New power seats. How do I wire them?

aldolente · 02-22-2006, 11:54 AM

I purchased used power seats for my 1980 Targa. I am doing a complete restoration and wanted to move to a power seat off a newer carrera.
The seats are sport seats and have three wires. Oner is brown so I know this is ground. None of the wiring diagrams show how these seats should be wired. Anyone know what fuse block and amp fuse to use? Anyone with a wiring diagram?
Also, I am very tall and need to lower my seats. My body shop said they can do that. How much can I drop the brackets and still have operating seats?
Al

Kroggers · Kroggers's Garage

OK - been there and done it. what is the colour on the other two wires (black and red??), and do you have heated seats? If you say yes to all above then here is what you need. The red wire is for the seat adjustment, and the black wire is the hot wire for the heating element. As for the correct fuse to run them from, I had the same problem as you - no manual gives the info, until you look at the fuse diagrams for the later cars. I am travelling at the moment, so can not give you the correct fuse location for the seat adjustment and heater wires. If there is anyone on the board with the later style sticker on the fuse box cover, then they can have a quick look for you as it is listed there...

Just to be safe, I also included some additional in-line fuses on the wires that are by the connectors under the seats

aldolente · 02-22-2006, 01:01 PM

Thanks! Yes, the wires are Black and Red. I can't believe I bought heated seats! I live in Florida!
Guess I am just wiring up the red.
Let me know the location of the termination when you have a chance. I appreciate your help.

Kroggers · Kroggers's Garage

Hmmm heated seats in Florida

I will be back home at the end of next week, and will find the correct terminal on the fuse box for you. What you could do until I can get you the terminal (and to test it all), you could use the switched live going to your stereo

beamonk · 02-23-2006, 04:00 AM

I am curious as to the heated seats also. Isn't some relay needed for the heat element?

aldolente · 02-23-2006, 04:14 AM

Good question, John. I assumed that all the controls, switches and relays were built into the seat.
You know what happens when you assume!
Wish Pelican posted a latter electrical diagram that will help me.
Al

Kroggers · Kroggers's Garage

Where would you put the relay?? As both the switch and circuit is built in to the seat, all you have is the wires to the seat - putting a relay in the wire between the battery and the heated seat has no value. you would have to put the relay between the switch and heater element, and to do that you have to take the seat apart?!?

It is possible that the black wire is the signal wire for the heater, and most of the power is taken from the red wire. This is possible, as the red wire is substantially larger than the black one.

I will be installing a relay in the heated seat circuit (black wire), but only to operate an LED to indicate that the heated seat is on!

RoninLB · 02-23-2006, 04:47 AM

I ran a 10ga AWG wire from each seat to 2 15amp marine vapor-less circuit breaker next to the battery. It's powered with the key removed.

javadog · 02-23-2006, 06:21 AM

Al,

At the risk of leading you astray, I'll try to answer some of your questions. The brown wire is a ground that attached to the ground point on the left inner fender in the trunk, just in front of the driver's side hood strut attachment point. Look for all the brown wires disapearing to a common point under the wire harnesses on that side of the trunk. You might have to dig a little to find it. There's another ground point up by the fuse box and a dozen more scattered throughout the car. It probably doesn't matter much which one you use.

I have no idea which model year of car your seats came from, and Porsche's wire colors in their diagrams can't always be trusted anyway, so I won't quote wire colors for the power wires. The larger of the other two wires should be for the power seat motors. It will attach, eventually, to fuse 2 of fuse box 3. More on that, in a moment. The smaller of the two power wires is for the seat heating and it attaches, eventually, to fuse 1 in fuse box 3.

There are three fuse "boxes" in a Carrera. Right to left, you should have #2, with 8 fuses, then #1 with 10 fuses, the #3 with 3 fuses. The fuses for these two wires are 25A.

Having said all of that, the wires don't go directly from the seat to the fusebox. They are integrated with other wire harnesses. Also, other wires attach to these same fuses, so ou have to consider that, as well. I haven't compared a wiring diagram from a 1980 SC with a later Carerra or Turbo, to see what the differences are. Sometimes, when Porsche added a feature, they relocated some wires to other fuses to make room (load-wise) for the new ones. I'd suggest you get a copy of the two diagrams and compare them, before hooking anything up.

There is a relay associated with the seat heating. It is probably rectangular, with part number 928.618.521.00. I seem to recall they are located under the seats but I can't remember with 100% accuracy and none of my cars are at home at the moment for me to go inspect.

JR

Kroggers · Kroggers's Garage

JR, do you know what the reason is for the relay and how it interacts with the heated seat circuit? With the entire circuit located within the seat I am confused as to what the reason would be for the relay. Normally a relay would be used to remove load from ie. a switch, but as the switch is integral to the seat, I fail to see how the relay is used. As I did not wire in a relay, I would like to know if I need it or not.

javadog · 02-23-2006, 07:05 AM

Pal,

It's not a standard relay. Porsche calls it a delaying relay. It's been years since I used my heated seats in that car but, if I recall correctly, the switch has two positions in addition to rest (off) and they activate two different temperatures, low and high. It seems that if you select high, after 10 or 15 minutes it switches to low automatically. I don't have the car at home, so I can't go look, or read the manual. Perhaps someone else with a better memory, can chime in.

JR

Kroggers · Kroggers's Garage

Thank you for the information JR, but I am still confused about how Porsche manages this via just one wire? The "delaying relay" must have some way to know what selection you have made on the seat, and then at some point be able to change it for you? How does it do this? The only way I can see is to monitor the current used by the circuit (assume a higher current when on high heat), but I can not see how it can change the selection unless it is based on a pulse (like sending an on/off signal to the circuit). I would have assumed an additional wire to be there if a relay was involved to either act in line with the circuit between the heater element and switch or as a signal generator to the switch - but there is only one wire to the heating circuit?? It is possible that I am completely wrong here, as I just wired up my seats through trial and error and some experience with electronics

I am really interested to know how the circuit works when installed by the factory, so that I can change my DIY installation to be the same. At the moment it all is working (electric adjustment and heat), but I would still like to get it connected up correctly

javadog · 02-23-2006, 07:30 AM

Pal,

Don't confuse this relay with a standard load reduction type of relay. There are three wires from the seat heater switch to the relay. One is a power wire that is common with the power wire going to terminal 15 on the relay. In others words, it's the wire sending 12V power to both the relay and the switch. The other two wires output switched power from the seat heater switch to two different input terminals on the relay, A and E. Depending on which position you move the switch, you send an input to a different terminal on the relay. There is some sort of internal circuit or logic in the relay that takes this input and does something different to the power output to the heating elements.

Like I said before, I can't remember if there are two different output voltages to the heating elements, for different temperatures or if it is simply that the relay sends power to the elements for different lengths of time, thus affecting the temperature.

Have you looked under your seats to be sure you don't have this relay attached to the underside of the seat? Are you using the standard seat heater switch built into the side of the seat to activate heating? Are these seats from a later car (or a 928) that had a different seaat heating system?

JR

beamonk · 02-23-2006, 07:30 AM

One might try seat heaters.com for a harness to hook up the seat heater. I know that my heaters in my BMW are chock full of wires. I can't see that black wire as being just for heaters.

beamonk · 02-23-2006, 07:34 AM

My seats have the black wire, but no switch on the side for heat. I think they may have come from a 964.

Kroggers · Kroggers's Garage

Hmmm, this is getting interesting

I am not sure what age car my seats came from, only that they are for a car later than mine, and were in a really good condition. When I got them I removed the stock connector, as I could not obtain the factory wire harness to power up the seats - the original seats were manual... On the stock connector, there were three wires (should point out that the seats are 4-way electric and heated!!) - Brown, Red and Black. I connected up the Brown and Red first to activate the seat adjusters, but did not at this point have functioning heat. This I obtained by connecting the black wire to +12. Now I get heat if I press the heater button on the seat.

It is very possible that there is a relay already stuck to the bottom of my seat - in fact there probably is, as the heater does turn itself off after a given amount of time

) So, now that I think about it - you are probably correct, there is a relay thing on the heated seat system, but it is attached to the seat, and after the three wires coming from the seat...

Therefore, the way that i have wired up my seats would sound to be correct:
Brown = Ground
Red = +12
Black = +12

Thinking about it a bit more, I would probably assume that the black wire is there to provide the +12 for the heated seat relay and circuit, where as the Red wire supplies the power to the actual heater elements and adjuster motors. That would make sense as the Black wire is a lot thinner than the Red and Brown.

So JR, I think we are talking about the same thing but not the same point in the heated seat circuit

javadog · 02-23-2006, 08:39 AM

Pal,

The color of the two wires varies but one wire (the fatter one) is for the seat motors and the other wire is for the seat heating system. The heating elements are not fed with power from the wire that feeds the seat motors.

I'd say if you have 12V switched power (on when car is running, off when ignition isswitched off) to both your red and black wires, and you have them properly fused, you're probably good to go.

JR

Kroggers · Kroggers's Garage

Yup, I am good to go

aldolente · 02-23-2006, 08:58 AM

Look what I started!
It would be a lot easier if someone had a wiring diagram of both the seat and the wiring to the from the power source to the load. My seats are marked as recaro on the bottom but are OEM Porsche 4 way power seats. I believe they came off a 1987 Carerra.
The black wire may just power the coil of the heat relay. The switch may just break the or make the coil. Make sense?

Kroggers · Kroggers's Garage

Sorry aldolente. Let's start again - do you have a switch on the seat for heat? At least, you can connect the Brown to ground and the Red to switched +12 - and the 4 way adjustment will work.