Wiring question - bypassing ECU for rear defogger - Defender Source
Defender Source  

Go Back   Defender Source > Defender & Series Technical Discussions > Defender Technical Discussions


Reply
 
Thread Tools
  #1  
Old September 28th, 2004, 11:21 AM
dmarchand's Avatar
dmarchand
Status: Offline
David Marchand
'97 D90 SW Arles
Member
 
Join Date: Sep 2003
Location: New England
Posts: 2,862
Registry
Wiring question - bypassing ECU for rear defogger

I've got a small question I wanted to confirm with anyone else before I pulled the trigger. I'm wrapping up some of the wiring to-do's from my conversion, especially before winter. One of those is my rear window defogger. The '97's wiring runs through one of the ECU's in order to allow the ECU to time the defogger out after 15 minutes. Since my ECU is disconnected and removed. My poor defogger cannot be used. I have the wiring diagram (enclosed). I was looking to bypass the ECU (obviously), and wire from the relay, to the switch (no more 15 minute timeout). To allow the switch to kick the relay. The white/red from the switch, to the white/pink of the relay.

Should I be concerned about anything before I go and attempt this? Their are about 30 amps running through this relay, so I don't want to botch it and fry the relay, harnesses, etc. That would blow. Normally I have no problem with wiring, but with the increased voltage, I'm a bit timid.

Also, for those that own the '97. Is the relay for the defogger located within the center console, to the far left when sitting in the drivers seat? Just want to make sure as accesssing the back of those relays is a pain.

Thanks for answering. Hopefully the attachment isn't too small...
Attached Thumbnails
Click image for larger version

Name:	defogger (Small).JPG
Views:	233
Size:	35.0 KB
ID:	1507  
Reply With Quote
Sponsored Links
Advertisement
 
  #2  
Old September 28th, 2004, 12:06 PM
Mike Hippert's Avatar
Mike Hippert
Status: Offline
D-90Slut/Stalker,SNLPres
94 D-90 Grinding Rover
Member
 
Join Date: Sep 2003
Location: Manchester NH USA
Posts: 4,789
Dave the pic is hard to read, could you PDF it and repost it? It is a simple enough circuit to make, I think the hard part would be to find the correct wires to jump, if I understand it correct you only need the ECM to opperate the contactor on the relay, and if that is the case you only need a 12 volt timer and wire the timer off the ignition so it only comes on when the engine is running.
__________________
Don't forget to
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
first then ask questions later! The loose nut behind the wheel
Reply With Quote
  #3  
Old September 28th, 2004, 12:10 PM
dmarchand's Avatar
dmarchand
Status: Offline
David Marchand
'97 D90 SW Arles
Member
 
Join Date: Sep 2003
Location: New England
Posts: 2,862
Registry
Well to be honest. I don't really care for the timer. I know the implications of leaving it on. But the dash light is visible enough. I just want to bypass the ECU and switch the relay on/off when I please.

Try this PDF


Edit: I agree. I'm pretty sure it's simple 12 volt. I just want to get a second opinion of linking the white/red from the switch with the white/pink of the relay. As I said, I'm timid on this...
Attached Files
File Type: pdf DEFOGGER_REAR_WINDOW.PDF (36.2 KB, 215 views)
Reply With Quote
Sponsored Links
Advertisement
 
  #4  
Old September 28th, 2004, 12:29 PM
Mike Hippert's Avatar
Mike Hippert
Status: Offline
D-90Slut/Stalker,SNLPres
94 D-90 Grinding Rover
Member
 
Join Date: Sep 2003
Location: Manchester NH USA
Posts: 4,789
OK it's easy but there is a small problem. The trigger from the switch going to the ECU is negative or ground, and the on for the relay is 12 volts. So what you need to do is the WHT/RED wire from the heated rear window switch needs to be tied to WHT/PNK wire going to the relay. Both of these wires in the diagram go to the ECU and be connected at that point. The other thing you need to do is to connect the BLK wire on the heated rear window switch to the WHT/GRN wire at the ECU or the passenger compartment fuse box.

If you want to test it I suggest pulling the WHT/BLK wire off of the relay, this will disconnect the power going to the element and the defog warning lamp.

Sound good? Do I make sense?
__________________
Don't forget to
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
first then ask questions later! The loose nut behind the wheel
Reply With Quote
  #5  
Old September 28th, 2004, 02:33 PM
dmarchand's Avatar
dmarchand
Status: Offline
David Marchand
'97 D90 SW Arles
Member
 
Join Date: Sep 2003
Location: New England
Posts: 2,862
Registry
Aha, I see what your saying about negative switch Mike. Good one. Thus why I ask! And good point. I'll pull the brown grey and check with the test light that it has current.

Thank you chicken.
Reply With Quote
  #6  
Old September 28th, 2004, 04:00 PM
David T
Status: Offline
David T
04 Td5 Disco/98 Tdi Disco
Member
 
Join Date: Oct 2003
Location: Australia
Posts: 15
Try wiring thru' the ignition switch circuit and then the unit will work while ignition is on and can't be left on accidently and flatten battery Is done like this on my 110 SW
Reply With Quote
  #7  
Old September 28th, 2004, 04:45 PM
Mike Hippert's Avatar
Mike Hippert
Status: Offline
D-90Slut/Stalker,SNLPres
94 D-90 Grinding Rover
Member
 
Join Date: Sep 2003
Location: Manchester NH USA
Posts: 4,789
Quote:
Originally Posted by David T
Try wiring thru' the ignition switch circuit and then the unit will work while ignition is on and can't be left on accidently and flatten battery Is done like this on my 110 SW
If he wires it as I said it will only work when the ignition is on.
__________________
Don't forget to
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
first then ask questions later! The loose nut behind the wheel
Reply With Quote
  #8  
Old September 28th, 2004, 05:05 PM
dmarchand's Avatar
dmarchand
Status: Offline
David Marchand
'97 D90 SW Arles
Member
 
Join Date: Sep 2003
Location: New England
Posts: 2,862
Registry
Muddy Chicken is right on. On the wiring diagram. If I use the white/green to black, the switch is only being run from the passenger fuse box, which is only on in position II and III.
Reply With Quote
  #9  
Old September 30th, 2004, 11:21 AM
dmarchand's Avatar
dmarchand
Status: Offline
David Marchand
'97 D90 SW Arles
Member
 
Join Date: Sep 2003
Location: New England
Posts: 2,862
Registry
Mike and others. This all worked out. Only problem is I needed a latching switch to make it stay on. So for the meantime, I swapped the rear wiper switch (which latches) with the windscreen switch. You can pop off the front fascia and swap them. Always good when something like that comes together.

Now back to putting my dash and console back in place... What a pain in the butt.
Reply With Quote
Reply

Lower Navigation
Go Back   Defender Source > Defender & Series Technical Discussions > Defender Technical Discussions

Tags
ecu, wiring

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
NAS AC wiring question or call it a random wire question bjf Defender Technical Discussions 7 May 5th, 2009 09:58 AM
Bypassing Engine Imobilization ECU dmarchand Defender Technical Discussions 0 October 3rd, 2007 08:42 AM
ECU Question dbwitt Defender Technical Discussions 10 June 17th, 2005 11:44 PM
Custom wiring question Doug Defender Technical Discussions 7 December 15th, 2004 02:43 PM
Winch wiring question flippedrover Defender Technical Discussions 4 January 11th, 2004 09:20 PM


All times are GMT -5. The time now is 02:55 AM.


Copyright