BJ 70 rear defroster question

coldtaco · 01-06-05, 07:22 PM

Trying to trouble shoot my rear defroster. Replaced the fuse and the defroster on light stays on. Rear defroster does not work. Checked the continuity between the contacts on each door and found no continuity on the little door and have continuity on the big door. Got power to both doors. How many bad grids do you have to have to not get continuity? Do both doors have to work for them to work? If you can't fix the grids on the little door, can you run a jumper wire between the power leads to close the loop to make the big door one work? Any other ideas?

Stone · 01-06-05, 07:55 PM

The rear defroster indicator bulb stays on? Sounds like a switch problem to me. Have you taken your dash apart recently? What's the condition of your rear defrost switch?

coldtaco · 01-06-05, 07:59 PM

Well, the first time I tried using it, the light came on for maybe 30 seconds and then went out. Then it would not come back on even the next day if you turned it back on. So, yesterday I changed the fuse and now the light stays on when turned on. And the rest of the story is in the first post.

Stone · 01-06-05, 08:32 PM

Hhmm...if you blew a fuse then there was a short somewhere that blew that fuse. I would check the operation of your switch and make sure that's working. The way the FSM recommends that you check the grid is to use a voltmeter and some aluminum foil on the leads of your meter.

This is what it says:
INSPECT FOR WIRE BREAKAGE POINT:
(a) Place the voltmeter positive lead against the defogger positive terminal.
(b) Place the voltmeter negative lead with the foil strip against the heat wire at the positive terminal end and slide it toward the negative terminal end.
(c) The point where the voltmeter deflects from zero to several volts is the place where the heat wire is broken.

Another check in the FSM:

Inspect the voltage at the center of each heat wire as shown.

Voltage: Criteria:
Approx. 5V Okay (No break in wire)
Approx. 10V or 0V Broken wire

Note: If there are 10V, the wire is broken between the center of the wire and positive end. If there is no voltage, the wire is broken between the center of the wire and ground.

I don't know if you have the FSM or not, but I thought I'd post those up for you if they help. Good luck. FWIW, my defogger sucks too and I need to check it out sometime. Seems that the grid is okay, but it's SUUUUPER SLOOOOOOW...never really heats up enough to work, but I see faint indications that there is a tiny bit of current flowing through the wires.

roscoFJ73 · 01-06-05, 08:46 PM

Does anyone know how to fix/repace the demisiter grids.
Some of them were damaged after they made me take off the old window tint(lic inspector)
and now only half of them work.

Toyota said I have to replace the windows as they dont sell the demister grids and they want about $400 AUD to replace both windows

coldtaco · 01-06-05, 08:48 PM

I just finished doing that check. I got full voltage in the middle of each grid and even when sliding back and forth on the grid. I checked the electrical schematic and it does not show a timer. I don't know what the switch has to do with anything since I get full power at the terminal ends. Maybe these are just worthless?

coldtaco · 01-06-05, 08:52 PM

In the manual it lists a Dupont paste no4817. Don't know how easy to find. Find the break and mask off either side of grid line and then paste small amount over the break.

Stone · 01-06-05, 09:29 PM

Quote:

Originally Posted by coldtaco

I don't know what the switch has to do with anything since I get full power at the terminal ends. Maybe these are just worthless?

Well, didn't you say that you couldn't turn it off? Sounds like your grid is okay. If there's voltage then it must defrost the windows, right?...or not?

And you can get those repair kits for the grid from any auto repair shop. It comes in a tiny bottle and they are expensive. Kind of copper in colour. Good luck.

coldtaco · 01-06-05, 09:47 PM

I don't think I said that I can't turn it off? I think I said that I don't think the defroster works since I don't see any signs of it working, but doing all the checks, it should work. Kind of strange how I get voltage across the grid, but I can't get any continuity between the two terminal ends for the little window.

Stone · 01-06-05, 10:59 PM

Quote:

Originally Posted by coldtaco

Replaced the fuse and the defroster on light stays on.

Sorry Stephan...I guess i mesread your post. The wonders of internet.

Yeah, I don't know why you couldn't get a reading on the small window grid...dirty or corroded contacts maybe?

roscoFJ73 · 01-09-05, 06:08 AM

Quote:

Originally Posted by coldtaco

In the manual it lists a Dupont paste no4817. Don't know how easy to find. Find the break and mask off either side of grid line and then paste small amount over the break.

Thanks for that coldtaco.I found the directions in the FSM and will attempt a repair in the future

01-06-05, 07:22 PM	#1
coldtaco IH8MUD Regular Join Date: Jul 2004 Posts: 481	BJ 70 rear defroster question Trying to trouble shoot my rear defroster. Replaced the fuse and the defroster on light stays on. Rear defroster does not work. Checked the continuity between the contacts on each door and found no continuity on the little door and have continuity on the big door. Got power to both doors. How many bad grids do you have to have to not get continuity? Do both doors have to work for them to work? If you can't fix the grids on the little door, can you run a jumper wire between the power leads to close the loop to make the big door one work? Any other ideas?

01-06-05, 07:55 PM	#2
Stone IH8MUD Lifer Join Date: May 2004 Location: BC, Canada TLCA# 13772 Posts: 1,992	The rear defroster indicator bulb stays on? Sounds like a switch problem to me. Have you taken your dash apart recently? What's the condition of your rear defrost switch? __________________ Stone's Land Cruiser & Flyfishing Pics Flyfishing British Columbia: www.flyfishbc.com bcfishingreports.com

01-06-05, 08:32 PM	#4
Stone IH8MUD Lifer Join Date: May 2004 Location: BC, Canada TLCA# 13772 Posts: 1,992	Hhmm...if you blew a fuse then there was a short somewhere that blew that fuse. I would check the operation of your switch and make sure that's working. The way the FSM recommends that you check the grid is to use a voltmeter and some aluminum foil on the leads of your meter. This is what it says: INSPECT FOR WIRE BREAKAGE POINT: (a) Place the voltmeter positive lead against the defogger positive terminal. (b) Place the voltmeter negative lead with the foil strip against the heat wire at the positive terminal end and slide it toward the negative terminal end. (c) The point where the voltmeter deflects from zero to several volts is the place where the heat wire is broken. Another check in the FSM: Inspect the voltage at the center of each heat wire as shown. Voltage: Criteria: Approx. 5V Okay (No break in wire) Approx. 10V or 0V Broken wire Note: If there are 10V, the wire is broken between the center of the wire and positive end. If there is no voltage, the wire is broken between the center of the wire and ground. I don't know if you have the FSM or not, but I thought I'd post those up for you if they help. Good luck. FWIW, my defogger sucks too and I need to check it out sometime. Seems that the grid is okay, but it's SUUUUPER SLOOOOOOW...never really heats up enough to work, but I see faint indications that there is a tiny bit of current flowing through the wires. __________________ Stone's Land Cruiser & Flyfishing Pics Flyfishing British Columbia: www.flyfishbc.com bcfishingreports.com

01-06-05, 08:52 PM	#7
coldtaco IH8MUD Regular Join Date: Jul 2004 Posts: 481	roscoFJ73 In the manual it lists a Dupont paste no4817. Don't know how easy to find. Find the break and mask off either side of grid line and then paste small amount over the break.

01-06-05, 09:47 PM	#9
coldtaco IH8MUD Regular Join Date: Jul 2004 Posts: 481	Stone I don't think I said that I can't turn it off? I think I said that I don't think the defroster works since I don't see any signs of it working, but doing all the checks, it should work. Kind of strange how I get voltage across the grid, but I can't get any continuity between the two terminal ends for the little window.

01-06-05, 07:59 PM	#3
coldtaco IH8MUD Regular Join Date: Jul 2004 Posts: 481	Well, the first time I tried using it, the light came on for maybe 30 seconds and then went out. Then it would not come back on even the next day if you turned it back on. So, yesterday I changed the fuse and now the light stays on when turned on. And the rest of the story is in the first post.

01-06-05, 08:46 PM	#5
roscoFJ73 Diesel for blood Join Date: Jul 2003 Location: west australia Posts: 6,308	Does anyone know how to fix/repace the demisiter grids. Some of them were damaged after they made me take off the old window tint(lic inspector) and now only half of them work. Toyota said I have to replace the windows as they dont sell the demister grids and they want about $400 AUD to replace both windows

01-06-05, 08:48 PM	#6
coldtaco IH8MUD Regular Join Date: Jul 2004 Posts: 481	I just finished doing that check. I got full voltage in the middle of each grid and even when sliding back and forth on the grid. I checked the electrical schematic and it does not show a timer. I don't know what the switch has to do with anything since I get full power at the terminal ends. Maybe these are just worthless?

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