Solution To Flickering Fan Speed 2 Or 3 A/C PART 2

[pasadena_commut]

If the contacts have not overheated on your control unit (no plastic melting) before doing anything else it would be wise to put a voltmeter across the switch from the active wire to the ground (at the switch, not at some other point on the chassis). If there isn't a "big" voltage drop there (>0.1 volts) then look elsewhere for your problem.

Here is a slightly more in depth discussion (I have no connection to that company) of what you are looking for:

http://www.vestest.com/VDTestSwitch.pdf

Except on the P5 the test must also include the contacts on the wires at the back. That is, the voltage drop could be inside the switch or at those contacts. If there isn't a voltage drop anywhere it would be pointless and possibly counter productive to do anything to those contacts.

 

[jdwk]

You are right on referencing that article. Thanks for sharing that. It is a total resistance though and depending on age, environmental conditions, type of driving, etc we all have varying degrees of resistance. Some people can simply crimp the connectors on the wiring harness, some need to solder, some can clean the contacts on the switch, and possibly there is a board that is more tolerant of the IR drop. My supposedly updated board did not help, but MJO could have got some bad info as he and at least one other have claimed good results with swapping the whole unit.

Mine is working for now, but if it goes out again, I will come up with a more permanent solution. Something along the lines of a relay to bypass the current around the swtich, which another member suggested.

Oh and I read through this entire thread last night, and dielectric grease does not conduct electricity. If it did, your contacts would all be shorted inside the switch, as it is smeared everywhere.

 

[Zuntar]

My brain hurts now from reading years worth of posts and not really know whether to screw with it or not. Probably best to check it out and make sure nothing is melted. Serious kudos to all the hard work you guys have put into this issue.

 

[pasadena_commut]

My brain hurts now from reading years worth of posts and not really know whether to screw with it or not.

I just finished installing a circuit that fixes this problem - solid green compressor light on all fan settings now. Whether it will hold up over time, well, only time will tell.

It will take a day or two to write it up clearly, but in a nut shell, it involves cutting into the wiring harness that goes to the climate control board, tapping +12V and ground, and splitting the L/Y wire (control board sense to to fan speed selector line 1), then hooking in a circuit using these 4 wires. The circuit consists of a couple of resistors and a solid state relay. If there is a large voltage difference between +12V and line 1 (indicating that the blower is running) on the input of the solid state relay, the output side of the relay shorts the sense line to the climate control board to ground. If the blower is off, there is no voltage drop, a pull up resistor pulls the sensor line high, and the compressor shuts off. I picked up most of the parts at Radio Shack so that it would be easy for others to replicate this. The solid state relay came from Digikey though.

 

[jdwk]

Nice job, I was thinking something along the same lines. Kind of glad someone else did the work. Once you post the write up, I'll see if I can simplify it at all.

 

[covertsa]

A very impressive thread, and a pretty good headache that comes with reading it all in one day. I have to scratch my head though, as I have very similar symptoms, AC Light goes off all by itself, hardest to get to come on with fan on 4, eventually it will come on and stay on. Playing with the fan switch between 2 and 3 makes it come on.

The upgraded circuit board solution seems a bit shaky to me as this is on a 2005 Mazda3, it should have a good circuit board already, unless I'm missing something. How is it possible that a car company maintained a design this poor for that long?

 

[pasadena_commut]

The upgraded circuit board solution seems a bit shaky to me as this is on a 2005 Mazda3, it should have a good circuit board already, unless I'm missing something.

Best ask in the Mazda3 forum. For all I know 3's might have a problem with similar symptoms but a completely different cause.

How is it possible that a car company maintained a design this poor for that long?

It happens all the time. One example, Honda's CVT transmissions were crap for many, many years, with the startup clutch going out or needing constant (expensive) maintenance, and pretty much all of them failing by 100K miles. BMW had similar problems with the CVT in the Mini, but rather than letting it fester for years like Honda did they redesigned that clutch so that it could handle the required amount of torque without premature failure.

 

[Fresco]

I just finished installing a circuit that fixes this problem - solid green compressor light on all fan settings now. Whether it will hold up over time, well, only time will tell.

It will take a day or two to write it up clearly, but in a nut shell, it involves cutting into the wiring harness that goes to the climate control board, tapping +12V and ground, and splitting the L/Y wire (control board sense to to fan speed selector line 1), then hooking in a circuit using these 4 wires. The circuit consists of a couple of resistors and a solid state relay. If there is a large voltage difference between +12V and line 1 (indicating that the blower is running) on the input of the solid state relay, the output side of the relay shorts the sense line to the climate control board to ground. If the blower is off, there is no voltage drop, a pull up resistor pulls the sensor line high, and the compressor shuts off. I picked up most of the parts at Radio Shack so that it would be easy for others to replicate this. The solid state relay came from Digikey though.

ummmmm.......English Please lol

 

[pasadena_commut]

ummmmm.......English Please lol

Maybe this is clearer?

http://www.mazdas247.com/forum/showthread.php?123797885

It is still working nicely, by the way.

 

[mnkyboy]

Maybe this is clearer?

http://www.mazdas247.com/forum/showthread.php?123797885

It is still working nicely, by the way.

Is this the only fix that works?

 

[pasadena_commut]

Is this the only fix that works?

Equivalent fixes could be accomplished by other electronic circuits, but the place it would have to wired in would be the same. Otherwise, the fix is to buy the latest revision control unit.

There is a chance that changing a few components on the control board would also fix the problem. However the schematic in the manual did not give enough information to figure this out. To be sure somebody would have to do a careful side by side comparison of the final revision with an earlier one, and see what changed. If it's the IC, then forget about fixing an old one, because you'll never be able to source the part. Similarly, I doubt there are 3 people on this forum who have the right tools to replace surface mount components, and that is mostly what is on those boards. There are a few conventional "through hole" resistors and diodes - if by luck one of those was the component changed then an owner could probably repair the existing board.

 

[mnkyboy]

Equivalent fixes could be accomplished by other electronic circuits, but the place it would have to wired in would be the same. Otherwise, the fix is to buy the latest revision control unit.

There is a chance that changing a few components on the control board would also fix the problem. However the schematic in the manual did not give enough information to figure this out. To be sure somebody would have to do a careful side by side comparison of the final revision with an earlier one, and see what changed. If it's the IC, then forget about fixing an old one, because you'll never be able to source the part. Similarly, I doubt there are 3 people on this forum who have the right tools to replace surface mount components, and that is mostly what is on those boards. There are a few conventional "through hole" resistors and diodes - if by luck one of those was the component changed then an owner could probably repair the existing board.

Thanks but I meant a simpler fix. My #2 speed stopped working years ago, now #3 started flickering. Bad contacts?

 

[pasadena_commut]

Thanks but I meant a simpler fix. My #2 speed stopped working years ago, now #3 started flickering. Bad contacts?

Look, I really wish there was a "spray some PB blaster on it and smack it a few times" sort of fix, but the problem is with an improperly designed circuit board, which means the fix needs to be electronic too. There is lots of noise in this thread about bad contacts, and there clearly is a second issue where people see burned up contacts, but that problem is in addition to the flickering speed 2 & 3. Just to be clear, the contacts on my car were pristine, and I even disassembled and inspected the switch, and there was nothing wrong with it, yet it still had the flickering 2 & 3 problem. I carefully documented exactly what was going on voltage wise, earlier in this thread and it was clearly not a contact problem.

There is a simpler fix, but not a very good one. Look forward several posts and you will see that placing a power diode from blower line 1 to ground will also reenable the compressor at all speeds. The negatives, and these were too much for me, are that once that is done the fan will always run (if slowly) and that a pretty hefty diode is needed, because when the switch is in position 1 a lot of current will go through that diode. You could put a switch in line with it, but then you have a really ugly fix, where you want that second switch off in when the main fan selector is on 1 or off, and second switch on when the main is in positions 2 or 3. If you are willing to live with that, then all you need is a hefty power diode, some wire, and a switch. On the plus side this "fix" can cut in at the blower, so no need to pull out the center console to get to the wires behind the climate control unit.

 

[Weborific]

***UPDATE***
Hi. I'm the original poster of this "solution" and I'm surprised this thread is still going strong! Here's an update. The "fix" I posted about soldering the wires worked for 3 full years (almost to the day!) until my A/C light started flickering again just a few days ago. Since my wires are soldered, I doubted it could be the problem. Reading through this forum again, I came across a poster that mentioned that he cleaned the contacts on his resistor pack and that "helped" with his issue. I decided to give it a shot. So I removed my glove box, un-plugged and un-screwed the resistor pack, filed the contact faces clean, cleaned them with a contact cleaner (or isopropyl alcohol) and re-assembled. NO MORE FLICKERING! So, I believe this is a 2-part problem. Soldering DEFINITELY worked for me as it's been THREE years now and I didn't even inspect the connections this time around. Just went straight to cleaning the resistor pack contacts. So for those few that soldered but saw little improvement, DO BOTH and report back! My resistor pack was replaced 2 years ago, so the contacts have probably only now needed cleaning. Oh, and I also bent the 4 prongs SLIGHTLY downward to perhaps help make contact. Thanks for reading!

 

[pasadena_commut]

Folks, it just isn't normal for automotive wiring contacts to fail the way weborific describes. If it was everything electrical in the car would eventually go haywire, and/or all the high current connections would burn out once they built up some resistance. Weborific, do you by any chance live near the ocean? Salt air is hell on metal and might cause the problems you see.

 

[themodefanatic]

Just did this whole process on my 2002 Mazda Protege 5. EXCELLENT WRITE UP! WORKS GREAT! The process number 4 need a little more explanation like this,

*****4) You SHOULD un-clip the 2 cables that control the temperature and vent positions - THESE ARE UNDERNEATH THE DASH 1)LEFT SIDE BY GAS PEDAL, 2)PASSENGER SIDE UNDERNEATH GLOVEBOX.

 

[Weborific]

Folks, it just isn't normal for automotive wiring contacts to fail the way weborific describes. If it was everything electrical in the car would eventually go haywire, and/or all the high current connections would burn out once they built up some resistance. Weborific, do you by any chance live near the ocean? Salt air is hell on metal and might cause the problems you see.

Pasadena_Commut, I agree, it isn't normal AT ALL. But I am a very logical person. And logic tells me that if crimping the connectors tighter finally solved my issues for several weeks and soldering the wires solved the problem for THREE YEARS (and running), then there MUST be something to it. And that's all I can really say on the matter based on logic. I'm only sharing what I've observed and therefore MY results cannot be disputed. Your results may vary. Not to mention, there are PLENTY of people here that have soldered their connections as I have and reported success. So, these findings are factual and not fictional. Don't know what else to say on the matter. I know it just sounds so ridiculous that tightening the connections is a fix, but that's how it is on my end. Maybe by crimping (or soldering) there is a TINY difference in voltage that triggers the threshold that activates the compressor. I don't know...
Oh, and as for my update (just above) about cleaning the contacts to the resistor pack...that worked for just a few days. I will go back and crimp those connectors tighter this week. I have no doubt there's something else at play here, hence an updated climate control board from Mazda. Maybe I'll look into getting one, although I've read this hasn't solved the issue for everyone... Anybody have confirmation on whether the newer board works for sure and got a revision number? Thanks!

 

[Weborific]

Oh, and Pasadena, I saw your post for another solution and was VERY intrigued! Good stuff and great write-up! Of all the crazy stuff I've opened and tweaked or re-wired, I don't think I'd try your fix just yet. It seems too intimidating for me right now! hehehe. But I book-marked it and will either get a new board or try your fix. THANK YOU!!

 

[Weborific]

Just did this whole process on my 2002 Mazda Protege 5. EXCELLENT WRITE UP! WORKS GREAT! The process number 4 need a little more explanation like this,

*****4) You SHOULD un-clip the 2 cables that control the temperature and vent positions - THESE ARE UNDERNEATH THE DASH 1)LEFT SIDE BY GAS PEDAL, 2)PASSENGER SIDE UNDERNEATH GLOVEBOX.

Good call! Thanks! I guess I'm just not detailed enough! hahaha. Glad to see the fix works for you. Get back to us in a few days or weeks when you know FOR SURE that it actually worked. THANKS!!

 

[DeCaro]

The FAN works intermittently or the compressor light?

If the latter, get a piece of wire and with the switch in position 3 temporarily short from the L/Y wire at the resistor pack connector to ground (any bare metal on the chassis.) The A/C light should come on solid and the A/C should blow cold. That isn't a fix, but it tells you the problem is in the controller board and not the resistor pack or even the wiring. Look back a few posts to see why this works.

Sorry it took solong to reply... Thanks for the info. I managed to get a new replacement Switch. It works in all positions but 3 intermittently now. at first when I connected the new switch, it only worked on position 1 with a couple light tugs of the wires they all started working. I am taking that as a bad sign. The Controller board.... Do you know where this is located? If i follow the wires form the Switch, do they go directly to it, or?

Also, was anyone elses old AC switch discolored and Yellowed? Mine was. The new one is super white.