Need some help with heated seat wiring.
09-23-2015, 05:53 PM
#1
Need some help with heated seat wiring.
I was having some rips on my wifes drivers seat repaired and got the idea to have them put some heated seat pads in while they had it apart. I went to the U-pull it and pulled the pads, wiring and switch from a late J30. The switch is the exact same switch that the Max would have and the only wires I cut are the power and ground.
I wired it up on the workbench and it only seems to be working on the low setting.
The pads are wired in series in series. The power goes in through the seat pad and out into the back pad. The back pad has a 3 prong plug so I'm thinking the high/low setting takes place there. I'm guessing the "high" portion of the back pad is faulty.
I can live with it only working in low if the pad is bad but is there something else I could be missing? Any other info would be helpful as well.
I wired it up on the workbench and it only seems to be working on the low setting.
The pads are wired in series in series. The power goes in through the seat pad and out into the back pad. The back pad has a 3 prong plug so I'm thinking the high/low setting takes place there. I'm guessing the "high" portion of the back pad is faulty.
I can live with it only working in low if the pad is bad but is there something else I could be missing? Any other info would be helpful as well.
09-23-2015, 10:27 PM
#2
The low and high heat of the seats are accomplished by controlling the amount of electrical current flowing through the heating elements. The seat cushion has 3 heating elements in it and the seat back has one heating element in it. The wiring together of these heating elements has a unique design that when combined with a dual pole, double throw switch, gives you 2 levels of heating.
On the low heat setting, the wiring has all 4 heating elements is series, so the electrical current has the most resistance, which means less current flow which means less than maximum heat from the heating element. The power enters the seat cushion, flows through all 3 heating elements and then into the seat back element and then to ground.
On the high heat setting, the 4 heating elements are now 2 sets of 2 elements wired in series. Two heating elements in the seat cushion in one pair and third seat cushion element and the seat back element is the other pair.
The electrical current comes out of the switch on a different pin from the low heat setting and enters the seat cushion through a different pin from the low heat setting. The power is applied between the 2nd and 3rd heating elements and then flows through the 2 sets of 2 elements. What had been the power input pin low the low heat setting is now connected to ground for this to work.
The seat back heating element has nothing to do with the high/low setting. And neither do the seat cushion heating element. It is how the heating elements are wired in conjunction with the switches.
Since you are getting heat on the low setting, that means that all 4 heating elements are good. There 3 things that could cause no heat on high.
1 - You didn't wire it correctly.
2 - You have a bad switch.
3 - This is something I didn't mention above. In the seat cushion pad, there are temperature sensors/current limiters. These are bypassed and not used for the low heat setting. But for high heat, the power coming from the switch now goes through these sensors/limiters in order to get to the heating elements.
I bet #3 is your problem. Based on the posts I have read here, this seems to be a weak point of the Nissan design. The heated seats in the 5th gen use this same 1990's design.
Here is a link to the wiring diagram for a 1996 J30. Look at page 141.
http://boredmder.com/FSMs/Infiniti/J30/1996/EL.pdf
On the low heat setting, the wiring has all 4 heating elements is series, so the electrical current has the most resistance, which means less current flow which means less than maximum heat from the heating element. The power enters the seat cushion, flows through all 3 heating elements and then into the seat back element and then to ground.
On the high heat setting, the 4 heating elements are now 2 sets of 2 elements wired in series. Two heating elements in the seat cushion in one pair and third seat cushion element and the seat back element is the other pair.
The electrical current comes out of the switch on a different pin from the low heat setting and enters the seat cushion through a different pin from the low heat setting. The power is applied between the 2nd and 3rd heating elements and then flows through the 2 sets of 2 elements. What had been the power input pin low the low heat setting is now connected to ground for this to work.
The seat back heating element has nothing to do with the high/low setting. And neither do the seat cushion heating element. It is how the heating elements are wired in conjunction with the switches.
Since you are getting heat on the low setting, that means that all 4 heating elements are good. There 3 things that could cause no heat on high.
1 - You didn't wire it correctly.
2 - You have a bad switch.
3 - This is something I didn't mention above. In the seat cushion pad, there are temperature sensors/current limiters. These are bypassed and not used for the low heat setting. But for high heat, the power coming from the switch now goes through these sensors/limiters in order to get to the heating elements.
I bet #3 is your problem. Based on the posts I have read here, this seems to be a weak point of the Nissan design. The heated seats in the 5th gen use this same 1990's design.
Here is a link to the wiring diagram for a 1996 J30. Look at page 141.
http://boredmder.com/FSMs/Infiniti/J30/1996/EL.pdf
09-24-2015, 07:50 AM
#3
Wow, thanks for the info. Trying to wrap my head around it.
The low and high heat of the seats are accomplished by controlling the amount of electrical current flowing through the heating elements. The seat cushion has 3 heating elements in it and the seat back has one heating element in it. The wiring together of these heating elements has a unique design that when combined with a dual pole, double throw switch, gives you 2 levels of heating.
On the low heat setting, the wiring has all 4 heating elements is series, so the electrical current has the most resistance, which means less current flow which means less than maximum heat from the heating element. The power enters the seat cushion, flows through all 3 heating elements and then into the seat back element and then to ground.
On the high heat setting, the 4 heating elements are now 2 sets of 2 elements wired in series. Two heating elements in the seat cushion in one pair and third seat cushion element and the seat back element is the other pair.
^ This part has me confused. The seat pad only has a two prong plug. How does it run different circuits through only two prongs? The back pad has three prongs. Did the installer swap the pads? The seat has a two prong plug and the back has three.
The electrical current comes out of the switch on a different pin from the low heat setting and enters the seat cushion through a different pin from the low heat setting. The power is applied between the 2nd and 3rd heating elements and then flows through the 2 sets of 2 elements. What had been the power input pin low the low heat setting is now connected to ground for this to work.
I noticed that the power and ground were jumping pins in the 3 prong plug as I switched from low to high.
The seat back heating element has nothing to do with the high/low setting. And neither do the seat cushion heating element. It is how the heating elements are wired in conjunction with the switches.
I hooked a test light to the two prong switch and it lights up brightly on low setting but not at all on high setting. It seems that I'm not getting any connection to the seat pad when it's on high.
Since you are getting heat on the low setting, that means that all 4 heating elements are good. There 3 things that could cause no heat on high.
1 - You didn't wire it correctly.
Doubtful only because the power and ground were the only wires I cut from the car.
2 - You have a bad switch.
I took the switch apart and cleaned it because it felt kind of funky. It does feel a bit loose but it does change the power and ground at the plug. Also, the light doesn't work. I was just going to solder in an LED. Would the bad bulb have an effect? I can go back to the junk yard and get the other switch.
3 - This is something I didn't mention above. In the seat cushion pad, there are temperature sensors/current limiters. These are bypassed and not used for the low heat setting. But for high heat, the power coming from the switch now goes through these sensors/limiters in order to get to the heating elements.
I bet #3 is your problem. Based on the posts I have read here, this seems to be a weak point of the Nissan design. The heated seats in the 5th gen use this same 1990's design.
You're probably right if it's not the switch. In the three prong plug I only get resistance through two of the prongs. 1 and 3. No other combo gives me anything.
Here is a link to the wiring diagram for a 1996 J30. Look at page 141.
http://boredmder.com/FSMs/Infiniti/J30/1996/EL.pdf
On the low heat setting, the wiring has all 4 heating elements is series, so the electrical current has the most resistance, which means less current flow which means less than maximum heat from the heating element. The power enters the seat cushion, flows through all 3 heating elements and then into the seat back element and then to ground.
On the high heat setting, the 4 heating elements are now 2 sets of 2 elements wired in series. Two heating elements in the seat cushion in one pair and third seat cushion element and the seat back element is the other pair.
^ This part has me confused. The seat pad only has a two prong plug. How does it run different circuits through only two prongs? The back pad has three prongs. Did the installer swap the pads? The seat has a two prong plug and the back has three.
The electrical current comes out of the switch on a different pin from the low heat setting and enters the seat cushion through a different pin from the low heat setting. The power is applied between the 2nd and 3rd heating elements and then flows through the 2 sets of 2 elements. What had been the power input pin low the low heat setting is now connected to ground for this to work.
I noticed that the power and ground were jumping pins in the 3 prong plug as I switched from low to high.
The seat back heating element has nothing to do with the high/low setting. And neither do the seat cushion heating element. It is how the heating elements are wired in conjunction with the switches.
I hooked a test light to the two prong switch and it lights up brightly on low setting but not at all on high setting. It seems that I'm not getting any connection to the seat pad when it's on high.
Since you are getting heat on the low setting, that means that all 4 heating elements are good. There 3 things that could cause no heat on high.
1 - You didn't wire it correctly.
Doubtful only because the power and ground were the only wires I cut from the car.
2 - You have a bad switch.
I took the switch apart and cleaned it because it felt kind of funky. It does feel a bit loose but it does change the power and ground at the plug. Also, the light doesn't work. I was just going to solder in an LED. Would the bad bulb have an effect? I can go back to the junk yard and get the other switch.
3 - This is something I didn't mention above. In the seat cushion pad, there are temperature sensors/current limiters. These are bypassed and not used for the low heat setting. But for high heat, the power coming from the switch now goes through these sensors/limiters in order to get to the heating elements.
I bet #3 is your problem. Based on the posts I have read here, this seems to be a weak point of the Nissan design. The heated seats in the 5th gen use this same 1990's design.
You're probably right if it's not the switch. In the three prong plug I only get resistance through two of the prongs. 1 and 3. No other combo gives me anything.
Here is a link to the wiring diagram for a 1996 J30. Look at page 141.
http://boredmder.com/FSMs/Infiniti/J30/1996/EL.pdf
09-24-2015, 11:15 PM
#4
The seat back heating pad has the 2 pin connector.
Based on what you said, it seems that the heating pads got reversed.
But you should get a lesser reading (like about 1/3) between pin 1 and 2 (35 & 34). This connection goes through the 2 temperature sensors/current limiters and one of the heating elements. Similarly, you should get a resistance reading of about 2/3 between pins 2 & 3. This would be going through the 2 temperature sensors/current limiters and two of the heating elements.
The fact that you only get a reading between pins 1 & 3 indicates that one (or both) of the temperature sensors/current limiters is burned out. This is your 'no heat on high setting" problem.
I'm going to try to explain the heated seat operation again in an attempt to to clear up confusion. This time I will use visual aids.
Drawing 1:
In the above drawing, I have colored the 3 parts of the heated seat.
The orange block on the top is the switch for turning on or off the heating pads in the seat.
The yellow block in the center is the heating pad in the seat cushion.
The small blue block near the bottom is the heating pad in the seat back.
Drawing 2:
In the above drawing, I have numbered the components in the heating pads.
1, 2 and 3 are the heating elements in the seat cushion heating pad.
4 is the heating element in the seat back heating pad.
5 and 6 are the temperature sensors/current limiters in the seat cushion heating pad.
Drawing 3:
In the above drawing, I have drawn a colored line indicating the electrical current flow through the heating pad elements for the LOW heat setting.
At the top of the drawing, the power comes from a fuse and into the switch. It goes through one of the switch contacts (called a "pole") and goes out of the switch on pin # 33. The power enters the seat cushion heating pad on pin # 33 (co-incidental numbering) and into heating element # 1, then into element # 2, into element # 3 and exits the seat cushion heating pad on pin # 35. From there the electrical current goes to the seat back heating pad, entering on pin # 35, goes through heating element # 4 and out of the heating pad on pin # 14 and then to chassis ground.
Drawing 4:
The above drawing shows the electrical current flow through the heating pad elements for the HIGH heat setting.
At the top of the drawing, the power comes from a fuse and into the switch. It goes through one of the switch contacts (called a "pole") and goes out of the switch on pin # 34. The power enters the seat cushion heating pad on pin # 34 and into temperature sensor/current limiter # 5, continues on through temperature sensor/current limiter # 6 and to the connection between heating elements 2 and 3.
At this point, the electrical current splits and takes 2 paths.
One path, indicated by the green line, the electrical current goes up and flows through heating element # 2 and then heating element # 1. The current leaves the heating pad via pin # 33 and goes back into the switch on its pin # 33. The current goes through a second set of contacts (pole) and back out the switch on pin # 14 and goes to chassis ground.
The 2nd path of the split electrical current, indicated by a blue line, goes down to heating element # 3 and exits the seat cushion heating pad via pin # 35. The current then goes to the seat back heating pad, entering on pin # 35 and into heating element # 4. After going through the element, the current exits the seat back heating pad on pin # 14 and goes to chassis ground.
This splitting (or not) of the electrical current is how the low and high heat settings are accomplished. On low heat, electrical current has to flow through 4 heating elements. This causes more resistance to the electrical flow and thereby reduces the electrical current. Less current means less heat from the heating elements.
By splitting the electrical current into 2 paths, The current only has to go through 2 heating elements. This is less resistance to the electrical flow so more current flows through the heating elements which causes more heat.
Last edited by DennisMik; 09-24-2015 at 11:21 PM. Reason: I wish I could type
09-26-2015, 10:17 PM
#5
Thanks for the info. That's way above and beyond.
I'm pretty sure the seat pad (now in the seatback) is partially bad.
If I hadn't done this on a whim I would have bought a generic set of pads that comes with a harness and switch. Now that this one is in the seat it's too late.
Do you know off hand what voltage the smaller pad (2 prong) can take? I was thinking of running power straight to it with a resistor to run it on "high". I'm assuming it can't take straight 12 volt without killing it.
I'm pretty sure the seat pad (now in the seatback) is partially bad.
If I hadn't done this on a whim I would have bought a generic set of pads that comes with a harness and switch. Now that this one is in the seat it's too late.
Do you know off hand what voltage the smaller pad (2 prong) can take? I was thinking of running power straight to it with a resistor to run it on "high". I'm assuming it can't take straight 12 volt without killing it.
09-27-2015, 02:12 PM
#6
I don't know the true answer to that, but based on basic electronics, it would be 3 volts for low heat and 6 volts for high heat.
As previously stated, there are 4 heating elements total. When the low heat is selected, the 4 elements are connected in series. This means that each element gets to use 1/4 of the power which is 12 volts. So on low heat setting, each element gets 3 volts.
For high heat, the wiring is re-arranged so that there are just 2 heating elements in series. So with 2 elements using the 12 volts, that means each one is working with 6 volts.
This is based on the assumption that all the heating elements have the same resistance. This is a detail I don't have any info on.
As previously stated, there are 4 heating elements total. When the low heat is selected, the 4 elements are connected in series. This means that each element gets to use 1/4 of the power which is 12 volts. So on low heat setting, each element gets 3 volts.
For high heat, the wiring is re-arranged so that there are just 2 heating elements in series. So with 2 elements using the 12 volts, that means each one is working with 6 volts.
This is based on the assumption that all the heating elements have the same resistance. This is a detail I don't have any info on.
11-18-2015, 07:30 PM
#7
Newbie - Just Registered
Join Date: Sep 2012
Posts: 3
Hi,
I'm trying to replace the blown seat cushion heating pad. Got aftermarket kit form Amazon.
I want to connect it to existing harness, but these new pads have 2 pins connector each (red and black), while original seat cushion pad has 3 of them ( red, white and yellow). Ok, red is going to red. And what should I do with other two?
I'm trying to replace the blown seat cushion heating pad. Got aftermarket kit form Amazon.
I want to connect it to existing harness, but these new pads have 2 pins connector each (red and black), while original seat cushion pad has 3 of them ( red, white and yellow). Ok, red is going to red. And what should I do with other two?
11-19-2015, 08:32 AM
#8
I don't know the colors of the wires going into the actual heating pad. Since the Nissan pad is a dual heat pad, 12 volts would be going into 2 different wires, depending on if the switch was in low heat or high heat. The third wire then goes to the heating pad in the seat back.
You want to have the black wire of the new pad go to the seat back. Follow the wire harness and see what color wire goes to the seat back or you could get your ohmmeter and trace it this way.
As for the red wire of the new pad, you cannot make the assumption that it connects to where the red wire of the Nissan pad connected. The Nissan red wire might go the the seat back, you have to figure out the seat back wire color first.
And because of the way the switch is wired internally, you want to make sure that you use the low heat connection. You might blow the fuse if you use the high heat side of the switch, not 100% sure of this, though.
You want to have the black wire of the new pad go to the seat back. Follow the wire harness and see what color wire goes to the seat back or you could get your ohmmeter and trace it this way.
As for the red wire of the new pad, you cannot make the assumption that it connects to where the red wire of the Nissan pad connected. The Nissan red wire might go the the seat back, you have to figure out the seat back wire color first.
And because of the way the switch is wired internally, you want to make sure that you use the low heat connection. You might blow the fuse if you use the high heat side of the switch, not 100% sure of this, though.
11-19-2015, 10:14 PM
#10
Newbie - Just Registered
Join Date: Sep 2012
Posts: 3
I don't know the colors of the wires going into the actual heating pad. Since the Nissan pad is a dual heat pad, 12 volts would be going into 2 different wires, depending on if the switch was in low heat or high heat. The third wire then goes to the heating pad in the seat back.
You want to have the black wire of the new pad go to the seat back. Follow the wire harness and see what color wire goes to the seat back or you could get your ohmmeter and trace it this way.
As for the red wire of the new pad, you cannot make the assumption that it connects to where the red wire of the Nissan pad connected. The Nissan red wire might go the the seat back, you have to figure out the seat back wire color first.
And because of the way the switch is wired internally, you want to make sure that you use the low heat connection. You might blow the fuse if you use the high heat side of the switch, not 100% sure of this, though.
You want to have the black wire of the new pad go to the seat back. Follow the wire harness and see what color wire goes to the seat back or you could get your ohmmeter and trace it this way.
As for the red wire of the new pad, you cannot make the assumption that it connects to where the red wire of the Nissan pad connected. The Nissan red wire might go the the seat back, you have to figure out the seat back wire color first.
And because of the way the switch is wired internally, you want to make sure that you use the low heat connection. You might blow the fuse if you use the high heat side of the switch, not 100% sure of this, though.
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