Blower control module trouble

[Ronnie]

1 hour ago, LittleRed said:

I don't know where that leaves us.

We're getting nowhere with theory so I decided to do some hands on testing. Without starting the car and with the fog lights off,  I turned the key to run and let the brake pump run till it stopped and turned the key off. Then I connected my meter to ground and the purple wire going to the blower motor.

 

I turned the key back on and selected the climate control screen on the CRT. Below are the readings I got.

 

Ambient temp in my garage was 73* It appears when testing in AUTO mode that the fan speed voltage is being determined by readings from all the sensors such as ambient temp sensor,  sun load sensor, etc. My car was in the garage. I suspect the blower voltage would go to full battery voltage if the car was outside on a hot day in full sun when the temp was set to maxcool.

 

ECONj mode fan speeds:

Low speed= 4.16 volts

Hi speed= 10.29 volts

Auto= 5.36 volts

 

AUTO mode temp settings:

75* (default after battery disconnect switch closed)= 5.38 volts

65*= 7.94 volts

maxcool=8.64 volts

 

(now I went the other direction for heat)

80*= 6.13 volts

85*= 8.86 volts

maxheat= 8.64 volts <- actual voltage. not a typo. odd that voltage dropped on maxheat.

 

 

[LittleRed]

2seater and Ronnie you are both pointing to the same place, the control module, as I suspected. I hate to think that I am out $140 (because the part is not returnable but that seems to be where I am heading). I deeply appreciate all your assistance with this. If you have any more thoughts or suggestions, I am open to any and all.

[Padgett]

Not sure how PWM got in here is on later cas. Blower module is an SCR, essentially a variable resistor. I usually check with diagnostics and just jumper the blow fan to the 12v input to check. Believe I bought my last one from Jim Finn.

[LittleRed]

Ronnie, thanks so much for doing the "field" test on this. I am away from the car right now but when I get back to it I will have to duplicate your tests and see what my results are. It is odd that the max heat and max cool numbers are where they are. I had been doing my tests with max cool. I wonder what the econ numbers would be. It's perplexing to be sure.

[2seater]

Since Ronnie's tests were with the engine not running, somewhat lower voltages would be expected, especially over time. I do not know what the GM engineers have designed into the system, but I do know that I, and others, have commented on the unobtrusive nature of the climate control. I run mine in ECON a lot, even when temperatures really need A/C, but I don't use it for short trips. I notice the fan more at times like that as the system tries to bring down temperature using only airflow to accomplish it. I think they did a good job of using the best combinations when in full auto mode and staying in the background when doing so.

[Ronnie]

28 minutes ago, 2seater said:

I, and others, have commented on the unobtrusive nature of the climate control.

One thing I noticed in doing the tests is the blower seems to be louder under the hood than it is inside the car.  Maybe that is because the air was coming out the defrost and dash vents. I assume that is because there was no vacuum to operated the doors and such since the engine hadn't been started in a few days.

 

Not being started might account for low voltage readings as well. Battery voltage was 11.7 when I started. As you say it drops with the key on - engine off but it didn't take long to do the tests. If I had thought about it I would have put a second meter just on the battery to see how much it dropped while doing the tests.

[LittleRed]

For me, there is a difference between getting something to work and getting it fixed. I have accomplished the latter but not the former. In the past few months I have done everything I could think of to solve the problem of no "HI" speed blower. I hooked it up to oscilloscope to check the signals, I ordered a new control module, I took readings everywhere I could (I have 9.5 volts going to the control module from the AC programmer but only 3.6 volts to the blower motor. Today I took the other control module apart and everything looked good. I then hooked it up so I could run tests on it with the power on. In my testing I disconnected the ground wire from the "4" connector and the blower motor went to "HI" speed. I did some more testing and it worked in all settings. I then removed the ground connector from the housing and plugged it into my new unit and it worked with that one too. The only reason I can think of for this happening is that in the redesign of the control module a change was made that was not backward compatible to the Reatta. I share all this because some of you might be facing the same issue I was and are looking for a solution. Again, I don't know why it works, I just know it does. So take that for what it is worth and have a great day!