1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Replacing bulbs on HVAC (Logicon)

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Old 02-24-21, 10:28 PM
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Replacing bulbs on HVAC (Logicon)

I am going through my 85 gsl-se system by system and correcting issues that I discover as I do a restoration on the car. One issue is my heater control logicon works properly but when I press some of the buttons the light above the selected button does not light. I suspect a burnt out bulb. Much to my surprise I was able to order new bulbs and sockets through my local Mazda dealer as there where 9 still available in various depots across North America. My issue is I cannot seem to figure out how to remove the logicon from the dash. I have removed the center dash trim piece and the front screws holding the logicon in the dash but the unit will not budged. I assume there is stuff behind the panel holding it in place but cannot see a way to get at it. I don't want to break something by pulling really hard and make a small issue into a bigger issue. I tried searching for an answer but nothing specific to the fb comes up. Any help would be most welcome.
Old 02-25-21, 06:37 PM
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Remove the entire radio section with its associated additional 10mm bolts on each side. I think the Logicon is bolted to that sub-frame assembly with a strap across the back that will need to be removed, but it's been awhile since I was in there. Once you have the Logicon out, the screws holding it together are obvious, and the bulbs plug into the sockets by friction. Be careful pulling on the plastic plug connectors, as they're likely brittle and finding a replacement will be difficult. They all have snap latches that have to be released before they'll pull apart, so be cautious.
Old 02-27-21, 10:18 AM
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I thought I would follow up on what happened. I got the bulbs replaced and did not have to remove the logicon to do it. To replace the bulbs remove the two front screws holding the logicon in the dash. Then remove the two screws holding the clock in the dash and remove the clock. Then if you look under the front of the logicon you can see the bulbs and you can slightly move the logicon to get workable access to unscrew the bulbs.
Now with that said here is were you can run in to difficulty. I purchased brand new bulbs from Mazda. The new bulbs and base look identical to the old ones I removed but the new bulbs and base would not lock in place when installing in the logicon. After many attempts at installing the new bulbs and base failed along with many bad words I fixed it by carefully removing the burned out bulbs from the old bases and swapping over the new bulbs in to the old bases. Then the bulbs quickly locked in place with no issues. There must be a very slight difference between the old 36 year old bases and the newer bases.
Old 07-04-21, 01:22 AM
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Logicon look

Originally Posted by liondogs
I am going through my 85 gsl-se system by system and correcting issues that I discover as I do a restoration on the car. One issue is my heater control logicon works properly but when I press some of the buttons the light above the selected button does not light. I suspect a burnt out bulb. Much to my surprise I was able to order new bulbs and sockets through my local Mazda dealer as there where 9 still available in various depots across North America. My issue is I cannot seem to figure out how to remove the logicon from the dash. I have removed the center dash trim piece and the front screws holding the logicon in the dash but the unit will not budged. I assume there is stuff behind the panel holding it in place but cannot see a way to get at it. I don't want to break something by pulling really hard and make a small issue into a bigger issue. I tried searching for an answer but nothing specific to the fb comes up. Any help would be most welcome.
Look under each button. Bulb is cam screw in twist out twist new one end.
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