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| 5h4dy |
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 Hi everyone, I have an EB wagon, and the rear demister lamp on the dash stays on constantly. The rocker switch on the clock panel that turns it on and off doesn't light up, and pressing it has no effect. I changed the switch for another from an EA, and still the same issue... Any ideas? |
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| TedW |
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replace rear demister (can also be called backlight) relay - from memory located in interior fuse box
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| TimmyA |
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The rocker switch on the clock panel only lights up when you turn the parkers on... Not when the demister is on or off... It is so you can find it at night...
Can't help with the instrument cluster jewel being stuck on but... BEM turns it on and off and the rocker switch feed directly into the BEM... Cheers, Tim
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| 5h4dy |
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{USERNAME} wrote: replace rear demister (can also be called backlight) relay - from memory located in interior fuse box Tried that, took the one from my EA and still the same issue 
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| 5h4dy |
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{USERNAME} wrote: The rocker switch on the clock panel only lights up when you turn the parkers on... Not when the demister is on or off... It is so you can find it at night... Yes, sorry my post was a bit unclear - was meant to say that the rocker doesn't light up at all, with lights on or off and pressing demister switch doesn't appear to do anything |
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| Mad2 |
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check to see IF you have any power at switch & globe 'maybe' blown in switch
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| TimmyA |
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Hi,
Attachment: Relay should have power to one contact from the demister CB... Make sure the CB hasn't failed... If you have power there then make sure the BEM is earthing one side of the coil when you press the button... Try using a piece of wire to rule the button out... Isn't much to the system... Cheers, Tim
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| TedW |
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does demister warning jewel in dash light up if you leave relay out - if so does demister warning jewel in dash light up if you disconnect switch ?
switch turns bem on -bem turns relay on -relay feeds power to rear demist and warning jewel - can you hear relay switching - do you have power to rear demister ? Use TimmyA's wiring diagram may have lost earth to switch and warning jewel causing backfeed from bem to light up warning jewel check circuits to switch for illumination problem blu/red power when tail light switch on |
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| 5h4dy |
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{USERNAME} wrote: Hi, Attachment: EA EB ED Factory Manual Voumel 2.pdf Relay should have power to one contact from the demister CB... Make sure the CB hasn't failed... If you have power there then make sure the BEM is earthing one side of the coil when you press the button... Try using a piece of wire to rule the button out... Isn't much to the system... Cheers, Tim Thanks for that - relay appears to have power, but the demister button does nothing. I used a piece of wire to bridge the two pins on the plug for the switch, and still nothing. 
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| 5h4dy |
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{USERNAME} wrote: does demister warning jewel in dash light up if you leave relay out - if so does demister warning jewel in dash light up if you disconnect switch ? switch turns bem on -bem turns relay on -relay feeds power to rear demist and warning jewel - can you hear relay switching - do you have power to rear demister ? Use TimmyA's wiring diagram may have lost earth to switch and warning jewel causing backfeed from bem to light up warning jewel check circuits to switch for illumination problem blu/red power when tail light switch on If I remove the relay, then demister warning jewel turns off. Removing the switch has no effect. Attempted bridging the pins on the plug for the switch, and still nothing. If I leave the key on and remove / replace relay I can hear it clicking, so relay appears to be working. blue/red wire on switch has +5V when lights are on |
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| TedW |
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relay should only work when you remove /refit with accessory on,if you turn rear demist switch on
- put a "test light"across "power" and probe white wire at switch with switch disconnected and connected should only get earth when connected when you operate switch -if earth when disconnected possible body module fault keeping relay shunt circuit on -try disconnecting body module and reconnecting ................ put a led across blue/red and brown and turn taillight on |
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| 5h4dy |
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{USERNAME} wrote: relay should only work when you remove /refit with accessory on,if you turn rear demist switch on - put a "test light"across "power" and probe white wire at switch with switch disconnected and connected should only get earth when connected when you operate switch -if earth when disconnected possible body module fault keeping relay shunt circuit on -try disconnecting body module and reconnecting ................ put a led across blue/red and brown and turn taillight on Yes, you are correct, the relay should only work when it's on - I checked and the demister IS on, it's not just the instrument panel jewel, the demister is permanently on each time the key is on, which is odd since they usually reset to off each time the key is turned off. I probed the pins on back of the switch with a multimeter, and it appears that the white wire has +12V, and the black has earth... I will try the other tests you mentioned when I get a chance - trying to do it all in daylight hours when I'm not working. |
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| 5h4dy |
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Also, does anyone know if there are any differences between the BEM in the EB wagon and the one in an EA sedan? As I have an EA donor car sitting in the yard I can use to test parts...
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| TedW |
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susspect you have a BEM fault - can usually here BEM click when you operate demist switch-
check how many plugs between BEM's - different appointments determine suitability ie.electric windows etc. - plug it in anyway and see if demister works correctly -shouldn't need to wait for key to download to test demister - using a multimeter to test will show voltage backfeeding from bem as meter is more sensitive than a test light - using a test light connected to power will tell you if switch circuit is operating - if light stays on with switch connected but "off" recheck with bem disconnected - did you try unplugging and reconnecting bem - |
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| 5h4dy |
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{USERNAME} wrote: did you try unplugging and reconnecting bem - Yeah, tried that - instrument panel warning jewel stayed on the whole time, even while the BEM was unplugged.... |
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