Intermittent HVAC operation
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Intermediate
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Intermittent HVAC operation
My car is a 2001 convertible. The HVAC control works sometimes and other times it doesn't. I had Dave at Corvette Illuminations check it out and he said it works fine. He even put it on his personal car and it worked fine. There is obviously a short somewhere; I have checked fuses and connectors and I am just about to pull my hair out. Does anybody have any clue what my problem might be?
Last edited by Larry Hargrove; Feb 10, 2021 at 11:08 AM. Reason: Wrong word
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
The first question is who’s Dave and is he a Tech ??...no idea what Corvette Illumination is ??...if your talking about your HVAC control module and he said the module is fine in his car maybe the module is OK...exactly what is happening ??...what makes you think there is a short ??...does the AC light come on when the AC is selected ??...pull the codes from the DIC and post what you see...this concern of yours can be a few things so there is NO magic bullet here unfortunately.
Last edited by C5 Diag; Feb 10, 2021 at 03:57 PM.
Melting Slicks
Joined: Jul 2004
Posts: 3,294
Likes: 480
From: Brea CA
Sounds like an ignition switch contact issue. As these cars age the contacts in the ignition switch get a carbon buildup from arcs as they are operated.
Have taken several apart and always find the same thing, black spots on the contacts. This buildup needs to be sanded off and it may be necessary to add a bit of bend to the contact arms so they make better contact.
If you are in SoCal I can help with this.
Gary
Have taken several apart and always find the same thing, black spots on the contacts. This buildup needs to be sanded off and it may be necessary to add a bit of bend to the contact arms so they make better contact.
If you are in SoCal I can help with this.
Gary
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Joined: Sep 2013
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From: Cape Coral, Florida
The only thing I can tell you is you would have to check the module’s power and grounds when it’s not working...don’t know what else to tell you...not knowing your electrical skill set I won’t elaborate on how to diagnose this !!
Thread Starter
Intermediate
Joined: Mar 2017
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Sounds like an ignition switch contact issue. As these cars age the contacts in the ignition switch get a carbon buildup from arcs as they are operated.
Have taken several apart and always find the same thing, black spots on the contacts. This buildup needs to be sanded off and it may be necessary to add a bit of bend to the contact arms so they make better contact.
If you are in SoCal I can help with this.
Gary
Have taken several apart and always find the same thing, black spots on the contacts. This buildup needs to be sanded off and it may be necessary to add a bit of bend to the contact arms so they make better contact.
If you are in SoCal I can help with this.
Gary
Racer
Joined: Jan 2021
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I don’t think an ignition switch would cause this issue. If the ignition switch was going bad I would say you’d have other major electrical issues.
Do you have access to another unit to test and try IN YOUR CAR? We first have to find out if it’s the car or the module. How long have you owned the car? Sometimes people try and fix the dim light issue and hack up the boards and cause major problems.
I did a quick and easy google search about corvette illuminations. Looks like dave does lighting repair. Did he do any work to your ac module? In order to help I would need a little more information.
Do you have access to another unit to test and try IN YOUR CAR? We first have to find out if it’s the car or the module. How long have you owned the car? Sometimes people try and fix the dim light issue and hack up the boards and cause major problems.
I did a quick and easy google search about corvette illuminations. Looks like dave does lighting repair. Did he do any work to your ac module? In order to help I would need a little more information.
Last edited by Chogan835; Feb 12, 2021 at 01:55 PM.
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Intermediate
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I replaced the ignition switch back in July so I am pretty sure that is not the problem. I have owned the car for almost 3 years. In that time I've not found any signs of previous electrical butchery. It had only 20k miles on it when I bought it. Dave went in and resoldered the 8 resistors that normally cause the lighting problem. After that he plugged the module on his own 'Vette and said that it worked perfectly. He seemed to be knowledgeable and and honest so I have no reason to doubt his word.
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Racer
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I replaced the ignition switch back in July so I am pretty sure that is not the problem. I have owned the car for almost 3 years. In that time I've not found any signs of previous electrical butchery. It had only 20k miles on it when I bought it. Dave went in and resoldered the 8 resistors that normally cause the lighting problem. After that he plugged the module on his own 'Vette and said that it worked perfectly. He seemed to be knowledgeable and and honest so I have no reason to doubt his word.
Racer
Joined: Aug 2019
Posts: 289
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From: Edinburgh, Scotland
If the unit has been out and in it doesn’t sound like it’ll be the connector.
As C5Diag is suggesting, the next steps would be testing whether the unit is getting power to it when it isn’t working.
I suspect it’ll mean needing to “back probe” the connector to see if power is or isn’t there. Also indeed checking the ground. I suspect it’s not a bad ground if it’s either completely fine or completely off though.
My gut is that the HVAC head isn’t right but a person would want to check incase power getting to the unit is cutting.
If you’re handy with a multi meter and could back probe the back of the connector after getting to the unit post back. C5Diag may hopefully guide you more.
As C5Diag is suggesting, the next steps would be testing whether the unit is getting power to it when it isn’t working.
I suspect it’ll mean needing to “back probe” the connector to see if power is or isn’t there. Also indeed checking the ground. I suspect it’s not a bad ground if it’s either completely fine or completely off though.
My gut is that the HVAC head isn’t right but a person would want to check incase power getting to the unit is cutting.
If you’re handy with a multi meter and could back probe the back of the connector after getting to the unit post back. C5Diag may hopefully guide you more.
Racer
Joined: Jan 2021
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I would just replace it. If it worked perfect before, then Dave “fixed” the backlights by disassembling and soldering the board, and now it doesn’t work........you already have the answer as to what went wrong. These things just don’t break on their own. Next time it doesn’t work take a video and send it to Dave.
also, those connectors back there can be very sensitive and cause problems if not pushed all the way in firmly.
also, those connectors back there can be very sensitive and cause problems if not pushed all the way in firmly.
Last edited by Chogan835; Feb 13, 2021 at 01:54 PM.
Racer
Joined: Aug 2019
Posts: 289
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From: Edinburgh, Scotland
I would just replace it. If it worked perfect before, then Dave “fixed” the backlights by disassembling and soldering the board, and now it doesn’t work........you already have the answer as to what went wrong. These things just don’t break on their own. Next time it doesn’t work take a video and send it to Dave.
also, those connectors back there can be very sensitive and cause problems if not pushed all the way in firmly.
also, those connectors back there can be very sensitive and cause problems if not pushed all the way in firmly.
Racer
Joined: Aug 2019
Posts: 289
Likes: 64
From: Edinburgh, Scotland
Racer
Joined: Jan 2021
Posts: 314
Likes: 61
let’s let the op explain further. He’s also not very clear if it’s just an illumination problem or a functional problem.
Racer
Joined: Aug 2019
Posts: 289
Likes: 64
From: Edinburgh, Scotland
The very first post explains that the unit was already exhibiting the fault when it was given to Corvette Illuminations.
“Playing up” is a figure of speech. Maybe one not used in US. We use it if something isn’t right. You’d say it was “playing up”.
When I said “went in” I was referring to opening up and going into the HVAC control head.
OP, good luck on getting it checked out. Seems sensible to try and check the power feed. A simple test light probing the orange wire should let you know what’s happening.
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Intermediate
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I finally got to work on this again and something happened that made me wonder. I had been working all day and had no luck at all. I was getting ready to call it quits for the day. I turned the ignition to off and the feature that let's the accessory like the radio stay on until you open the door kept the radio going kicked in. All of a sudden volume almost went off and the antenna started to go down. Then the volume and the antenna went back up and I saw that the hvac controller was working for the first all day. Does any of you have a clue as to whether any of these things could be my problem?