Electrical Problem w/ A/C Heater Control - Air Conditioning Short?

[jrbueiz]

1999 Chevrolet Tahoe 4x4 LT - 4 Door

So I have been having a bit of a problem with my A/C and I think it may be related to where after installing a new battery the A/C goes kaput. This has happened to me twice already and I want to see if I can nail the problem before I go and spend another $200 on a new controller.

These two threads seem to describe what's happening to me but neither thread seem to come to a resolution:
THREAD #1
THREAD #2

This thread here sounds like a possible resolution to my problem; could be the explanation for the Control going out but what about the melted connects?:
THREAD #3

I believe the issue with the A/C Controller shorting out may have to do with toying with the battery (disconnect/connecting) with the A/C Controller in the on position. In the thread I mentioned above someone mentions the possibility of shorting out the microprocessors when when one does this. It could also have something to do with the blower motor resistor; as mentioned in other threads.

The one thing I cannot explain is why my connections are MELTED & BURNT. It affected my A/C Off-Hi connections and it has also affected my Passenger's Side brake light connection.

Maybe someone has some insight. Possibly to much voltage running through the system? Or could it be related to the disconnecting and connecting of the battery. I recently have been having issues with the Positive (+) side terminal post; it has been coming loose in turn disconnecting the battery. Before my latest A/C Controller went bad I had to constantly pop the hood to jiggle the terminal connection to get the Tahoe started; thus resulting in a constant disconnect and connect effect all while have the A/C Controller in the on position. I plan on applying some Locktite to the side post terminal to keep it in place.

Does Chevrolet make anything to fix bad connections like the ones I'm showing below?

Check out the pictures and tell me what you think. It's hot down here in Louisiana and I'm ready to have my A/C back.

A/C Control Off-Hi Knob:


Truck Side of A/C Off-Hi Control Connection (Burnt):


Original A/C Controller (Melted):


Replacement A/C Controller I purchased from the dealer (starting to melt):


Brake Light Connection Burnt:


Brake Light Connection Burnt Closeup:


Brake Light Connection NORMAL Closeup:



**FYI**
Climate Control Module:
AC Delco# 15-72547
GM# 09378805
UPC # 021625134475

[jrbueiz]

Does anyone have a picture of the blower motor resistor location?

How about the fan switch location? Is the fan switch the connection that I have that's MELTED?

[777stickman]

You didn't say what year Tahoe (or at least I can't find it). If it's a '99 is it old body or new body?

The plug you pictured is the plug for the fan control and did you use that same melted plug on the new controller?

As to the battery thing blowing out the controller and rear lights I don't think so, but I'm always learning new things on this forum.

If your Tahoe is a '99 and older model I may be able to point you towards some things to check..........Steve

[jrbueiz]

Originally Posted by 777stickman

You didn't say what year Tahoe (or at least I can't find it). If it's a '99 is it old body or new body?

The plug you pictured is the plug for the fan control and did you use that same melted plug on the new controller?

As to the battery thing blowing out the controller and rear lights I don't think so, but I'm always learning new things on this forum.

If your Tahoe is a '99 and older model I may be able to point you towards some things to check..........Steve

Steve...thanks for the reply.

The Tahoe is a 1999 LT 4x4 - OLD body style 4-Door.

I did use the same melted plug on the new controller. It worked well for approximately 4 months then it went out again.

Let me know what you think.

[jrbueiz]

Does anyone know if the GM dealers sell replacement connections to replace those that have burnt up/melted?

Not the entire harness, but more like something to splice in...in place of the bad harness?

[777stickman]

Glad to hear that you're going to replace that plug. Dealer should be able to get you one hopefully with all the wires in it so you can just splice it in.

From your pic's it appears that the pin that's getting hot is the brown wire which is the power feed from the HTR-AC fuse in the IP fuse block. This circuit is powered when the ignition switch is in the RUN position.

Here's what I would check. Using a digital multi-meter with the key in the OFF position make sure there is NO voltage on any of the wires in that plug. With the key in the RUN postion make sure there is voltage on the brown wire ONLY.

[jimvalako]

I'm having the problems with my HCV as well. (I bought 2 units) All the servos work but blows air on floor. The servo below the drivers side was not cycling to the full range so I switched it and it checked out ok.
I found that if I crossed the transistor the servo would work so I replaced it. Now if I turn the heat/air knob to cool/AC the board starts to heat up 130 degrees, if I turn it to AC it gets super hot where I cant touch it.

My question is the brown hot wire that goes into the unit supposed to be highvoltage? I show 10 volts

[777stickman]

Originally Posted by jimvalako

I'm having the problems with my HCV as well. (I bought 2 units) All the servos work but blows air on floor. The servo below the drivers side was not cycling to the full range so I switched it and it checked out ok.
I found that if I crossed the transistor the servo would work so I replaced it. Now if I turn the heat/air knob to cool/AC the board starts to heat up 130 degrees, if I turn it to AC it gets super hot where I cant touch it.

My question is the brown hot wire that goes into the unit supposed to be highvoltage? I show 10 volts

Just so we're on the same page. All the posts I've made in this thread are for '99 (old body style) and older (back to probably '96). So with that said:

My '98 service manual schematics show at least 2 brown power wires going into the HVAC control module at 2 different connectors. These wires are powered thru the HTR-AC fuse #12 25a in the instrument panel fuse block.

The HTR-AC fuse gets its power from one of five contacts in the ignition switch. This contact also powers 5-6 other fuses and supplies this power when the ign sw is in the run position only.

So, the voltage on the brown wires should read batt voltage coming out of the ign sw in the run position. Change the fuse just for grins and see what happens.

As far as the heat in the control panel (module). You've got some serious resistance trouble (resistance causes heat) either in the control panel or downstream from it (to some of the selected outputs).

[WHATDIDYOUBREAKNOW]

cars/trucks are built like shit problem #1

my old dodge would fry the heater fan selector about once a year

[jimvalako]

Originally Posted by 777stickman

Just so we're on the same page. All the posts I've made in this thread are for '99 (old body style) and older (back to probably '96). So with that said:

My '98 service manual schematics show at least 2 brown power wires going into the HVAC control module at 2 different connectors. These wires are powered thru the HTR-AC fuse #12 25a in the instrument panel fuse block.

The HTR-AC fuse gets its power from one of five contacts in the ignition switch. This contact also powers 5-6 other fuses and supplies this power when the ign sw is in the run position only.

So, the voltage on the brown wires should read batt voltage coming out of the ign sw in the run position. Change the fuse just for grins and see what happens.

As far as the heat in the control panel (module). You've got some serious resistance trouble (resistance causes heat) either in the control panel or downstream from it (to some of the selected outputs).

Thanks for the info sounds like ours are the same. I'm still struggling with my problem. Here's more info. When the tempeture knob is in the hot position the circuit board stays cool but the air blows out the floor. When I turn it to cool the board starts to heat up and the servo mid cabin moves the door and blows thru the upper vents. When I click it to A/C it gets extremely hot.