Retro fit heated window elements

Hi,

I am hoping someone can help I have two small windows in each side of an old 110 Land Rover Defender, which I would like to install heated window elements. I have the kits supplied by Holden Vintage and classic parts **LINK**

I am OK with the general procedure to install and all the required wiring but what is not sitting comfortable with me is the CUT TO LENGTH of the horizontal strips. Why I am not comfortable is the windows I intend fitting them to are half the size the kit is capable of covering.

My question is if I just cut them to my correct size (which is half the size they are capable of covering) will I be changing the resistance of each horizontal strip and altering the heat output at which the completed installation should work?

The instructions (they are in the link) give a size stipulation for the height I am OK with that it is just perfect for my application.

I could fit double the number of horizontal strips would that help or hinder?

CT

Hi CT,

If you only use half the strip length, you will only need half the voltage !

Using a closer spacing might overheat the glass locally.

You could use half on each window and put the elements in series and use 12 volts.

Have you asked the guys at Holden? They're pretty good chaps to talk to....

Cheers, Colin

You could use half on each window and put the elements in series and use 12 volts.

John likely has the best option to get around the problem.

Probably a strip of parallel resistors (heating elements). LED lamp strips use the same idea. They work at 12V however much is cut off, only the current drops,

Not like old-fashioned xmas tree lamps where each bulb failure puts more volts on the others until they all go pop.

Dave

How long are they and what is the wattage of the full length - does it say in the instructions? Just wondering what model engineering use they might have, like waming a tool drawer.

+1 on what John Baron says - this is what you'd do for Morris Traveller rear windows i.e. two panes half the car width (roughly).

Can't quite get my head around how SOD's Xmas lights are wired to give that effect though?

Rob

As said, wire the two panes in series and its the same as one big one anyway.

Hi CT,

Looking at the instructions with the kit contents in your LINK I think you will require two more of the vertical strips if you are going to fit out to two windows. My guess is they make contact with only two of the three strips at each end.
I note one spade connector is up and on the other side is pointing down so you end up with three lengths of triple wire tape forming the circuit.

I guess you should see if Holden will supply you with two extra vertical strips to let you use your spare element strip on a second window and then wire the two assemblies in series to avoid the chances of overheating.

HTH
Bob D

From what I can see, if it's half the length of recommended, you will end up with twice the current for obvious reasons, as mentioned above, one way would be to follow the instructions , but wire the two windows in series.

Assuming your concern relates to width rather than height, that is a shorter heating strip drawing too much current;
I think I'd approach it differently, at least investigating an alternative method; the kits seem to have 0v on one vertical rail and +12v on the other, so one connector each side of the window.
I'd look at running both wires to the same side and split one connector bar in half. Stick that to one side, and the full length one to the other.
Use half the heating elements at the top and the other half to the bottom of the split connector bar, and all commoned together at the other end on the full length bar.

That way, you effectively have two smaller windows wired in series on each side.

Bill

Edited By peak4 on 10/10/2020 21:56:56

Gentlemen,

Thank you for your replies, i have purchased two kits to do the job . Yes it would be nice to have done the job with one kit but I would be the two vertical pieces short.

Nevertheless having two kits I will use them. I believe my none electrical brain understands what you are telling me but please can someone confirm this way will be correct please.

I fit the window heaters as per the instructions using both kits one on each window. Now because I will have halved the length of each heater my connections will be as follows:-

Left hand window attach the positive cable to the left hand terminal, right hand window attach the negative cable to the right hand terminal.

Now the other two connections join them together to complete the circuit.

This installation will give the heat the kit intended.

Please accept the other part of the wiring like switch and fuse I am OK with.

Thank you in advance

CT

Yes, that's exactly right

Rob

This is what I was thinking of per side

|~~~~~~~~~~~~~~~~~~~~~~~| two half length strips on the right
|~~~~~~~~~~~~~~~~~~~~~~~| one full length on the left.
|~~~~~~~~~~~~~~~~~~~~~~~| Same plan for the opposite side
|~~~~~~~~~~~~~~~~~~~~~~~| which would save having the
|                                            +12v   two windows in series.
|
|                                              0v
|~~~~~~~~~~~~~~~~~~~~~~~|
|~~~~~~~~~~~~~~~~~~~~~~~| 
|~~~~~~~~~~~~~~~~~~~~~~~|
|~~~~~~~~~~~~~~~~~~~~~~~|

It would effectively double the heater length per window.
Bill

Edited By peak4 on 11/10/2020 20:23:44

I would follow bill's suggestion

Which would double the heat output on each window !

Bill,

It's not quite like the drawing nor modern heated windows, the power zig zags so one window is a single resistor not several in parallel. The ends must have breaks in them.

Bill, these windows are only half the size of the window that these heaters are intended for, so if you use all the elements in one kit for each window you will have all the applied heat in less than half the area.

Using your scheme you would need to apply half the rated voltage on each window which putting them in series will achieve.

Electrically one end of one window element would be connected to the frame/body/chasis and the other end linked to one end of the other window element, the other end of that element would be supplied with 12 volts via a fuse and a switch.