Switch light lights up, but no defrost.
Checked the 40 Amp under the hood and is OK.
What else. Where are the contacts for the grid?

 

Does the car has climate control? If so, does the car have navigation? The circuits are slighty different for climate control (w/ navi) vs. climate control (w/o navi) vs. Manual A/C.

 

It's An EX-L 4 door, no nav

 

If the audio-HVAC Sub-display works or heated seats work, then it is not a problem with another fuse, Fuse 16 (7.5A) located in the under-dash fuse box.

The following is for information or educational purposes only. Due to the danger of the airbags inadvertently deploying, it should be performed by skilled technicians who have the proper tools, equipment, and training to correctly and safely maintain your vehicle.

With a voltmeter, with the defogger turned on; voltage can be tested at either or both of the following:

• At Connector C304, 8-P blue connector (located behind left kick panel), backprobe at the green wire to check for voltage with the defogger turned on. Backprobing is either using a backprobe set or using a thin needle or something and making contact with the metal terminal of the connector without piercing the wire in the back of the still connected connector. Care must be taken to ensure that the wiring does not get damaged. Voltage is checked by touching black lead to chassis ground, and red lead to backprobe at Grn wire.

• At Defogger connector A (at the left C pillar), disconnect the connector and with a voltmeter, voltage is checked with defogger turned on. Black lead to chassis ground and red lead to Grn wire connector A. Connector B is at the right C pillar is a ground connector. Both respective connectors are located behind the C pillar trim panels, where the airbags are. Since there are the air bags in that area, the negative battery cable must be removed from the battery for at least 3 minutes prior to any work. There are several different type of clips holding on the panel. One type is a non-reusable type, which must be replaced when the panel is removed (see attached pic.). A mallet is used to hit the area where the non-reusable clip is located to release that clip. The other clips pull out and are re-usable.

https://www.hondaaccordforum.com/for...-area-clip-jpg

Behind the right C pillar is also the ground G801 used by the defogger system, the ground wire from G801 leads up to connector B. This is checked to make sure it is connected and secure.

 

I don't think I'm going to like this

 

Well, the driver's multiplex integrated control unit (MICU) is in part of the circuit for the rear defogger. When the defogger switch, climate control unit is pressed, the defog signal is sent to the driver's MICU (integrated as part of the under-dash fuse/relay box). The driver's MICU provides the ground to the rear defogger relay, which energizes the relay. Battery voltage is then allowed through the relay to the rear window defogger.

You can always try a battery cable reset to see if it changes anything. Disconnect the negative cable (disconnect negative first) and then positive cable. Then connect them together with a jumper wire for 15 minutes. -- Do not touch the battery terminals.

You will need the radio security code afterward.

 

Here's something else to check. In the under-hood fuse/relay box, the number 8 relay is the rear defogger relay. Some of those relays in that row may be the same type of relay. If they are, try swapping the horn relay (#2) or radiator fan relay (#7), or any other that may be the same with the rear defogger relay to see if it is due to the relay.

 

Really appreciate your help with this. I'll try your suggestions today and get back.
Just wish I could get to the window terminals to see if they are getting voltage without so much trouble
Best way to test grid to see if it's getting current???
Mike

 

Never heard of this

 

See the attached pic., which is an excerpt from a January 2012 Honda Service News article. There have been other Honda articles which stated a different time to do the reset with the jumper wire and a slightly different procedure; such as 15 minutes without having to turn the ignition ON vs. 10 minutes and turning the ignition ON while doing the reset.