Serious HVAC problems

My HVAC is REALLY acting up dims alot on me and I need to tap it, and today it went to -125 degrees and was making a super high frequency beep. It proceeded to go to -85 but it did that for hours. Got in after work and it fixed itself. any ideas?

See if it does it again...

As for the dimming, do a search on this board. The dimming is a well known problem that you can fix by pulling the HVAC control head and re-flowing the solder joints, the write up includes instructions.

Albertj

Albert is right about this being a BIG problem... If the actual AIR is running okay, then you probably just have to fix the climate control head.

So, I go to lunch today. Had the A/C crankin (it's 98* right now). Anywho, get to a stop light, it's ice cold now so I tried turning the blower down, no dice. It won't go any lower than 4 bars, but it goes higher. I decided to check the function of everything else. It goes to panel, goes to floor, goes to defrost, and goes to blend. It still changes temps no problem. So I get back to work. I hit the OFF button. The control panel goes off, but the blower motor doesn't......I shut the car off, the blower motor is still blowing I had to pull the backseat and remove the fuse so the battery wouldn't die. I'm hoping that maybe it's just the resistor again, but last time I could still turn it off........

Abaddon wrote:

So, I go to lunch today. Had the A/C crankin (it's 98* right now). Anywho, get to a stop light, it's ice cold now so I tried turning the blower down, no dice. It won't go any lower than 4 bars, but it goes higher. I decided to check the function of everything else. It goes to panel, goes to floor, goes to defrost, and goes to blend. It still changes temps no problem. So I get back to work. I hit the OFF button. The control panel goes off, but the blower motor doesn't......I shut the car off, the blower motor is still blowing I had to pull the backseat and remove the fuse so the battery wouldn't die. I'm hoping that maybe it's just the resistor again, but last time I could still turn it off........

Whoa, this is a new one.

Think you might have any wires crossed behind the dash? 98F is hot but probably not the cause of the failure.

Looking at wiring diagrams, I am thinking there's either a problem in the controller or a short in the wiring to it. The control head could have finally died.

I have to give this some thought.

Albertj

For some reason I think this is the blower control relay. Good luck with it. In this heat all you need is high anyway

Yeah it's a weird one eh? <-----------I literally looked like this when it happened. I called my buddy at the dealer (all he does is this kinda stuff). I told him what happened. He interrupted me before I finished and asked "does the blower motor stay on when you shut the car off?" I said yes. He immediately said it was the "resistor block". I trust him, so I ordered one from my old Buick dealer. Lucky for me, I still get employee pricing ($140).

I also studied the schematics for a while....what a mess. Funny thing is, there is no flow chart for "blower doesn't shut off" lol. It obviously has power, and if you look at the schematic, the Blower Motor Control Module (resistor block) controls the ground for the Blower Motor. Soooo, it kinda makes sense that it could FA!L the way it has.....

LOL at Deekster (high speed). There is no relay that controls the Blower Motor. Power to it is fed through the Blower Speed Feedback on the HVAC control head, goes into the Control Module, and to the Motor. As stated above, the BMCM grounds te Blower Motor......

I agree it's a weird one.

I assume by 'resistor', he means the blower control module? That would explain strange blower behavior, but I'm not sure it would explain the readout on the head not responding properly...

The little bit of guts in the ECC head is just for running the buttons, the lighting and the display. All the 'thinking' is done down in the programmer, and I hate to say it, but that is the one common denominator that would affect both the blower speed and the blower display... and also the DTC's or lack of them.
Of course, any kind of weird feedback could be happening from a single short or open, as we've learned from the other systems on the car...

HOLD IT!! Wait a sec.... Hmmm, I think I just figured out a nice, cheap, easy problem that could cause both these symptoms.

Scott, check the 10A blower fuse in the IP fuse block! I'll bet you a bottle of Beam that it's blown... (Don't you love my alliteration?)
If I'm right, I'll post the long explanation.
.

Make it a bottle of Old Grand Dad 114 and I'll go check it right now!

....the display IS reading properly, that's the weird part. The entire thing functions except for the motor stuck on.

EDIT! No soup for Eldo! I just went out and checked all of those lil 10A IP fuses related to the HVAC....they are all good.....

Abaddon wrote:

Make it a bottle of Old Grand Dad 114 and I'll go check it right now!

Hell, I have two of those! I didn't even know they made it any more...

Quote :

....the display IS reading properly, that's the weird part. The entire thing functions except for the motor stuck on.

Oh, I thought you said that it wouldn't go below 4 bars.

Quote :

EDIT! No soup for Eldo! I just went out and checked all of those lil 10A IP fuses related to the HVAC....they are all good.....

RATS!! At least I saved myself the explanation of my theory - Yada-yada-yada...

(Not to mention, this thing is as overpriced as the MSM module )

Abaddon wrote:

Anywho, get to a stop light, it's ice cold now so I tried turning the blower down, no dice. It won't go any lower than 4 bars, but it goes higher.

So, just what is blown, bad , malfunctioning or whatever.????

I would like to know for future reference.!!

Y'all use acronym's and abbreviation's as though we all know what they mean.

OK, sorry, I read and re-read the above. The Resistor Block is bad. Is that the same as the ????????

Abbadon Quote "the Blower Motor Control Module (resistor block) controls the ground
for the Blower Motor" Quote Abbadon.??????????????????????//
So it's a BMCM, any relation to the .............

How about a location and P/N or better yet, when you do get the part, could you take a pic and show where it goes. The reason I ask is I had an intermittent issue just like that and am waiting for the final death throws of this unit, part, acronym, abbreviation or whatever it is since it isn't a resistor like the older GM's had.

I have bought another HVAC Head Unit in preperation of it's death.

I don't know them all yet, and don't think i ever will.(Acronyms and abbreviations)
And just why the F---- does the Blower motor need it's own Control Module. Sometimes i just want to buy a 1970's something or other and avoid all these bloody control modules that do only one thing and cost a shitload of money. $140.00 for employee pricing, what about the rest of us dopes. We get used modules for that much.
Thanks

Eldo wrote:

Abaddon wrote:

Make it a bottle of Old Grand Dad 114 and I'll go check it right now!

Hell, I have two of those! I didn't even know they made it any more...

A party store a mile down the road orders it for me

Quote :

Oh, I thought you said that it wouldn't go below 4 bars

The display does, but the blower motor won't respond lower than 4 bars....

Rick, sorry for all the confusion. The Blower Motor Control Module does what the old style Resistor blocks did, just electronically. It receives a speed signal from the HVAC controller (display), and then controls the blower motor speed from there. The old style (as you know), literally had resistors on it to lower the voltage depending on switch position......This is why we think it's the module. If it's shorted to ground internally, it would keep the blower motor on with the ignition off because the motor has a constant B+.

As for "the rest of you dopes"....If ANYONE on here would like a dealer item at my cost, all you gotta do is ask
I'll even ship it to ya

Abaddon wrote:

Eldo wrote:

Abaddon wrote:

Make it a bottle of Old Grand Dad 114 and I'll go check it right now!

Hell, I have two of those! I didn't even know they made it any more...

A party store a mile down the road orders it for me

Quote :

Oh, I thought you said that it wouldn't go below 4 bars

The display does, but the blower motor won't respond lower than 4 bars....

Rick, sorry for all the confusion. The Blower Motor Control Module does what the old style Resistor blocks did, just electronically. It receives a speed signal from the HVAC controller (display), and then controls the blower motor speed from there. The old style (as you know), literally had resistors on it to lower the voltage depending on switch position......This is why we think it's the module. If it's shorted to ground internally, it would keep the blower motor on with the ignition off because the motor has a constant B+.

As for "the rest of you dopes"....If ANYONE on here would like a dealer item at my cost, all you gotta do is ask
I'll even ship it to ya

Thanks Scott.

Thanks for the explanation and the offer of employee cost on GM parts.
That is very generous of you, but watch out that you don't get bombarded by requests from us 'Dopes" and lose your benefit.
I would probably still have the benefit of employee pricing if the Dealer Didn't Shut Their Doors. I actually had a very good deal going with the Parts Manager that he would give me parts at his cost. It made it very easy to maintain a GM that way.
Rick

Abaddon wrote:

Eldo wrote:

Abaddon wrote:

Make it a bottle of Old Grand Dad 114 and I'll go check it right now!

Hell, I have two of those! I didn't even know they made it any more...

A party store a mile down the road orders it for me

I knew I liked this kid for some reason, even with his damned loud music...

Sorry for my age showing. No relays, you are right. Blower control module, or resistor block would be the correct thing.

good luck!

ALL fixed! Stupid lil expensive part and 10 minutes of labor!

what was it? and how`d you fix it.

The Blower Motor Control Module was it. If you guys want, I did take a few pics.....I spose I could do another write-up if ya want. It's a simple repair to do.

ohhh yes Abaddon, if you can post pics and a write up ,that may help many .I myself suffer from a similar problem.it just doesn't blow cold...aaaaaaaaauuugghhhh.

stan wrote:

ohhh yes Abaddon, if you can post pics and a write up ,that may help many .I myself suffer from a similar problem.it just doesn't blow cold...aaaaaaaaauuugghhhh.

If all your blowing is Hot Air then that control box is not your problem.

ohh no Rick, it doesn't blow hot air it just doesn't blow cold.The AC i filled a few weeks ago (it's still full) but the sucker doesn't blow cold....

Stan, regardless of the temperature, does the blower respond to the controls and turn off when the ignition is shut off?

Hi,Mark-yes when the ignition`s shut off, the AC is also off.What could it be? HVAC??

I was only clarifying, to keep you off a false trail. If your problem is only with air temp, then Abaddon's problem is not yours. I've been lucky in this department, but there are other threads that deal with the problems associated with A/C not getting cold... Try searching for other "A/C" "HVAC" or "air conditioning" threads. Also, please fill out your Signature file so folks know what year & engine you have.

Good luck!

yeah i thought this is a wrong thread sorry Mark.Yeah i know my profile is still blank.

1999 white diamond dust,SC.