What voltage on heated seats?

[RTinGB]

Can anybody put a meter on their heated seats and tell me the voltage for low and high settings?

 

Thanks.

[dirtrider]

1 hour ago, RTinGB said:

Can anybody put a meter on their heated seats and tell me the voltage for low and high settings?

 

Thanks.

Evening RTinGB

 

I haven't ever measured the seat voltages on a hexhead but  they very well might be pulse-width modulated (pulsed power)  as that is a more efficient use of the power needed to run them rather than dumping the excess current into a resistor then having to somehow handle that resistor heat.  Probably 100% pulsed (on) for high & a percentage of that pulse-width for low. 

 

There is no external resistor for the front seat heating & the seat is powered & controlled by the ZFE (chassis computer) so resisting seat-low inside the ZFE would be asking a LOT for an electronic chassis computer.  

 

Due to the type of connectors on the hexhead heated seat it won't be easy to get a voltmeter on the terminals with the connectors connected without damaging the seals. (probably need the seat connected to the system to get a valid meaningful voltage measurement) 

[RTinGB]

Yup, kind of like trying to get a voltage from the rear running lights - I was afraid of that. Thanks for the post.

[beemer chuck]

I think dirtrider is correct on how the heat level is controlled.
There are four wires on the rear seat feed, so two must be seat power and ground, the the other 2 for signal to the ZFE. My guess wound be that the switch has an on, off and a resistor position for the low heat setting.  It appears that the zfe looks to see that the seat is attached but does not limit the seat wattage. A friend had a shorted element in a Sargent seat. Burned up the seat ground wire 24 inches back into the main harness. 

[dirtrider]

12 hours ago, beemer chuck said:

I think dirtrider is correct on how the heat level is controlled.
There are four wires on the rear seat feed, so two must be seat power and ground, the the other 2 for signal to the ZFE. My guess wound be that the switch has an on, off and a resistor position for the low heat setting.  It appears that the zfe looks to see that the seat is attached but does not limit the seat wattage. A friend had a shorted element in a Sargent seat. Burned up the seat ground wire 24 inches back into the main harness. 

Morning beemer chuck

 

The rear seat is different than the front as the rear seat has the on/off/hi/low controlled right at the seat rather than at the handlebar switch. 2 of the 4  wires are used for the actual seat heating (B+ & ground)  & the other 2 wires are used by the switch  to tell the ZFE if full heating power,  or partial seat heating power, or off  is requested. Both the high/low/off switch & the seat heating element use the "same" low (ground) return wire back to the ZFE. 

 

The rear seat switch simply uses those 2 control wires to tell the ZFE what to send power wise, therefore telling the ZFE to either send full power, or send pulsed partial power, or with both control wires open (not pulled low) to not send any power. (switch simply pulls the control wires low to tell the ZFE what is requested) 

 

Again I am not totally sure the rear seat heating is pulse-width-modulated for low but it has no external resistor & asking the ZFE to resist internally for low is asking a LOT of the ZFE's delicate circuit board so my educated guess (based on many years of working with similar module controlled circuits) is that the rear seat is also pulse-width-modulated for low, not resisted internally inside the ZFE.

 

 

[beemer chuck]

Yes, there are four wires to the rear seat. My guess is that there is a ground and power which is controlled somehow by the ZFE. This would allow for the start up check to see if the seats are electrically attached to the bike. I would think the other two wires are for controls signal to the ZFE probably pulling it to high, low, or open. I would think the handlebar switch for the front seat would be a similar set up where the switch sends a high signal to the ZFE Setting the heat level and the indicators on the dash. 

[dirtrider]

58 minutes ago, beemer chuck said:

Yes, there are four wires to the rear seat. My guess is that there is a ground and power which is controlled somehow by the ZFE. This would allow for the start up check to see if the seats are electrically attached to the bike. I would think the other two wires are for controls signal to the ZFE probably pulling it to high, low, or open. I would think the handlebar switch for the front seat would be a similar set up where the switch sends a high signal to the ZFE Setting the heat level and the indicators on the dash. 

Afternoon beemer chuck

 

My wire schematic shows the control 2 wires are pulled low to send requested heat command to ZFE. Pulled to the same low (ground) as the seat heater.

 

Looks like one is pulled low for high command & the other is pulled to low for low command as the switches show N/O at rest.  

[Joe Frickin' Friday]

On 1/1/2022 at 6:05 PM, dirtrider said:

Due to the type of connectors on the hexhead heated seat it won't be easy to get a voltmeter on the terminals with the connectors connected without damaging the seals. (probably need the seat connected to the system to get a valid meaningful voltage measurement) 

 

I have a Corbin saddle on my '09 RT.  I fitted it with a standard 2-pin connector like this one., which would make it easier to check the voltages/duty cycles while the seat is actually plugged in and working.  I'm currently shopping for a new DVM (my old one recently died); once I get one, I'll check this and  report back.

[Joe Frickin' Friday]

On 1/10/2022 at 10:24 AM, Joe Frickin' Friday said:

I have a Corbin saddle on my '09 RT.  I fitted it with a standard 2-pin connector like this one., which would make it easier to check the voltages/duty cycles while the seat is actually plugged in and working.  I'm currently shopping for a new DVM (my old one recently died); once I get one, I'll check this and  report back.

 

I got my new DVM and hooked it up to my saddle's wiring this weekend.  With the key turned to "run" (but the engine not running), I didn't measure anything in terms of voltage or duty cycle.  I'm guessing the seat heating circuit doesn't actually come alive unless the engine is running, and I don't plan to fire it up until ride time, which is probably a couple of months away around here.  Sorry.  If there's still interest at that point I can report back then.

[RTinGB]

My issue was figuring out what the switch on the side does, and I found that it simply grounds a wire in one direction (I), and the other in the other direction (II), and none in the middle. So it appears that it is just sending a signal back to the magic box as Chuck suggested.

 

Thank you for your input.