1990 L98 ac questions
Thread Starter
Intermediate
Joined: Aug 2012
Posts: 37
Likes: 0
From: Jersey Shore Pa
1990 L98 ac questions
I'm sure the answer is here but I can't find. It's blowing hot air. Showed code 09 low freon. Hooked up gauges. Static presure is 120 on high and low side and same with engine running. Compressor not engaging. I direct wired compressor to battery and it engages. When engaged pressure drops to 40 on low side and 240 high. Disconnect compressor from battery and it all goes back to 120. Freon isn't low. Any help is appreciated
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
If code 09 sets, the compressor clutch is disabled.
You need to disconnect the negative battery cable
to clear the code stored in the HVAC Programmer.
When you reconnect the battery, the Progammer
recalibrates the blend door which takes about 30 seconds.
When its done, the blower motor turns on.
09 indicates the compressor clutch is cycling to many
times with in a certain amount of time.
You need to disconnect the negative battery cable
to clear the code stored in the HVAC Programmer.
When you reconnect the battery, the Progammer
recalibrates the blend door which takes about 30 seconds.
When its done, the blower motor turns on.
09 indicates the compressor clutch is cycling to many
times with in a certain amount of time.
Last edited by Hooked on Vettes; Jun 22, 2013 at 08:30 PM.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
If it continues after you've cleared the Code, there might be a faulty Pressure Sensor or Low Pressure Switch. Ohm out the Low Pressure Contacts. Should be closed with 120 psi static. You'll need a Scanner for the Pressure Sensor, but it should show about 1.2 volts and that voltage needs to rise when the compressor engages. Otherwise, if there's no Codes and it doesn't engage, try a new Relay.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
A couple of quick checks.
In the static condition, check the resistance of the low pressure switch, it should be closed.
You can also jump out to connector for the low pressure switch and see if the compressor starts and system comes alive.
This can give you a feel if the switch is bad.
I would also follow procedure and reset the system as Hooked suggested.
In the static condition, check the resistance of the low pressure switch, it should be closed.
You can also jump out to connector for the low pressure switch and see if the compressor starts and system comes alive.
This can give you a feel if the switch is bad.
I would also follow procedure and reset the system as Hooked suggested.
Melting Slicks
Joined: Apr 2012
Posts: 3,364
Likes: 100
From: IOWA!!!
I'm sure the answer is here but I can't find. It's blowing hot air. Showed code 09 low freon. Hooked up gauges. Static presure is 120 on high and low side and same with engine running. Compressor not engaging. I direct wired compressor to battery and it engages. When engaged pressure drops to 40 on low side and 240 high. Disconnect compressor from battery and it all goes back to 120. Freon isn't low. Any help is appreciated
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
No AC expert for sure, but the static pressure of 120 seems really high unless the ambient temperature was really hot, like 90 to 100 degrees. Just going from memory, it seems like it should be about 70 pounds on a 70 degree day. Something like 84 on an 80 degree day. When you got the compressor going, did it start to cool air?
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Thread Starter
Intermediate
Joined: Aug 2012
Posts: 37
Likes: 0
From: Jersey Shore Pa
I appreciate all the advice. Just to update. I pulled the ctsy and radio fuses as well as disconnected negative terminal in order to clear the hvac programmer. Started the engine, put on max ac. With multimeter I checked voltage at hi pressure switch. 13.2 volts. Followed wire to low pressure switch, also 13 volts. This leads to dark blue wire at compressor. It also has 13 volts. Compressor doesn't engage. If I run wire from battery directly to compressor, it engages and I get 45 at the vents. I also did ohm test. Hi pressure was 0.00. Connector at compressor was 0.00. Low pressure switch was driving the meter crazy. All kinds of numbers flashed and then stopped at 1.
I'm going to try a new low pressure switch. For $10 it's worth a try. If the switch is bad I can't understand how I have voltage at the compressor.
I'm going to try a new low pressure switch. For $10 it's worth a try. If the switch is bad I can't understand how I have voltage at the compressor.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
I appreciate all the advice. Just to update. I pulled the ctsy and radio fuses as well as disconnected negative terminal in order to clear the hvac programmer. Started the engine, put on max ac. With multimeter I checked voltage at hi pressure switch. 13.2 volts. Followed wire to low pressure switch, also 13 volts. This leads to dark blue wire at compressor. It also has 13 volts. Compressor doesn't engage. If I run wire from battery directly to compressor, it engages and I get 45 at the vents. I also did ohm test. Hi pressure was 0.00. Connector at compressor was 0.00. Low pressure switch was driving the meter crazy. All kinds of numbers flashed and then stopped at 1.
I'm going to try a new low pressure switch. For $10 it's worth a try. If the switch is bad I can't understand how I have voltage at the compressor.
I'm going to try a new low pressure switch. For $10 it's worth a try. If the switch is bad I can't understand how I have voltage at the compressor.