Hvac no comm...?
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Joined: Jul 2011
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From: Wauregan CT
Hvac no comm...?
Recent new battery...recent AC service, system found to be functioning properly and small amount of 134 added to top it off.
Blowing colder on pass side that drivers side which I understand is a common C5 issue with assorted possible cures.
I had read that clearing any HVAC codes and hearing the actuators subsequently reset themselves was a frequently suggested fix after connecting a new battery. But instead of a code I found NO COMM...which doesn't appear to be a clearable reading since it won't go away...I did try to no avail...obviously actuators did not react either
I can live with the unbalanced AC output, but in the interest of keeping my Vette in proper order I want to pursue a fix.
Any help is appreciated, and searching does churn up plenty of AC stuff...in fact enough to be confusing to my 64 year old brain...so if one of you AC hotshot would enlighten me a bit I'd be grateful.
Also note I get NO COMM from both LDCM & RDCM...could those 2 be interelated to the HVAC NO COMM perhaps
Thank You
Bob
Blowing colder on pass side that drivers side which I understand is a common C5 issue with assorted possible cures.
I had read that clearing any HVAC codes and hearing the actuators subsequently reset themselves was a frequently suggested fix after connecting a new battery. But instead of a code I found NO COMM...which doesn't appear to be a clearable reading since it won't go away...I did try to no avail...obviously actuators did not react either
I can live with the unbalanced AC output, but in the interest of keeping my Vette in proper order I want to pursue a fix.
Any help is appreciated, and searching does churn up plenty of AC stuff...in fact enough to be confusing to my 64 year old brain...so if one of you AC hotshot would enlighten me a bit I'd be grateful.
Also note I get NO COMM from both LDCM & RDCM...could those 2 be interelated to the HVAC NO COMM perhaps
Thank You
Bob
Tech Contributor
Joined: Jan 2007
Posts: 19,353
Likes: 1,126
From: Dyer, IN
Recent new battery...recent AC service, system found to be functioning properly and small amount of 134 added to top it off.
Blowing colder on pass side that drivers side which I understand is a common C5 issue with assorted possible cures.
I had read that clearing any HVAC codes and hearing the actuators subsequently reset themselves was a frequently suggested fix after connecting a new battery. But instead of a code I found NO COMM...which doesn't appear to be a clearable reading since it won't go away...I did try to no avail...obviously actuators did not react either
I can live with the unbalanced AC output, but in the interest of keeping my Vette in proper order I want to pursue a fix.
Any help is appreciated, and searching does churn up plenty of AC stuff...in fact enough to be confusing to my 64 year old brain...so if one of you AC hotshot would enlighten me a bit I'd be grateful.
Also note I get NO COMM from both LDCM & RDCM...could those 2 be interelated to the HVAC NO COMM perhaps
Thank You
Bob
Blowing colder on pass side that drivers side which I understand is a common C5 issue with assorted possible cures.
I had read that clearing any HVAC codes and hearing the actuators subsequently reset themselves was a frequently suggested fix after connecting a new battery. But instead of a code I found NO COMM...which doesn't appear to be a clearable reading since it won't go away...I did try to no avail...obviously actuators did not react either
I can live with the unbalanced AC output, but in the interest of keeping my Vette in proper order I want to pursue a fix.
Any help is appreciated, and searching does churn up plenty of AC stuff...in fact enough to be confusing to my 64 year old brain...so if one of you AC hotshot would enlighten me a bit I'd be grateful.
Also note I get NO COMM from both LDCM & RDCM...could those 2 be interelated to the HVAC NO COMM perhaps
Thank You
Bob
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Joined: Jul 2011
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From: Wauregan CT
Hi Mike,
Yes doors lock and windows work fine. The remote doorlock function is suddenly not working though...I rarely lock the car so didn't even notice this. My car doesn't have the dual climate system.
Bob
Yes doors lock and windows work fine. The remote doorlock function is suddenly not working though...I rarely lock the car so didn't even notice this. My car doesn't have the dual climate system.
Bob
Tech Contributor
Joined: Jan 2007
Posts: 19,353
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From: Dyer, IN
Ok. The manual A/C does not communicate over the class 2, thus...no comm. The DCM's are another problem entirely. Please post ALL codes.
Tech Contributor
Joined: Jan 2007
Posts: 19,353
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From: Dyer, IN
Ok, this suggest a few things are going on. Just curious, does your radio ever stop working, or the display just go off? Also, do you have F45, and has it been working normally?
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Tech Contributor
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From: Dyer, IN
Thread Starter
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Joined: Jul 2011
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From: Wauregan CT
Hi Mike,
I bought it one month ago. I do check codes and try to understand there meaning from the published lists available. I haven't had an actual problem in the running quality of the car itself except for this AC deal we are discussing.
Mike, you pointed out...The manual A/C does not communicate over the class 2, thus...no comm....does this suggest the manual HVAC will not generate a code when it's having a problem?
Thanks
Bob
I bought it one month ago. I do check codes and try to understand there meaning from the published lists available. I haven't had an actual problem in the running quality of the car itself except for this AC deal we are discussing.
Mike, you pointed out...The manual A/C does not communicate over the class 2, thus...no comm....does this suggest the manual HVAC will not generate a code when it's having a problem?
Thanks
Bob
Last edited by camburger; Sep 8, 2011 at 10:12 AM.
Racer
Joined: Feb 2004
Posts: 359
Likes: 7
From: St. Paul MN
Are you getting any other startup messages on the DIC like "Service Selective Ride Control", or any alerts if you try to exceed 80 mph?
If you pull your code list and it says "RTD NO COMM", it means the BCM is expecting to see the Real-Time Damping controller in the trunk, and it doesn't. If the car doesn't have the RTD F45 hardware, "38-RTD" should not even appear in the list. I would expect this to be true of the Auto-HVAC as well, no entry for manual HVAC.
Check the glove compartment for the list of RPO options the car was originally built with. Someone may have been monkeyin'. A Tech-II can add or remove options not originally ordered.
C5 RPO Code List
Todd
If you pull your code list and it says "RTD NO COMM", it means the BCM is expecting to see the Real-Time Damping controller in the trunk, and it doesn't. If the car doesn't have the RTD F45 hardware, "38-RTD" should not even appear in the list. I would expect this to be true of the Auto-HVAC as well, no entry for manual HVAC.
Check the glove compartment for the list of RPO options the car was originally built with. Someone may have been monkeyin'. A Tech-II can add or remove options not originally ordered.
C5 RPO Code List
Todd
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From: Wauregan CT
Hi Todd,
No messages over 80mph. In fact the car runs fine in every respect except the AC imbalance that I originally noted.
The rest of your info will need checking once I'm back home. ...is any of this selective ride or real time damping somehow connected to that HVAC NO COMM message and potentially to the AC matter?
Thanks for your input.
No messages over 80mph. In fact the car runs fine in every respect except the AC imbalance that I originally noted.
The rest of your info will need checking once I'm back home. ...is any of this selective ride or real time damping somehow connected to that HVAC NO COMM message and potentially to the AC matter?
Thanks for your input.
Last edited by camburger; Sep 9, 2011 at 08:52 AM.
Racer
Joined: Feb 2004
Posts: 359
Likes: 7
From: St. Paul MN
Bob,
RTD is not at all associated with HVAC, it's the NO COMM on three modules that got me going. I haven't seen "NO COMM" before unless an expected module is not being seen. My theory (a bit out there) is that you may have hardware for an automatic HVAC, but just the head-unit of a manual. The 2nd actuator isn't actually moving since the head unit isn't controlling it. http://forums.corvetteforum.com/c5-t...1998-vert.html does not have a "99-HVAC" reported with manual HVAC.
Bill' post #4 here also says there is just one actuator for the manual HVAC unit for hot/cold mix. It shouldn't blow significantly hotter/colder through the different vents. Have you measured the temps? Does it fully cycle hot-to-cold, just not as cold as expected?
Your first post indicated LDCM and RDCM "NO COMM"s, but are those not present now, or intermittent? In addition the SCM NO COMM (seat control) and RFA (key fob) issues would lead me to believe you also have OBD-2 bus problems. These are commonly caused by a loose serial data wire in the door accordians, or a shorted seat control module. Did you happen to have a battery drain issue to warrant replacing the battery?
Todd
RTD is not at all associated with HVAC, it's the NO COMM on three modules that got me going. I haven't seen "NO COMM" before unless an expected module is not being seen. My theory (a bit out there) is that you may have hardware for an automatic HVAC, but just the head-unit of a manual. The 2nd actuator isn't actually moving since the head unit isn't controlling it. http://forums.corvetteforum.com/c5-t...1998-vert.html does not have a "99-HVAC" reported with manual HVAC.
Bill' post #4 here also says there is just one actuator for the manual HVAC unit for hot/cold mix. It shouldn't blow significantly hotter/colder through the different vents. Have you measured the temps? Does it fully cycle hot-to-cold, just not as cold as expected?
Your first post indicated LDCM and RDCM "NO COMM"s, but are those not present now, or intermittent? In addition the SCM NO COMM (seat control) and RFA (key fob) issues would lead me to believe you also have OBD-2 bus problems. These are commonly caused by a loose serial data wire in the door accordians, or a shorted seat control module. Did you happen to have a battery drain issue to warrant replacing the battery?
Todd
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Posts: 19,353
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From: Dyer, IN
To the OP, you have to be very careful who you listen to on this forum. If you feel you have the expertise to troubleshoot the AC issue, PM me your email, and I will send you the service manual procedure.
Racer
Joined: Feb 2004
Posts: 359
Likes: 7
From: St. Paul MN
Yes Lucky, improbable. Just going by the codes provided.
How did you get to this determination about HVAC-99 "NO COMM"s being reported with a manual HVAC as being OK? This thread confirms that '99-HVAC' shouldn't even show up for 1998.
Lucky, not trying to be argumentative - I actually want to know. If the '97s do this but other years don't, I'd love to know. I respect your knowledge and expertise here, and would like to learn more about the C5s. The "be very careful who you listen to" is not very constructive.
Todd
The manual A/C does not communicate over the class 2, thus...no comm.
Mike, you pointed out...The manual A/C does not communicate over the class 2, thus...no comm....does this suggest the manual HVAC will not generate a code when it's having a problem?
Lucky, not trying to be argumentative - I actually want to know. If the '97s do this but other years don't, I'd love to know. I respect your knowledge and expertise here, and would like to learn more about the C5s. The "be very careful who you listen to" is not very constructive.
Todd
Tech Contributor
Joined: Jan 2007
Posts: 19,353
Likes: 1,126
From: Dyer, IN
This thread confirms that '99-HVAC' shouldn't even show up for 1998.[/QUOTE]
Again, I don't know the history(doubt the OP does either). I'm troubleshooting the issue, not the PCM.
Here's what is known. The OP has a working manual A/C system....with an issue. That being said, it is not possible to have manual control panel function with a automatic climate control A/C system....period.
When someone is searching for help, and you come up with a completely unfounded(not to mention impossible theory), it's bad advice......simple as that. I distance myself from topics discussed on this forum, which I do not have personal experience, expertise, or knowledge of exactly what is possible.........you should do the same.......otherwise, you just add to the problem..by creating confusion. Nothing personal, I just don't like BS information circulated.
