bloodvette

I looked over the schematics of our heated seats and it looks like it can't be done because the heated seat buttons are right in the electronic automatic temperature control module (EATC). So really there's nowhere to parallel a relay contact to simulate pushing the button. And you can't put direct power to the seat elements becuase they have a thermistor for temeprature control and direct power would just stay on full heat and burn out your seat elements in a few minutes. HOWEVER, I'm looking into disecting the module, soldering 2 small wires off the contacts of the push button for the driver's seat, to an auxillary contact from the remote starter OR a totally seperate relay's set of normally open relay contacts, then power this relay with a momentary pulse generated by a timer circuit that will trigger a few seconds after a command start has been initiated. (not during because all accessory power is disabled). To make the timer circuit would take some time (obvisouly you have to be quite knowledgeable in electronics) and I'm sure it would be very fine soldering on the interface board where the pushbuttons are, but I think it can be done. I've done some other interesting electronic projects I think this may be my next one!

has anyone ever attempted this? Everytime I think about doing this I say forget it, I can just press the button when I get in. Especially if the truck is already warm from the remote start then who really needs a heated seat. But I think it would be a fun project.

rrogers1221

very curious to see how this turns out

jayson_waltz

could do your idea, or ask an install shop how they do it. cause it is very possible with a relay or two, its done quite often and hooked up the the autostart aux button.

bloodvette

I'm sure it's a very common request, but I don't think it's ever done on our style of truck becuase, like I said, the buttons to turn on the heated seats is built right into the EATC module. and out of this module is a communication bus to the heated seat modules so really there's no where to tap in- other than the button itself.

I'm sure some other vehicles have it much less complicated and maybe the remote switch is directly wired to the heated seat modules so theres a pair of wires to tap into in that case.

The problem will be trying to do the fine soldering onto the board of the pushbuttons and try route the 2 small wires out of the casing. I'll have to take it apart and see how difficult it looks. Will report back.

j

D94R

I'm assuming this is just your opinion and not Ford fact.

I can not figure out why Ford put a 10 minute timer on our seats though. It seems like my butt just finally gets warm in the coldest months and it shuts off. If it's because the elements can't take prolonged heat then that's a fail on Fords part. My coworkers Jetta has heated seats that get just as hot as mine and his can stay on indefinitely, same with most (if not all?) of the aftermarket heated seat kits.

htrk1

white/red is drivers, white.yellow is passenger. neg. pulse, NOT latched.
@ the switch under the radio. I don't think you should need a relay as long as the system you purchased has this out put. Here is a thread that may be helpful.

http://www.the12volt.com/installbay/...0+heated+seats

bloodvette

I hate the 10 minute timer too! my Cadillac STS seats stay on. and they get hot so much faster and much warmer. The heated leather seats in the caddy is why I insisted on black leather heated when i was looking for the truck- hents Lariat. but the truck seats take so long to warm up and they don't get hot... I'm almost home from work when I can feel them. (7 min drive). not impressed. which is why I'm doing this project so the seats are warm when i get to my truck.

ANYWAYS, regarding your comment about the seat elements, Our heated seats are designed with a temperature controller under the seat. It determines the seat temperature with a thermister (resistance varies with temperature) and controls the output to the heating element accordingly. IF you look at the schematic for your seat you will see what I mean (if you're versed with electronic schematics.) The reason for this, is just like turning on a hot water tank with no water in it, it will burn the element out if the temperature goes high enough- which, rest assure, it will. This is why the thermister and controller is there to back off the power to the "Final control element". so that heated seat power is turning on and off every 30 seconds I would estimate to satisfy the thermister feedback and ultimately your seats temperature. It is possible but less likely that the output signal is designed to be modulating where it may find a happy medium of 8V to keep the seat at the proper temperature. but on/off control is the likely method chosen becuase of the inherent slow response time of heating a seat.

So that being said, if you forced 12V to your heated seat element, I would estimate about 10 minutes, your butt will get very hot, but then it will go back to normal becuase your heated seat element burnt out.

See some cheap aftermarket ones are just on or off from a switch, but that requires constant attention. OR maybe its a low wattage that can run 100% duty cycle without burning out. regardless the system we have in our seats is the best. I'm sure a fellow could tie in a properly sized resistor in series with your thermistor to alter the feedback signal and therefore alter the output signal- and ultimately raise or lower the seat temeprature. Of course you would be sacrificing longevity as the elements would be stressed if you run them hotter than they're meant to be. something to think about.

j

D94R

Yup, I'm versed in electronic schematics, being an Electronic Engineer Do you have the schematics handy?

You say the heated seat power is getting switched every 30 seconds. Is this during warm up, or after max temp is reached? You weren't real clear there.

Anyhow, this still sounds like a "what were they thinking" moment coming from the Ford engineers. You said your STS seats stay on. My buddies Jetta's seats stay on. I've known people with aftermarket kits that can stay on. And no one I've known has had issues with the elements dieing. That reasons to state that there should be no reason my seats can't stay ON after 10 minutes, if even at a reduced temperature (which would be preferable). They don't though. After 10 mins they are OFF completely. No continuous on off switching or low temp maintenance. Though to be honest, by that point with the heat running there really is no need to keep them on, but sometimes a few extra minutes sure would be nice.

bloodvette

yea sorry i wasn't clear. yea that was confusing. ok, when i turn on the heated seat in my cadillac they will not time-out. It will stay on for the duration of my drive. if I drive for 4 hours straight, that heated seat button is illuminated and my butt is toasty.

In the ford truck if I put the heated seat on, after ten minutes, the light on the button goes out, and the seat goes cold. If you press the button for the heated seat, you have ten more minutes of heat and again it times out.

none of the above is in regards to the dutycycle of the heat command to the seats. Being an electronic engineer, I'm sure you understand the controls aspect: When the heated seat button is illuminated, the controls are activated. The heated seat controller controls the output to maintain the temperature setpoint (measured by the thermister). So essentially power to the heated seat is turned on and off and on and off. I used 30 seconds as an example of the duty cycle- however not to be confused with the ten minute time-out I mentioned earlier in this post. Now, the duty cycle of the heat command, I don't know, 30 seconds was a guess. The way to find out is to put on a DC clamp on Ammeter on the heated seat wires which are accessible from the rear if you reach under your seat.

D94R if you would like to see the schematic I can email it to you. At this point I have confirmed that the WH-RD wire (for the driver's side) will infact turn on the heated seat when given a gnd pulse.

D94R

Ok, got what you meant with the 30 second cycle now. I wasn't sure if were just giving an example, or if that was the real sequence for the heat control.


Anyhow, with all this talk, this still doesn't explain why Ford has the 10 minute timer and your STS and others that I know have no timed limit for the seats to be ON (which was my main point with my original post). You say to keep the elements from dieing, but if that's the case then I reiterate that it's a fail on Fords part, either by choice of element, or heat control.

If you had the wiring diagram as a photobucket image or something I'd take a look, but I'm not really interested enough to worry about swapping emails. I just wanted to know if anyone had a solid answer why there was a time limit on our seats and not with other vehicle manufactures. Burning up the elements surely is a good point to consider, but I don't think that really is an issue if millions of other cars can have continuous heat on the seats and not "burn out in a few minutes". I'm not saying you are wrong, however; I don't think that is really a viable concern.




On a note about our trucks though. I can not immediately press the button for the heated seats after it goes out and have the seats turn back on. I usually have to give it 5 minutes or so before the circuit will allow active control of the heat again. I don't know if there is an internal cool down timer for the seats or not, but I can't immediately turn the heat back on. Yes I can press the button, and it illuminates the switch, but no heat until I give it a short cool down period first.