Temp Control Display

[DrewQ45]

90Q

I'm revisiting the well known Temp control display problem.

I had a unit in my car that refused to display for years except for the occasional or yearly visit where it would light up for a minute then fade into blackness again.

I recently changed my unit to another freebie unit (also has a bad display) because it was also not keeping the temp right. The new unit works great from an operational standpoint. From some posts on the yahoo site, I learned that flexing the IC board would sometimes cause the unit to light up again. It worked on mine so I took note of the direction of the flex then attempted to make it permanent inside the housing. I did this by cutting a piece of rubber hose (needed a non-conductor, least flammable material) and pushed it under the IC board causing it to flex upward. I reinstalled the unit and it stayed on solid for four days...that is...until yesterday. It went out and came back again.

Just wondering if any members have troubleshooted this thing down to component level and found the actual culprit. Resistor, capacitor, inductor maybe???

I know about the Jerry Tucker option but I'm saving that one for last since I'm in love the DIY approach. My next experiment will be to use a can of compressed air held upside down to cold blast the components. By rapidly changing the temp, I might be able to pinpoint the location of that sucker. Man I wish I hadn’t sold my O-Scope back in 89’

...Drew....

[maxnix]

Search lonallenq's posts and you will find it. Probably in the Infiniti Mechanics section.

[lonallenq45]

Hey Drew, long time no read...

That would be me. I never moved it to that forum (Infiniti Mechanics). So unless somebody else did, it should still be here in this forum.

If you are handy with a soldering iron you will most likely be able to fix the problem. Mine is still working since I fixed it. I keep thinking that one of these days it will go out again, but not yet.

My original post was on the Yahoo board, but Deesolballs was able to find it and posted it in the following thread:

http://nicoclub.com/zerothread?id=271

Good luck...

[DrewQ45]

Lon,

Thanks for replying.

I remember reading that post a while back. The first thing I ever tried was resoldering all possible joints when I tried to fix my old unit. It didn't work for me so I began to suspect a failed component as opposed to a weak solder joint. I may try to resolder all connections on the replacement unit just to see if there's a chance.

....Drew....

[AZQ45]

First...my display has been out for a number of months now. The unit, however, still works fine behind the scenes.

The Q was parked outside last night in the frigid AZ night (45 degrees, or so ). When I started it up this morning, the display was on for about a minute, then blinked off again.

Can someone explain what this so called 'thermal coupling' or 'amplifier' behing the glove box is? I suspect this is the problem.

[DrewQ45]

Your problem is the same as all the others that I've heard (mine included).

The failure lies within the IC Board which is inside the control unit. Somewhere on that board or in a component there is an open circuit. The open is very miniscule...small enough to be affected by changes in temperature. Solids expand and contract as temperatures rise and fall. When tempature goes down it causes the gap to lessen and close the circuit...enough to make contact for a minute. As soon as your car started to warm up.... it became an open circuit once again. Jerry Tucker in Calif has the fix for $100.

..Drew...

[lonallenq45]

First...my display has been out for a number of months now. The unit, however, still works fine behind the scenes.

The Q was parked outside last night in the frigid AZ night (45 degrees, or so ). When I started it up this morning, the display was on for about a minute, then blinked off again.

Can someone explain what this so called 'thermal coupling' or 'amplifier' behing the glove box is? I suspect this is the problem.

Mine did that too. Although the temperature swing is much less here on the west coast of Florida. The fact that it would work in the morning's cooler temps and then go out a few minutes later is what prompted me to try and fix it in the first place. Sometimes just heating up one of the surface mount components when you resolder them can either make them work like new or kill the component altogether. In my case, the flex test was confirmed to make the unit work (as long as it was flexed). I isolated the point that needed to be flexed down to an area the size of my finger tip. Then off to the solder station to resolder every component in that region. It has worked ever since. I guess the phrase "your experiences will vary" applies here. I would bet that Jerry Tucker just rebuilds the entire unit.