seventhgear

the logicon is not responding to me pressing the buttons on it... i recently put 134a in my a/c system to recharge the system.... well now the logicon is only sending the air through to the floor and its not even coming through the vents... its as if its coming from under the dash... (its hitting my legs on either side..... passenger and driver sides the air hits u at ur legs... only a little bit of air is flowing through the center vents... not much at all though.. and none through the door vents... what may be my problem??? it is fully recharged and the air hitting me at my legs is cold but i need it on my face...
thanks guys
jack

SureShot

The classic symptomes of "cold solder joints."
The solder joints where the connector pins meet the PCB tend to weaken. This can also happen to the light switch and the CPU.
There are many threads on this, along with some good web page write-ups.
I'm looking for the link I used to have on this.

seventhgear

i figured it was the solder joints.... damn....! how do i know which ones to solder? none of them have broken solders.... should i do them all ? but both of the logicons i have ... have that brown gooey **** on it... u know what im saying ? well thanks
jack

Turbonut

iTrader: (1)

If you don't want to do it yourself, PM Icemark. He does all the electronic repairs.

SureShot

That row where the connector pins meet the circuit board. You can see how the origonal solder didn't flow well when you pull the old solder off.

rotard

It's surprisingly easy. If you haven't ripped one out before (ya probably have, if ya got two of em) the trick is to just undo the one screw right under the windshield and pull out the big plastic/metal cover over the front vents to get to the infamous hidden plug. Then tie a string to the plug before you pull out the logicon.

I ended up soldering everything -- fun! Took hours, probably shouldn't have been drinkin'. Turned out it was the little motor for the hot-cold baffle, not the logicon. Had to get the car rollin' from the frozen north, so I just ripped off the lever and manually switched to "hot". Much nicer than freezin' my *** off for four hours!

Icemark

More than likely either the mode control mosfet, or the mode motor has failed, but check the plugs first if someone was doing air conditioning work. I almost always just pull the gauge cluster to get to the back plug (the one right above the air/mix motor), as it is much easier to feed the wires through, rather than trying to access it through the top of the dash. It is only about a 30 minute job to R&R the Logicon through the gauges.

The mode switches generally don't fail from cold solder joints (unlike the lights on thge mode switchs). You could try resoldering the back of the control panel, but remember you must remove all the old solder before you flow new solder in or you will have the same problem next year.

To test the mode motor (as posted dozens of times, in the large plug above the air mix motor, you'll have a car side and logicon side. You'll test the wires on the car side of the plug with the logicon unplugged. There will be a blue/yellow and a green. With 12V+ on the blue/yellow and ground on the green the mode motor should move all the way over to the vent position. with 12V+ on the Green, and ground on the Blue/Yellow the mode motor will move all the way over to the defrost position. With a meter on the two wires, you should see between 17 and 21 ohms of resistance. If this checks out okay, then it is the Logicon or connections to the logicon. If it doesn't check out as described above, the you have a bad mode motor and will need to replace it.

I have a couple of Logicons that are rebuilt right now as well, that I make available to RX-7club.com members at a discount. If you are intrested PM or email me.