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Old 12-12-2010, 09:26 PM   #21 (permalink)
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So I did the measurements recommended in the prior thread and just to be sure used two different meters and got the same results.

First the continuity on the control module pic 1. between pins 9/12 and 10/12 with the recirculating knob pushed in and out. All combinations show OL on the monitor.
(Just to reiterate all other knobs function perfectly)

Second test the voltage on the harness pic 2. on pins 9 and 10 with the car key on. Here I did four separate tests, one with the console completely disconnected as in pic 1. then with the consoles two other plugs connected and the fan speed between 0-4.

All results were the same again, I got nothing on pin 9 and 11.55V on pin 10 with the only difference being that when the blower was on at any speed the voltage dropped to 11.35V

Since I had access to the harness I did a voltage test on all the pins and pin 8 was the only other one to show 11.55V

So what does this mean, could the recirculating actuator be fine ???
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Heater, blower failure-dscn0880.jpg   Heater, blower failure-dscn0879.jpg  
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Old 12-13-2010, 08:05 AM   #22 (permalink)
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Quote:
Second test the voltage on the harness pic 2. on pins 9 and 10 with the car key on. Here I did four separate tests, one with the console completely disconnected as in pic 1. then with the consoles two other plugs connected and the fan speed between 0-4.

All results were the same again, I got nothing on pin 9 and 11.55V on pin 10 with the only difference being that when the blower was on at any speed the voltage dropped to 11.35V

Since I had access to the harness I did a voltage test on all the pins and pin 8 was the only other one to show 11.55V
That looks good to me. The voltage on pin 10 (and pin 8) of the harness connector is consistent with the wiring diagram in post #19 above.

Quote:
First the continuity on the control module pic 1. between pins 9/12 and 10/12 with the recirculating knob pushed in and out. All combinations show OL on the monitor.
(Just to reiterate all other knobs function perfectly)
Just to be sure, I added pin numbers to your picture of the back of the control module. So there's no continuity between 9 and 12 and 10 and 12 in either position of the recirc switch. I would have expected some continuity, but perhaps the system inside works differently.

When the ignition is On, there's voltage at pin 10 of the harness connector, which according to the wiring diagram is coming through the actuator and it's rotary switch. Okay. A operational test of the actuator can be done, namely to carefully ground pin 10 at the harness connector. To do this, I'd recommend rigging up a wire with a 10 Amp fuse in series. This will protect you and the wiring in the event something is wrong. Put one end in pin 10, and connect the other end to ground. This should cause the actuator to run for one half cycle -- that is, move the recirc vane from where it is to the alternate position -- and then stop. At that point, there would be no voltage on pin 10, but there would be 12 V on pin 9. Grounding pin 9 would return the actuator to the original position. (It might be difficult to see, but if it's quiet where you're working, it should be possible to hear a very faint sound as the actuator motor runs. It runs 5 - 7 seconds.)

If this works, the problem is in the control module.
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Old 12-14-2010, 07:57 PM   #23 (permalink)
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So this is what the heater control looks like when you take the hammer to it pic1. Well not quite, but it really is a very intricate piece of equipment, the next few shots show the sequence of disassembly.

So finally we see the individual "bulbs" that light up the separate keys on the temp control. Here we also see a unique clear plastic bar which acts as a fiber optic "cable" taking the light from the small bulbs.

I was puzzled from the beginning why all the controls worked except the recirculating button/light and therefor the recirculating actuator. So I decided to to test the "bulbs" in pic 7 especially the corresponding recirculating one on the far right with a 9V battery pic 5. I figured the 9V battery should be enough to light up the bulb. Touching the wires to the back of circuit board did indeed show that the recirculating light was dead, all the other lights came on fine. Checked the soldering, it looked good, still no light. Went back and checked the other lights again, second light tested flickered and then went out, I thought my wire slipped so I reapplied and nothing. Now I have two lights out. I move one light over scratch the wires on the board, hold them there nothing, except this time I smell smoke, the very distinct circuit board smoke.
OK game over, at least I know what not to do the next time, what do they say about insanity; performing the same task over again and expecting a different result......
Went to the wrecker, pulled off another heater control, plugged everything in, all lights come on, all controls work INCLUDING THE STUBBORN RECIRCULATING ACTUATOR.. Very anticlimactic I know, at least I did not have to rip apart the dash or tear into the blower. (for now till the gaskets give) Hopefully others can laugh and learn from my mistake. If I ever loose any knobs I have lots to spare.
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Heater, blower failure-dscn0882.jpg   Heater, blower failure-dscn0884.jpg   Heater, blower failure-dscn0886.jpg   Heater, blower failure-dscn0887.jpg   Heater, blower failure-dscn0888.jpg  

Heater, blower failure-dscn0891.jpg   Heater, blower failure-dscn0894.jpg  
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Old 12-15-2010, 08:17 AM   #24 (permalink)
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Different approach (than in my post #22), but still a conclusion. Great!

Been a good run -- from isolating the strange cold air blast, to finding the recirc actuator and door, and finally isolating the actuator problem to the control module.

Looking at the last set of photos, I believe the six rectangular green and red "bulbs" are actually LEDs. (The three, round, green-capped lights are probably mini-incandescents.) The LEDs operate with not more than about 20 milliamps of current. Placing a battery directly across an LED's terminals, without any current limiting, will very likely cause it to burn out quickly.

I can see diodes, resistors, and two transistors on the printed circuit board, some, or all, of which might be there to limit/control the current going to the individual LEDs and bulbs. I can't think of any other purpose.

Were you able to identify what was burning?

Even if a bulb or LED is burned out, the associated switch should still work. So it would seem that there's a problem at the recirc. switch itself, either bad connections or the internal mechanism is faulty.

It is a learning experience that, as a result of your efforts (posting, providing photos, and persisting), might well help others in future.
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Old 12-15-2010, 02:19 PM   #25 (permalink)
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You are correct, the row of LED posts fit under the switches and light up when depressed, the two green incandescent bulbs fit into the clear plastic bar, you can see the indentations in pic. 5 this transmits the the light to the switches, blower knob and the "blue/red" heater adjustment bar.
I was not able to isolate and defects on the circuit board, I will look again with my loops.
So to summarize, the fault, other than the burned out LED on the original heater control unit must be on the circuit board itself because after the replacement controls were in place the original recirculating actuator worked just fine.

P.S
I also did the same tests on the new controls, conductivity between 9/12 and 10/12 and got the same OL result.
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Old 12-15-2010, 04:07 PM   #26 (permalink)
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Quote:
I also did the same tests on the new controls, conductivity between 9/12 and 10/12 and got the same OL result.
I'll have to get hold of a late-90s module, or at least the printed circuit board, and trace out the circuitry. It's possible that the ground line for the actuator circuit is not pin 12 (which goes to ground), but another pin. It could be pin 2, which is grounded through the fan switch, in which case the fan has to be at least on low speed for the recirc actuator to function. (On my 07, the actuator works as long as the ignition is On. The fan does not have to be running.)

But now you have heat and proper control, and that's what matters.
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Old 12-16-2010, 07:15 AM   #27 (permalink)
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Looked at the board, even with my loops I could not see any flaws, must be internally in a small component, I will try to take it apart some more.
Thanks for all the help along the way.
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