2012 Mirror into 2009+ Truck, wiring in TEMP/Homelink

Tried both sides, gray wire and purple nothin

 

I think this just proves that the sensor is out of the range that the mirror is looking for. A resistor might work? I'd just need to know what range the mirror was looking for.

 

Might be a dumb question as I know next to nothing about electronics but are there a lot of resistor types and ranges out there? Are they expensive?

Would this theory be tough to test out?

 

Anybody try this? I would but I'm not even sure I would know what to ask.

 

The usually run between 50 cents to a few bucks at any electronic store. The big challenge is they come in a lot of resistance variance.

 

Definitely a range, but why this is not in the wiring diagram is beyond me. I think this also proves my point about the AC amp being the same part number. Somewhere else in the v6 trucks a resistor is modifying the output of this yellow wire? Gentex has to have this information otherwise they could not have created this mirror.

Edit: Maybe there is some resistor in the v6 models where the yellow wire is connected in overhead console or in the IN connectors down by the kick panel that everyone is missing. It could be shrink wrapped and no one is noticing it? This would seem like unnecessary wiring between platforms if this is the case.

 

http://www.gentex.com/product-support-request

You also need the serial number of the mirror which i don't have access to right now. I think the simple question is that you are trying to diagnose an issue and need to know what signal that model mirror is looking for on temp input pin. Type of signal and range or some kind of specification for diagnosis.

It should be a voltage = temperature thing where say 200mv = 50 degrees F or something to that effect. From the above it seems we need some really cold weather to even begin seeing the temp show up when connected ie: below 30 degrees.

 

BlackSeven: in trying to recall my limited electrical knowledge resistance is affected by wire size and length. You stated before that you ran your own wire from A14 up to the overhead console. This does not follow the OEM wiring which crosses the truck and passes through two connectors IN1 and IN2. Do you think this wiring and any varied gauges are creating the proper resistance required?

Resistance would be higher given the longer wires used in the OEM wiring setup. Correct?

 

So Jassco, does that mean your going to phone?

 

So can a mirror in a DC w/out home link be swapped for a mirror w/ home link? The only wire that would be different would be the wire needed for the home link. JAT

 

So I figured it out sort of....

You're right, sort of. It's not the wire gauging, but way the wires are connected. I've got some work to do with my voltage meter but there is too much resistance in the splices.

Got in my truck yesterday and the temp gauge was working!!!! It was at 118 degrees when it was about 27 degrees out.

There are two types of thermistors (The temp sensor). Positive temperature Coefficient and Negative Temperature coefficient.

The difference being that with increasing resistance a PTC Sensor will read hotter, and NTC will read colder.

It's my guess based on it being very cold when it read 118-120 degrees that the sensor is outside of the "Upper range" of resistance. Being that the incorrect wiring would only INCREASE resistance, I'm going to say that the Thermistor in our trucks is a Positive Temperature Coefficient Sensor.

That said, reducing resistance in the wiring from the A/C amplifier to the mirror should fix the problem.

I will do more testing with my Ohm Meter and report findings.

 

Thanks for your work on this Blackseven. Look forward to hearing what you find(wish I knew more about electrical and could help).

 

Awesome, but I have another observation. People in the V6 can just run a quick wire from their overhead console to the mirror and they get temp, so their wiring must have the proper resistance. Given I have an access cab with the yellow wire already in my headliner and connected I would assume this wiring is already of the proper resistance given it runs the same length/connectors as the v6. I wonder why myself and another here who tried don't get the proper temp if the wiring is stock.

 

If that's the case, stick a voltage meter (set to read ohm) In the end of the yellow wire coming from the amplifier, and take a reading of the current ambient temperature outside the truck.

Post your results, I'll post mine.

 

I just moved so finding that trusty meter will be fun, I may give up and just go to depot this weekend.

Edit: so you want the resistance of my wire from where the wire exits the A14 to where it connects at I8? Pull each end and test?

 

With the truck running check to see what the resistance is at the yellow wire pin in I8.

 

I tried this, sort of. I ran direct from the sensor, to the mirror, shortest wire possible, out the hood, thru the window, to the mirror, no luck.

 

This has nothing to do with the temp sensor. He means from the A14 AC amplifier connection behind the glove box and up to the overhead console. (The yellow wire in the 09+ trucks) We cannot do anything from the sensor to the AC amp because that has everything to do with the ECU and how it outputs the signal. Everything needs to be done after the AC amp because the mirrors are looking for whatever is output at A14....with the correct resistance of course.

 

So in all this research, did anyone end up getting all the various wiring diagrams? I am working on solving this in my 2010 but I can't find the wiring diagrams (without the subscription to TIS).

I am looking for specifically the pinouts for connector A28 for pre- and post- 2009 consoles as well as the truck wiring diagrams for pre- 2008 trucks.

My suspicion is that the mirror is indeed just measuring simple resistance accross the thermistor. The problem is finding what the temp- is going to. My assumption would be to ground, but I can't verify since I don't have a 2012. If that is the case then creating a ground-loop through the mirror might do the trick.

Alternatively I am thinking about modifying an existing accessory meter to work stand-alone without the overhead console.

 

I would figure someone would have the diagrams but a three day subscription is only $15. I would gladly pay that and get what you need if I knew what I was looking for.