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another ATC problem

11K views 31 replies 6 participants last post by  cruzrkat 
#1 · (Edited)
Hello all and happy thanksgiving!
I am thankful for sites like this and all the great people who help others.
The reason I post today is figure out what is wrong with our 2000 300M. It started out with the Automatic Temperature Control,ATC display going off. The " slap the dash" would bring it back. Then I took the ATC apart and soldered the resistors as described on this site - the display works correctly. Now the blower only blows through the defroster vent, it won't switch to the side or floor vents. I did the diagnostic codes scan via the three button method and it came back at first with a code 24, so I ordered a mode door actuator (has not arrived yet). Just out of curiosity, I did the scan again, now it only shows a code 36. I tried two other ATC units(from pick and pull) and they also provide a code 36. Code 36 means " loss of communication" with the BCM.
So - where do I go from here? Any suggestions?
 
#2 ·
Disconnect the battery for 10 minutes to reset the BCM. Reconnect the battery and run the ATC diagnostics again via the 3 buttons. That should reset the ATC and get rid of the "Communication" code.
 
#4 ·
The ATC will always show the Communications error code after disconnecting it from the car wiring harness without disconnecting the battery first. If that was the case(good probability) then disconnecting the battery while working on the ATC will prevent that. The ATC has power to it at all times. You might notice when you open the drivers door that the aspirator motor in the ATC will run for a little bit even without the key in the ignition.
 
#5 ·
To be honest, this system has been so reliable over the years that anyone specializing in it would be on par with the Maytag repairman. I have done so few repairs on these, other than the display solder connections, that I didn't know. I did however note that the aspirator motor inlet grille does tend to collect lots of lint and debris. I cleaned mine out this past summer.

Waiting to hear if Laser3kw's problem is solved.
 
#6 ·
Mine just did this, but vice versa with the codes. Now I have to order an actuator. :lol

To be honest, this system has been so reliable over the years that anyone specializing in it would be on par with the Maytag repairman. I have done so few repairs on these, other than the display solder connections, that I didn't know. I did however note that the aspirator motor inlet grille does tend to collect lots of lint and debris. I cleaned mine out this past summer.

Waiting to hear if Laser3kw's problem is solved.
Don't forget to take apart the little fan and remove the crud, that gathers around the fan's pin, and regrease. I did that and now the ATC doesn't make a noise when I enter the car.
 
#9 ·
update:
I swapped in another ATC display and then ran the self check, code 36 came up. I pull the negative battery cable and let it sit for 30 minutes. That cleared the code 36, but the code 24 is still coming up. Next step will be to replace the mode door actuator. I'll probably do that next weekend.
As far as replacing it, I found a you tube video that shows the where its located and what has to be removed. My mechanic does not want to do the job, he said the console and a bunch of hoses have to be removed. I think he believes the blend door motor is what needs replaced.
Any advice on the job? Is it as simple as the video shows?
Thanks for the help so far.
 
#10 · (Edited)
It doesn't seem hard nor time consuming. Here are the steps from the FSM.
Code:
(1) Open hood and disconnect the negative battery cable remote terminal from the remote battery post
(2) Remove the left and right underpanel ducts.
(3) Remove the floor console
(4) Remove the center floor heat adaptor duct.
(5) Remove the rear seat heat forward adaptor duct.
(6) Loosen the center support bracket and pry rearward to gain access to the actuator.
(7) Remove the actuator retaining screws. Then pull the actuator straight down. 
[b]Upon removal, note the shaft position of the actuator, because the shaft on this motor is keyed.[/b] 
When installing a new actuator, its shaft must be positioned in the same location
(8) Remove the electrical connection on the actuator.
 
#11 ·
progress made
So I dove into the task of changing out the mode door actuator (MDA) with a new Mopar part. I started long version by dismantling the dash and console until I got the MDA out and installed the new one. Reassembled the dash parts, reconnected the battery, ran the self diagnostic.....
Frik'n code 24 came back . Guess what I said next. :poopoo:
So instead of the total dismantle, I did the internet video short version. Remove ATC bezel, remove radio, left duct, right duct, center duct. At that point I could remove and reinstall the MDA at will and watch its operation during self test. I also checked the vent rotor (the item that the MDA engages) and was able to switch the ducts from floor to defroster by hand with little effort.
I ran several self checks while watching the MDA.Sometimes it would rotate sometimes it would not. When it would rotate, it would turn clockwise (looking at the drive pinion) only, never turned counter clock wise. I would think, a self check test of a "servo", would include a sweep check, from clockwise a to b then counter clockwise b to a.
My next step is to get a known good ATC display and try that. Anyone have one for testing and purchase? If you are in the Rockford Il area drop me a PM.
If that isn't it maybe a junk yard BCM?:baseballbat:
Thanks for the help so far.
I hope to beat this yet!
 
#12 ·
I wonder if something was damaged when resoldering those contact points. I resoldered mine and have the 24 code. I disconnected the battery, left it that way overnight, and the next morning everything worked fine. However, hours later and the 24 code came back and the mode won't change. Tomorrow I'm making a yard run, so I'll let you know if a new ATC resolved the problem.
 
#13 · (Edited)
That is how I rationalized it. My thinking was the same about the soldering. Or possibly the 9 months of "dash slap" (to wake up the display) caused numerous voltage spikes that the microprocessor did not like. My hope is the BCM survived.
I am currently running with no MDA in place. I manually positioned the ducts so we have defrost and floor, so we can drive it. When I get the other ATC I will hook up both.
Another symptom appeared today. The ATC is going nuts'o. The fan switch was set to minimum, but the fan all of a sudden kicked up to high. At that point the switch would not control it. The air temperature also went to cool even thought it was set to 70º. The temperature also would not respond to commands. Yup I think the ATC has gone coo coo for coco puffs. I will try a different one any way.
keep us posted. I will do likewise.
 
#15 ·
Here's an update. I haven't replaced anything yet, but my mode has started working again. It was stuck on face, but while waiting in the car, during an errand, I did the self-testing. When it finished, I noticed it was stuck on defrost, so I did the testing again and all started working. I shall know when I look at it today, but I think the soldering did something.
 
#16 ·
coincidentally, I worked on mine today.
I stuck a new Mode Door Actuator as described earlier. I also got a "refurbished" ATC, just so I know I have a known good unit. Still have the code 24! I have been running without the MDA plugged in and still, the only code I get is 24. The situation has gotten worse, the temperature seems to not work properly. The temp seems to go cool until you turn it up to 80 then it gets warm. But there is no real pattern, sometimes it works. I had the cooling system checked out, filled and burped.
I am wondering if the Body Control Module (BCM) is bad. I have been disconnecting the battery while I do work on the ATC /MDA. I do not reattach it until everything is plugged back in.
Anyone have any input? I am at a impasse. Fix it, - dealer-$500 ~ $1000? Sell it, My wife needs a warm car, but she really likes this car.
 
#19 ·
found a flow chart for 'mode door feedback failure' which is code 24 stuff i think,and a schematic diagram for the ATC, in a 2003 LH body diagnostic manual should be helpful.don't have a DRBIII tool do i need one? 7 pages of things to try of things i don't fully understand .Is this the right path. oh ya i only removed the two lower heater ducts and center duct to access the mode door actuator to remove it so there's still a lot of things in the way to access wiring and connectors for testing.any help is appreciated thanks.
 
#20 · (Edited)
hi cruzrkat
I guess you could say mine is fixed. At first I had the disappearing display which was the resistors on the ATC cracking the solder joints. I resolder them and the display worked good. Then I started getting the code 24. I stuck a new Mopar MDA in it and it did not improve. I then got a "refurbished" ATC and put that in and still had problems.
I took it to a local independent shop and they used their computer to do diagnostics and made it do recalibration that way. They were stumped also. I ended up leaving the new MDA in and came to the conclusion the "refurbished" ATC was bad also. Stuck another junk yard ATC in, did a couple of recalibration and it seems to be fine now.
If I had to say what the main failure was, it would be the ATC went belly up. I just chased my tail a little when I got the refurbished one and unknowingly still had a ATC problem.
I would say if a shop with a computer can make the MDA work and recalibrate, I would look close at the ATC as the problem.
Hope this helps.
 
#21 · (Edited)
if your Interpid is similar to my 300m, remove the bezel and radio ad you can reach in and get to the screws way easier. You don't have to remove the console or other things. I found using a 1/4" drive ratchet, long extension, universal joint and 5/16 socket I could use one hand to guide the socket onto the screw and the other to loosen it. You have to work "blind" and by feel more than anything. I am a big guy - 6 ft and 230 lb and I was comfortable laying on the floor and reaching up and fiddling with the under dash stuff. I could watch the MDA move with the radio removed. You can see the tools and the radio in this picture. This and remove the ducts is all I did when I worked on mine.
 

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#24 · (Edited)
Minor trivia: If you don't have a 5/16" socket, an 8mm will work fine - in fact it's probably technically made for 8mm, but 5/16" is very close - actually slightly smaller so it fits snug (in fact if you have an 8mm hex that you have to apply a lot of torque to (like the tip of the stud on a corroded sway bar end link) and are afraid you might round off the hex, use a 6-pt. 5/16" for max. torque with least risk of rounding off). So yeah - either will work if you don't have one or the other.
 
#25 · (Edited)
thanks guys, i think I'll try a junkyard ATC I'll let you know if that solves the problem
If your are feeling really adventurous, get the MDA (mode door actuator). It gives you practice removing it and you don't have to worry about hurting anything. I unbolted the MDA and pulled it clear THEN un hooked the plug. Easier to see and less likely to break the plug trying to unclip it.
Also pull the fuse for the BCM while you work on it. That way you can do a fresh start up and recalibration of the ATC /MDA.
 
#26 ·
back from junkyard code 24 still mystifies after ATC from 300M installed. read voltage between mda pin #2 sensor ground and pin #4 5V supply during calibration mode and voltage varied between 4.8 and -7.8(?)is a negative reading even possible?even though gear on mda tried to move on some calibration attempts beginning to think its the actuator. btw i had to take the bezel off to change out the atc, from here its a piece of cake to remove radio and cd to get to mda thanks for the tip. time for a lagunitas IPA
 
#27 ·
Have you even considered connecting a replacement MDA but not installing it on the HVAC box and testing? If that works..then it's a good chance there's something in the HVAC unit that's causing the issue. Like something causing the Mode door to hang up.
 
#28 ·
I've been running the calibration mode with the mda plugged in but not bolted in place and watching to see if there's movement at the shaft. don't know if this causes misreadings by the body control module or not.with the mda off i can rotate the mode door (wheel) without much effort.now besides code 24 I'm getting code 33 also.Monday i'm back at pick and pull to get a mda and try that.ran out of time at the salvage yard or i would have picked one today thanks for the thoughts, how would i check to see if something is blocking the door . mirror and flashlight?
 
#29 ·
Are you testing with your original MDA?

How about outlining in detail what you've done so far....step by step.
 
#30 ·
basically this is what I've done; set ATC in diagnostic mode, got code 24 as result, removed mda from housing,left plug connected to mda then ran more calibrations to see if shaft on mda rotated any during calibrations. which it did sometimes. also checked movement of vent rotor by hand to see if there might be a rough spot in the rotation, seemed fine. next came junkyard ATC install, ran calibration code 24 again. disconnect battery 10 min. +, reconnect battery, check calibration code 24 again. calibration mode runs done with mda removed from housing but plugged in. then i unplugged mda and checked voltage reading between the 5V and sensor ground pins at connector and noted voltage variations during calibration run. didn't write down readings but somewhere between a high of 4.89 to a low of -7. something like that. that's about what I've done so far. i just bought the car two weeks ago knowing that the vents weren't switching.overall its a 2001 intrepid with 100k mileage very clean looks garage kept. replaced inner tie rod bushings and fixed power steering hose leak,and new front speakers last week.ordered lift supports front and back.after the mode door issue is fixed its on to a timing belt water pump job then tranny filter fluid change. antway thanks for the input on the mda problem,any insights are helpful
 
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