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Discussion Starter #1
The heat on my '96 was intermittent for awhile, now off permanently.

I ran the HVAC control unit recalibration, and it failed a couple of times with different combinations of flashing button lights. I ran both tests in various orders, so may have confused it, but safe to say it fails.

Cold air and A/C work, and redirecting air flow between floor, defrost, and face works.

So I suspect the blend door actuator. A good guess? Question is whether it's totally electrical (the recal fail) or whether that can be caused by some mechanical piece being stuck or a by bad motor?

Any recommended drawings or videos for this fix?

I haven't felt the heater hoses to see if they're hot going into the firewall, but will tonight.

It's getting cold here in the mornings!
 

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Discussion Starter #2
I should also mention that air comes through the vents even if the fan is turned completely off. Does this imply that the blend door is stuck or worn out, and not just the blend door actuator?
 

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Does your vehicle have dual heat/cold controls (for driver and passenger)? The blend door actuator is a good guess. If you have dual controls, then there will be two. They are reachable from under the driver's side of the dash. To be more certain, after you run the calibration by holding the top and bottom vertical buttons on the left, what codes is the control unit displaying? For example, codes 14 and 15 are displayed by top button blinks once, bottom button blinks 4 times, then pause, then top button blinks once, then bottom button blinks 5 times, then it repeats. The codes will help you isolate the problem.

Here are some codes:
10: Passed all tests
11: Mode Actuator did not reach defrost position
12: Mode Actuator did not reach panel position
13: Blend/Pass. Actuator did not reach cold stop
14: Blend Pass. Actuator did not reach heat stop
15: Evaporator Probe Open
16: Evaporator Probe Shorted
17: Driver Actuator did not reach cold stop
18: Zone/Driver actuator did not reach heat stop
19: Control head internal failure

When you say that air comes through he vents even if the fan is turned completely off, this should only happen while the vehicle is being driven (as air enters through the front of the vehicle) if the recirc button is not set on, which is what it defaults to every time you start the car.
 

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Discussion Starter #4
Thanks for the reply. Yes, I have the dual heat control (as well as a separate rear A/C control on the ceiling in back, but that has never worked). There is a very slight amount of warm air coming out of the center passenger side vent (the second front the right). But all the other vents are cold.

After re-calibrate, the bottom button blinks 8 times, then the top button once. This sequence repeats several times, then the top two blink together and stay that way.

The list of codes is helpful. Is there somewhere a list of what flashing patterns correspond to the codes?

I went ahead and bought a blend door actuator just in case. Took off the panels under the steering wheel, and can see see two white modules on the right, arranged from front (driver) to back (towards the firewall). I assume the front one, is the ABS, and above that is a black module that looks like the blend door actuator I bought.

But the top bolt on the actuator appears to be up behind a metal bracket. How do you ever get that off?

The unit appears to connect directly to a series of black plastic gears, which I assume control the blend door itself. I may try manually turning the large gear to see if I can get heat.
 

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Discussion Starter #6
The list of codes is helpful. Is there somewhere a list of what flashing patterns correspond to the codes?

I went ahead and bought a blend door actuator just in case. Took off the panels under the steering wheel, and can see see two white modules on the right, arranged from front (driver) to back (towards the firewall). I assume the front one, is the ABS, and above that is a black module that looks like the blend door actuator I bought.

But the top bolt on the actuator appears to be up behind a metal bracket. How do you ever get that off?

The unit appears to connect directly to a series of black plastic gears, which I assume control the blend door itself. I may try manually turning the large gear to see if I can get heat.
UPDATE: I figured out how to get the codes and ran the calibration again:

CALIBRATION: Hold top left and bottom left buttons on the HVAC for five seconds. After all the tests are cycled through, the SECOND from the top button on the left flashes 8 TIMES, then the TOP button flashes once. This repeats over and over until I press the top button to end the test. After that, the top two buttons flash together continually.

THE CODES:
Using the method at https://www.allpar.com/fix/codes/index.html , I got my codes by watching the "Service Engine Soon" flashing. The codes were 12 (battery disconnected) and 55 (end of codes). "Battery disconnected" is because yesterday my battery went bad and I got a new one. 55 just means there are no more codes.

So that doesn't tell me anything about what the fault is.

P.S. For getting fault codes of other models/years, try https://www.allpar.com/fix/codes.html

Still don't know how to get the blend door actuator off.
 

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The code you are getting is 18. From the list

10: Passed all tests
11: Mode Actuator did not reach defrost position
12: Mode Actuator did not reach panel position
13: Blend/Pass. Actuator did not reach cold stop
14: Blend Pass. Actuator did not reach heat stop
15: Evaporator Probe Open
16: Evaporator Probe Shorted
17: Driver Actuator did not reach cold stop
18: Zone/Driver actuator did not reach heat stop
19: Control head internal failure

you can see that it is Zone/Driver actuator did not reach heat stop. You can try removing the actuator for the driver zone and comparing it to the one you purchased and if it's the same, replacing the actuator and running the calibration again to see if it fixed your problem. If the problem still persists with the new actuator then it may be a mechanical problem with the blend door itself or some issue with the hvac control.

Note that in the shop manual, the driver's zone actuator is referred to as "A/C Zone door actuator" and the passenger side is called "Blend Door Actuator" aka "Blend/Passenger Actuator. When you look up from under the steering area, if I recall correctly, the driver's actuator is slightly higher than the passenger actuator.
In order from lowest to highest, I believe the lowest one and easiest to reach is the passenger blend actuator followed by the driver's zone actuator and above that is the mode actuator which is incredibly difficult to access. I would avoid removing the passenger actuator if it is working ok. Hope this helps.
 

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Discussion Starter #8
So fault codes apparently can be read from both the flashing "Service Engine" light or the flashing HVAC button lights. But the flashing "Service Engine" light must be for other codes, not generated by the HVAC.


On my 1996 Grand Caravan, the actuators are positioned front (nearer driver) to back (nearer the firewall), with a third one above the front one and as you say, that one is incredibly hard to reach because it's partially behind a bracket. I ended up taking it to a mechanic who had done this before, and he said he could see some movement in the passenger actuator (the front one?) when moving the temp controls, so he left that alone and replaced the one further back toward the firewall, which controls the driver's side.

He had to do it twice because the shaft has to be positioned correctly to match the blend door or it won't calibrate. What that position is I'm not sure, it was in their shop manuals.

Heat works now.
 

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Interesting that he said the shaft has to be positioned correctly to match the blend door or it won't calibrate, because I don't recall seeing that in the Chrysler shop manuals. It makes sense though. Thanks for letting us know how you got it corrected and glad to hear that your heat is working now.
 
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