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Tech 2/ AC question


02suburbanZ71

Question

First off all my belt tensioner is bad, i can see it wiggle under idle, sometimes my AC loses blowing power and i was wondering if this is the problem because it blows cold.

 

My second question is i was going down the road and my cargo door indicator came on, this is the 4th time it happened and at the same time my doors unlocked/locked, but after i pulled over and shut the door again it stopped. If i had a tech 2 scan the vehicle (2002) what would they be able to diagnose, could they find out if the sensor for the door is bad or if there is a connectivity issue, and does anyone know the average cost to have a tech 2 at the dealer perform a full scan? Thanks everyone

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Blower motor has nothing to do with the a/c.. It is a simple fan motor. Speed will change with changes to battery voltage. If fan is on high, and you come to a stop, the fan will slow down because the alternator slows down, reducing its output due to speed change. Step on the gas, fan speeds back up as battery voltage increases due to alternator spinning faster. Completely normal and nothing to worry about.

 

If the door ajar warning comes on, something is setting that off. Are the cargo doors adjusted properly? Do they close tightly? I don't understand what you mean by unlocking and locking the doors. Are they doing this on their own, with no input from you or passengers?

I was driving 45 with the air blasting then it didnt blow as hard - as if it was on the 2nd setting. Then later it got more power- new battery and voltage is good on the cluster.

 

The rear cargo door does close properly and are tight, i thought it might be an electrical issue because- the ac stopped blowing really hard, the doors unlocked/locked them self- the same time the- cargo AJAR light came on...

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That does sound like a tensioner. Its worth mentioning, I think that's one of the years where GM updated the drivebelt specs, going with a slightly shorter belt to reduce belt squeal. Glazing on the smooth side of the belt that drives the water pump is a common culprit. The last one I did for a squealing issue I got the old belt size and it continued squealing, until I got the updated shorter belt.

 

I doubt that has anything to do with your ac. The belt would have to slip on the grooved side, and that would generate a great deal of heat before it reduced the AC output much at all. In other words, it would destroy the belt pretty quickly if it were slipping enough to make a difference. Off hand I don't have any good ideas for what would cause the blower to slow down on its own, except for a failing blower motor.

 

The other problem is likely a door switch sticking. They are prone to that, and spraying with WD40 might help. They are also prone to corrosion on the contacts which isn't always easy to clean. They can be removed and tested with an ohmmeter pretty easily, and they're cheap enough if you find one that's unreliable.

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Sounds like the belt is slipping - your losing the alternator's output when the blower "slows down" . I'm guessing you have a new battery because the old one died. If the belt is old, replace the tensioner AND the belt.

 

Nothing is set in stone in the automotive world, and especially so with all the electronics these days. Before replacing anything, check the simple stuff first, especially the battery connections, since they've recently been touched (new battery). Check the tensioner as mentioned prior.

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That does sound like a tensioner. Its worth mentioning, I think that's one of the years where GM updated the drivebelt specs, going with a slightly shorter belt to reduce belt squeal. Glazing on the smooth side of the belt that drives the water pump is a common culprit. The last one I did for a squealing issue I got the old belt size and it continued squealing, until I got the updated shorter belt.

 

I doubt that has anything to do with your ac. The belt would have to slip on the grooved side, and that would generate a great deal of heat before it reduced the AC output much at all. In other words, it would destroy the belt pretty quickly if it were slipping enough to make a difference. Off hand I don't have any good ideas for what would cause the blower to slow down on its own, except for a failing blower motor.

 

The other problem is likely a door switch sticking. They are prone to that, and spraying with WD40 might help. They are also prone to corrosion on the contacts which isn't always easy to clean. They can be removed and tested with an ohmmeter pretty easily, and they're cheap enough if you find one that's unreliable.

Where is the door switch located on the cargo door to lubricate with WD40?

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I was driving 45 with the air blasting then it didnt blow as hard - as if it was on the 2nd setting. Then later it got more power- new battery and voltage is good on the cluster.

 

The rear cargo door does close properly and are tight, i thought it might be an electrical issue because- the ac stopped blowing really hard, the doors unlocked/locked them self- the same time the- cargo AJAR light came on...

 

If all that happened at the same time you may have an issue with power or ground on the pwr lock circuit. Do the cargo doors have power door lock switches? Open both doors fully and look around the door opening for either a bundle of wires going from body into the door, or a square plate with a bunch of copper or brass coloured contacts in it. If you have that plate on the body of the truck, there must be a compatible one on the door in the same location.

 

There may be a nearly completely broken wire in the bunch of wires that are going from body to door. You can try letting the truck idle, and go to the cargo doors, open them and grab the wires that go from truck body to door and push and pull them. What you are looking for is something to happen. If there is a bad connection or bad switch, it may trigger the pwr locks, and while they are being activated, they may draw enough power to reduce (actually use up) power from alternator, that will slow the fan down while that is happening. Doubt Tech2 will show anything. Next time you are out driving, try putting the a/c fan at the speed it was at when this all happened, and press and hold the lock button down for a few seconds, does the fan speed change, then return to normal when you let go of lock switch? You could also try pressing the pwr window button to close the window when the window is already closed to see it slow the fan down while you hold the switch. Do NOT hold either switch down for much more than a few seconds.

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Also thought of something while on way to doctors office just now. Does your truck have the auto lock feature? Can you change the behaviour of it? On mine I can set it to lock when put in gear, or lock at a low speed, and unlock when put in park, or when engine is shut off, and some others I think.

 

You may have a bad ground connection somewhere in that system. If the BCM thinks the truck is being put in park, it will unlock the doors. If the truck is not being put into park, but the BCM thought it was, as soon as the doors are unlocked, the BCM sees that you are doing 50mph and the doors are not locked, so it locks them. Take a look at how your truck is setup for auto locking, and maybe change that setting to see if the unlock/lock at 40mph still happens. If it does not happen anymore, then the issue will be in the circuit that was being used in the previous setting. For example, if you had it set to unlock the doors when put into park, and how it is set to unlock when engine is shut-off, there is likely a problem in the circuit that tells the BCM that the trans is being shifted to park.

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Also thought of something while on way to doctors office just now. Does your truck have the auto lock feature? Can you change the behaviour of it? On mine I can set it to lock when put in gear, or lock at a low speed, and unlock when put in park, or when engine is shut off, and some others I think.

 

You may have a bad ground connection somewhere in that system. If the BCM thinks the truck is being put in park, it will unlock the doors. If the truck is not being put into park, but the BCM thought it was, as soon as the doors are unlocked, the BCM sees that you are doing 50mph and the doors are not locked, so it locks them. Take a look at how your truck is setup for auto locking, and maybe change that setting to see if the unlock/lock at 40mph still happens. If it does not happen anymore, then the issue will be in the circuit that was being used in the previous setting. For example, if you had it set to unlock the doors when put into park, and how it is set to unlock when engine is shut-off, there is likely a problem in the circuit that tells the BCM that the trans is being shifted to park.

Yes it has the auto lock feature. I'll drive it around see what happens then inspect it. Thanks for the help!

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I believe its easy to get to the belts and tensioner on that model. If you suspect the tensioner, put a wrench on it and slip the belt off. Then feel the range of movement on the spring - does it move smoothly, with even resistance? Does the pulley spin freely without feeling rough? Does it have no significant play? Its normal for the tensioner to move around a bit when the engine is running, as nothing is ever absolutely perfectly machined or lined up, and any play anywhere will wind up moving the one piece that can move - the tensioner.

 

In any case, it probably has nothing to do with your blower motor.

 

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I believe its easy to get to the belts and tensioner on that model. If you suspect the tensioner, put a wrench on it and slip the belt off. Then feel the range of movement on the spring - does it move smoothly, with even resistance? Does the pulley spin freely without feeling rough? Does it have no significant play? Its normal for the tensioner to move around a bit when the engine is running, as nothing is ever absolutely perfectly machined or lined up, and any play anywhere will wind up moving the one piece that can move - the tensioner.

 

In any case, it probably has nothing to do with your blower motor.

 

Its squeaking really bad and there is a massive amount of play in it just under idle conditions its hops all over the place. Could this cause slack which reduces AC power at idle?

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Blower motor has nothing to do with the a/c.. It is a simple fan motor. Speed will change with changes to battery voltage. If fan is on high, and you come to a stop, the fan will slow down because the alternator slows down, reducing its output due to speed change. Step on the gas, fan speeds back up as battery voltage increases due to alternator spinning faster. Completely normal and nothing to worry about.

 

If the door ajar warning comes on, something is setting that off. Are the cargo doors adjusted properly? Do they close tightly? I don't understand what you mean by unlocking and locking the doors. Are they doing this on their own, with no input from you or passengers?

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