HVAC Problem - Any Advice?
Thread Starter
Tech Contributor
Joined: Dec 2003
Posts: 19,384
Likes: 87
From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
HVAC Problem - Any Advice?
Had a problem with the HVAC on the way home today.
The HVAC was working normally for most of the trip. On the way back it turned off and the ac light went out. When I try to reselect to on the ac light flashes but will not engage. I still seem to have heat coming from the vents.
Pulled the codes and I had a 99 HVAC - B1160H - Loss of Serial Data - VIN Not Received.
I've had a dead battery after the two month transit on the boat. I'm just recharging the battery now. I'm thinking a total hard reset of the computers by disconnecting the battery may help.
Anyone seen this and can offer any advice?
The HVAC was working normally for most of the trip. On the way back it turned off and the ac light went out. When I try to reselect to on the ac light flashes but will not engage. I still seem to have heat coming from the vents.
Pulled the codes and I had a 99 HVAC - B1160H - Loss of Serial Data - VIN Not Received.
I've had a dead battery after the two month transit on the boat. I'm just recharging the battery now. I'm thinking a total hard reset of the computers by disconnecting the battery may help.
Anyone seen this and can offer any advice?
Thread Starter
Tech Contributor
Joined: Dec 2003
Posts: 19,384
Likes: 87
From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
JC in XTC5 to the Rescue!
I worked my way through all the threads and I've answered the question.
Having been a "Vegas Hot House Flower" I cant say I've seen temperatures below about 40 very often. It hit 31 degrees here in England today and I had to use the heater probably for the first time in anger
JC in XTC5 thanks again for a great response to a previous post.
"Before jumping to conclusions that there is a serious problem, PCM or otherwise, this is normal operation for the Dual Zone unit depending on the external temp reading.
If the external temp is reading below ~38F the system will prevent the AC from coming on. When you hit the AC button in this condition, it will blink 3 times then turn off to indicate that the operation is not allowed. Similarly in warmer temps if the system is directing airflow to the defogger windshield vent the AC is automatically ON - if you try to turn the AC off by hitting the AC button it will blink 3 times and stay on.
The question is why are you hitting the AC button to heat? Just hit the AUTO button and set the desire temp. "
Having been a "Vegas Hot House Flower" I cant say I've seen temperatures below about 40 very often. It hit 31 degrees here in England today and I had to use the heater probably for the first time in anger
JC in XTC5 thanks again for a great response to a previous post.
"Before jumping to conclusions that there is a serious problem, PCM or otherwise, this is normal operation for the Dual Zone unit depending on the external temp reading.
If the external temp is reading below ~38F the system will prevent the AC from coming on. When you hit the AC button in this condition, it will blink 3 times then turn off to indicate that the operation is not allowed. Similarly in warmer temps if the system is directing airflow to the defogger windshield vent the AC is automatically ON - if you try to turn the AC off by hitting the AC button it will blink 3 times and stay on.
The question is why are you hitting the AC button to heat? Just hit the AUTO button and set the desire temp. "
