Test rear Window defogger with IR thermo?

[mike sampsel]

Wonder if I can test closed loop function of my rear window defogger with an IR thermometer? Has anyone done this?

[HarryD]

Not sure you can because the heated area is very small.

I have used a voltmeter to find breaks in a line.

[RDM]

I did- the heated area is the whole window, and if you have the IR thermometer close enough, the cone can be fairly small.

[mike sampsel]

Originally Posted by RDM

I did- the heated area is the whole window, and if you have the IR thermometer close enough, the cone can be fairly small.

Thank you Dru!

[RDM]

You can take a temp before you connect voltage. Then it's not hard to spot where the glass isn't warming, either with the IR thermometer or even through your fingertips.

I used the Permatex repair kit to rejoin broken heating wires. It's in this post:
SC Windshield / targa window seal replacement and trim refinishing

I also noticed that you posted a picture of your lovely car with the hopes you would do something big for her. Well, here you are!

[dannobee]

It's easier if you use a 12v test light. With the key and defroster on, ground your pigtail alligator clip to ground, then touch the grid with the tip of the test light. As you move across the grid, the test light will go from bright to dim. If there is a break in one of the wires, it'll be bright, then all of a sudden go off at the break. If it doesn't light anywhere on the grid, there's no voltage. If it's bright everywhere along the grid, the grid isn't grounded.

[GH85Carrera]

Th ultimate test is park it outside in below freezing weather!

We recently attended the Porsche Palooza in Eureka Springs, AR and one morning it was 24 degrees. My 911 had a solid coat of frost. I did not think to bring a ice scraper. I just fired up the engine and turned on the heat, and the rear defroster. It melted the frost in short order, starting at the pattern of the wires.

I will admit it is a not a real practical way to test the defroster, but it for sure is a way to know for sure. Oh, and my outside rear view mirror defrosters worked as well!

[mike sampsel]

Originally Posted by RDM

You can take a temp before you connect voltage. Then it's not hard to spot where the glass isn't warming, either with the IR thermometer or even through your fingertips.

I used the Permatex repair kit to rejoin broken heating wires. It's in this post:
SC Windshield / targa window seal replacement and trim refinishing

I also noticed that you posted a picture of your lovely car with the hopes you would do something big for her. Well, here you are!

Well I always wanted an IR termo anyway! And my mirror goes from 60 deg (F) to 110 deg pretty soon after the switch is on!

Sadly, there is no temperature change for the glass. Guessing a wire got disconnected during the install, doubt they were hooked up wrong, though wish I'd of take pictures of the connected wires. Too busy cutting pieces from the seal.

I'll be trying to unravel this puzzle, need for a defroster in AZ is rare though.
Will try the probe tests as suggested by dannobee above. Good luck to me Ha ha ha

[mike sampsel]

Originally Posted by GH85Carrera

Th ultimate test is park it outside in below freezing weather!

We recently attended the Porsche Palooza in Eureka Springs, AR and one morning it was 24 degrees. My 911 had a solid coat of frost. I did not think to bring a ice scraper. I just fired up the engine and turned on the heat, and the rear defroster. It melted the frost in short order, starting at the pattern of the wires.

I will admit it is a not a real practical way to test the defroster, but it for sure is a way to know for sure. Oh, and my outside rear view mirror defrosters worked as well!

Lol, it is the ultimate test to be sure, I think I'd fail it though

[mike sampsel]

Anyone know which side of the car the red/white wire connects to?

[HarryD]

Do this simple test.

Get a voltmeter or test light.

Turn on the defogger.

Ground the negative side of the tester and touch the positive lead to each of the terminals at each end of the glass. At one end, you should see 12 v or the light will come on. This will confirm power to the defogger grid.

If no power, you need to find out why. If power, you have broken wires in the glass. See my post above on how to test.

[mike sampsel]

So I found the red and white wire (stage 1) connects on the 1,2,3 cylinder side at line number 12 counting from rear of car up. I touched the connection and 12 volts!
Also little voltage drop across the same line over to 4,5,6 side.

I measure temp increase at the glass and see it go from 20 deg C to approximately 25 deg C in 10 min, so some heating occurs. The mirror goes from 65 deg F to 130 deg F in (not sure the time), almost fry eggs on the mirror.

So I guess stage one works. Tested my relay and stage 2 does not output 12 v, which is the cause of my r/bk wire having zero volts at the pig tail for the red/black line.

Conclusions and questions:

A.) Seems there must be connection to ground for heat to increase.
B.). Wonder if the temp of 25 deg C is as expected?
C.). Do I want to buy the relay to get stage 2 working in AZ?

What do my friends in Germany see for stage one temp increase?