Wilks42

Yes, my HED looks like the 2017 picture. I just pulled the HED loose from bracket, slid up a little way on cables and used couple nylon ties around the tail and cables. The only reason the tail is on the HED is to secure cables to it but for some reason it was not done. HED's are used in aircraft. Not the most reliable sensor. It also depends on the body control module programming and how much tolerance is there for variations.

The Hall Effect Device HED that sense battery current in the 2016 is a donut looking part that both negative battery cables go through. The HED has a tail on it seemingly to bring the cables closer to the edge of it. I repositioned the HED closer to the battery terminal and used plastic ties on the HED tail to pull the battery cables against the inner HED ring. This would possibly provide a more accurate current reading. Did a test run on the seats. Initial reading of all four seats was around 59-61 degrees. Drove the vehicle around town noting seat temps. At the 10 min mark the pass seat ( unoccupied) was at 85-89 degrees. At the 15 min mark the pass seat was reading 91-94. Back was slightly warmer than cushion. Sitting in drivers seat, I first noticed warming at 7 min mark. By the 15 min mark I was ready to drop temp setting down. Both back seats came up to 90-92 degrees. My seats appear to be working like the other two vehicles I have tested. Took me about 15 minutes to fix after learning how the system works. I think the main issue was the battery cables not being snugged up to side of HED.

Maybe found the cause of this. I found the complete electrical drawings, theory of operation, etc for the 15/16/17 full size suv on gmupfitter. In my situation I have a new 2016 Yukon Denali which has front and 2nd row heated seats. Both the front and second row seat heaters operate but do it very marginal. My wife and daughter both feel the same way about all four seat heaters. Wife and myself went back to dealership and tested new 2017 Yukon denali to see if our vehicle is common operation with another. After 15 minutes on high in the 2017 we both felt toasty and wanted to turn the heaters down a level or two. Much different experience than our vehicle. The dealership talked to GM rep and the consensus was to replace all 6 seat heater elements in the four seats. This process took around a week to get done. During that time the dealership let us have a 2016 Yukon denali to use. The seat heaters in the 2016 worked much like the 2017 we sat in. We received our vehicle back and all four seat heaters are still marginal. Being frustrated with the situation I felt I have two options, live with it or figure it out myself. Spent 4 hours last night understanding the components and wiring for the seat heaters. The forward seats have separate upper and lower blowers which provide power to upper and lower heating elements. Separate power and grounds are provided to the blowers and heating elements. The 2nd row seats are similar in that one heater control module is in the left hand seat to control both seats. Separate power and ground are provided to the module and heating elements. The first thing in troubleshooting is to understand probability. What is the probability of all 6 heating elements being margin? low. What is the probability of the front and 2nd row heater control modules being failed in the same manner? low. What is the probability of separate ground wires being marginal in the same manner? low. What is the probability of four separate fuses and power wires being marginal? low. Nothing common to all four seats. Knowing that my vehicle is not common with two other identical vehicles, there must be a problem. Contrary to the dealership customer rep who said, That's just the way it is. After considerable reading this morning in the vehicle electrical manual a possible solution was found. The new body style SUV's have an electrical power management system. The purpose is to regulate alternator loads due to battery condition. This system measures battery voltage and battery current by use of a Hall Effect sensor. In the event of a sensed low battery requiring higher charging the power management system will go into a Load Shed. The first level of load shed reduces the heated mirrors, rear defrost and ALL Heated Seats by 20%. There is no indication to driver that load shed 1 is in effect. Thus a marginal battery and or marginal Hall Effect sensor could cause system to go into Load Shed and reduce the operation of all four seat heaters. What is the probability of a single part causing the marginal operation of all four seat heaters? High. If there is a GM Rep that can verify my findings, please do. Also, please NO "Very Sorry", "We Apologize", etc. This is the one thing GM customer support and dealership have provided me plenty of. The one thing I don't have is normal seat heater operation. My background, 27 year Aircraft Electronics Engineer / Integration Designer.

GM customer care routes you back to dealership. Dealership says nothing they can do that it's a GM issue. Never ending loop of BS

Have the exact same issue with heated seats barely getting warm on new 2016 Yukon Denali. After a 1 1/2 weeks at dealership getting all four seats heating elements replaced and instructed by GM rep, EXACT SAME PROBLEM. Loaner 2016 Yukon Denali seat heaters worked fine. Measures loaner seats with temp reader. 95 degrees after 15 min. Mine barely gets to 85 degrees. What a joke. Last GM vehicle we will purchase