
Positive goes from Cars Fuse junction block directly to defroster module.

What I need to know is HOW to connect the negatve feed from the starter to my seat switch. Do I need diodes? relays... Polarity isn't an issue I already know how to switch that with relays.

I also need to know how to convert a Latched output to a single pulse using a relay or how to change single pulse to Latched

 

[BradtheRad]

my rear defroster has a +12v signal until I press the button on my dash that supplys the ground.

This clarifies things. Your remote unit apparently is bolted to chassis. It has a single free wire (per your post #7). When active, it grounds this wire... grounding the defroster, or grounding the module controlling the defroster.

In the same way you will ground the new relay coil. The other end of the relay coil receives +12V from anywhere at the seat heater control switch. You must locate a terminal carrying 12V (with the seat heater switch at Off).



When you combine the current through the relay coil, with all other current going into your module, the total must not exceed 200 mA. You can measure each individually with a meter, then total them.

By watching the current reading into your module, it will tell you whether its connection is for a second, or continual (for ten minutes).

I also need to know how to convert a Latched output to a single pulse using a relay or how to change single pulse to Latched

A clue would be whether your vehicle's defroster has an internal timer. Does it shut off automatically after ten minutes when driving? Some vehicles do this.

Similarly, does the seat heater shut itself off automatically? Or do you have to shut it off manually (flip the toggle switch)?