Hello, I have an 85' Accord 1.8l 5 speed MT...

First, I could not determine when searching online if one horizontal defrost grid line, if scratched, would render the ENTIRE defrost grid unusable. I have only one grid line that I could find that is damaged and everything else on the grid looks good, even the tabs.

Rear defrost has maybe worked once in the 4 years I've had the car and I've decided it's time to get to the bottom of the issue with it.

The 20amp fuse in the engine compartment is solid. The button on the dash to activate the rear defrost lights up when pressed and a "relay click" is heard underneath the dash. I confirmed the correct relay by finding the relay that clicked by pressing the defrost button and then unplugging the relay and pressing the defrost button again.

Whilst the relay was plugged in, I hooked up my Ohm meter to the rear wire/clips detached from the grid and was reading 12.3v when both ohm meter prongs were touched against each alligator clip for the defrost grid. I also confirmed the volts turned to 0 when I pressed the defrost button on the dash to off.

Should a defroster still work if just one horizontal line is damaged and everything else is in good shape? I thought that it should work so that's why I am on here.


I'm willing to do whatever it takes to fix it at this point, Michigan winters are harsh!

 

Can you back-probe the power and ground connector at the grid and measure the voltage while the rear defrost is still connected? You may also want to measure the voltage from the relay power output to the positive side of the defroster while plugged in (voltage drop test).

Another quick test to rule out a weak relay is to swap the relay with an identical good working relay. Not sure what relays are identical on your 85 accord.

 

My 1999 LX's owner's manual says that the grids are very delicate and can be damaged easily, even when being cleaned (always wipe side to side, it says). Since it's a heating element and has a circuit going through it, I would imagine if one part of the grid is damaged that might cause the rest of it to malfunction, sort of like Christmas lights...but I'm not an expert.

 

Last night I probed both the prongs whilst the wires were connected. I was getting 12.3v. I then switched off the rear defrost button and it dropped to 0.0v - is that what you were asking that I do?

 

I know it's sensitive and I found a single break in only one horizontal grid line... I just am failing to see how one grid line can make the whole grid fail from heating.

See this link and the 2 pictures showing only one or two grid lines are cold but the rest are hot... that's what's confusing me. Is mine different that one break in one line on my 85 Accord will cause the whole system to fail - but won't on other vehicles?

Frost Fighter 2100 Defroster Grid Repair Kits

 

I'm not quite sure how to perform this voltage drop test as you described. If I have the relay in hand, what do I do?

Also, I have no idea where I can find another relay for the defroster. Isn't the defroster relay special in terms of having a timer or something? Or is my car too old that it doesn't have a timer and simply has the relay switch and that's it - as in the timer is whether or not the button is pressed on or off by the user? If that's the case then finding a relay will be simple I'm sure, I could try NAPA...

 

UPDATE: I went ahead and purchased a general, "all-purpose" relay you could say, from NAPA - part#: ECH AR355. This relay is listed under so many possible components using a relay. All the way from fuel pump, diesel fuel heater, A/C compressor, to automatic temp control relay and more.

I used my voltmeter and sure enough I discovered that I had been using it wrong previously. I apologize for that everyone.

So to correct my previous postings, before I bought the new relay I was using voltmeter and it did NOT show 12.3v like I thought, since I was using the wrong setting. What actually was shown was about 1.0 to 1.8v give or take to the back prongs. My old relay was very much faulty.

Now, the new relay does not "properly fit" as in it doesn't clip like it should, but it is really snug when plugged in so it won't fall out even if you let it dangle for the rest of its life.


The last test that remains is a cold morning...

 

WORKING!

Things that I've learned include not trusting a clicking relay, knowing my voltmeter better, and having a kick in the butt to get things done is the key success.

Here's a couple pictures (location of the part and more):