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Subject: how to repair rear defrost/defogger Author: shogun (moderator) : member since March, 2004 : 12995 posts Posted on: 2007-10-15 08:46:17

As winter is approaching soon, here my link from last year.

the evergreen for winter time.

Additonal info:
The control is made by the IHKA control module.
The white connector at the back of the IHKA control module is called X610.
Pin 7 goes to the relay for defogging
pin 24 goes to relay K8 for front window heater (wiper base).

The pins are from left to right
13 12 11 10 9 8 7 6 5 4 3 2 1

26 25 24 23 22 21 19 18 17 16 18 14


So, if nothing helps, also open the IHKA module and resolder it.

More info with regard to IHKA
To start with the repair, this explains you the whole system
IHKA Components

and more info
Driver side Passenger side tundra, why?

IHKA circuit board photos

German IHKA manual

and from alfaguy
IHKA tech info

Attached are two somewhat fuzzy photos of the main unit's circuit
board, they show the discoloration from heat, an you can make out the cracked solder joints on the reverse side that belong to the two large resistors.



When there is a problem with the IKHA, usually people suspect the control panel, the sword, water valves, and very often the flaps and stepper motors. Flaps and stepper motors are simple things and can be checked very easy.

The sword's only function for the IHKA is that it is controlled/gets signals from the IHKA module, which sits behind the sword and has 4 plugs (white, blue, yellow, green, 2 each side). The module is basically responsible for the whole IHKA functions AND (what many people do not know) also the rear window heater.

Inside the IHKA module there is the CPU for the temperature feelers, stepper motors, heater valves, which only carries out the orders (settings) thru the control panel in front of the driver and just acts according to the programs (which you select by pushing the buttons) selected by you. So the module is the heart of the whole system or better to say the brain.

There are about 30 different modules available, depending on the options in the car when it was once ordered. So, when you buy a spare module (which I recommend for testing and emergency (used one is much cheaper)), first check the part number on your installed module.

Resolder all points in the system, even if you do not see haircracks.

Also when you remove the module in case there might be a defect, usually they can be resoldered/repaired. Also have a look at the connections where the 4 arrows are, which sometimes get loose or have a short connection.



E32 750iL 11/88, E32 750iL Highline 03/90
7 series Tech tips
http://tinyurl.com/3486c

• how to repair rear defrost/defogger (pic) (url) - shogun 2007-10-15 08:46:17 (4521 views)