A/C Diagnoses Help
Thread Starter
Instructor
Joined: Oct 2004
Posts: 202
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From: OKC Ok
A/C Diagnoses Help
I searched some in the forums, but was having trouble finding someone with the exact same symptoms as my situation (unless I missed it), so thought I would ask here. I'm trying to figure out what the cause of my Air Condition problem may be. I'm not very familiar with A/C systems in general so taking a stab at this with a blind eye. I'm attempting to save some money by repairing this on my own.
Here's a basic summary of what is happening: The A/C recently started not blowing air as much about a month ago roughly. It has been working intermittently since. When it did work, it did seem to blow nice cold air vs hot air, so I'm figuring I should be good on R12 refrigerant. Now, it seems to have quit blowing air the majority of the time. Occasionally it will start blowing again after I've driven for a bit, but seems to only push out very minimal air (as if I have it on a low setting, when in reality I have it on high/max on 10)...
Do you guys/gals have any thoughts on what the cause may be? Any help would be greatly appreciated.
Here's a basic summary of what is happening: The A/C recently started not blowing air as much about a month ago roughly. It has been working intermittently since. When it did work, it did seem to blow nice cold air vs hot air, so I'm figuring I should be good on R12 refrigerant. Now, it seems to have quit blowing air the majority of the time. Occasionally it will start blowing again after I've driven for a bit, but seems to only push out very minimal air (as if I have it on a low setting, when in reality I have it on high/max on 10)...
Do you guys/gals have any thoughts on what the cause may be? Any help would be greatly appreciated.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
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From: San Diego, Ca
Electronic Air uses a Module that amplifies low voltage inputs to control the speed of the Blower Motor. First verify that the Blower is capable of producing what it once did by jumpering it directly to the battery and at the same time, make sure it isn't dropping volts at the connector by looking for melted wires or discoloration. If it blows strong when jumpered and there's nothing amiss with the connector, locate the Module on the top left side of the Evaporator Case. The Brown wire is the low voltage input and whatever is hot at the Blower (either Purple or Black/Red) is the output. At Blower 1, the input should be 2.5 volts and the output 4 volts. At Blower 10, the input should be about 6 volts and the output 12 volts. If it has the correct input and the output is wrong, it needs a new Module. If the inputs are wrong, it either needs a Programmer or Dash Controls - further diagnosis will depend on the year.
Pro
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Here's a basic summary of what is happening: The A/C recently started not blowing air as much about a month ago roughly. It has been working intermittently since. When it did work, it did seem to blow nice cold air vs hot air, so I'm figuring I should be good on R12 refrigerant.
If you get 00, you have no fault codes, 09 means low on freon.
All this off course if you have the electronic version (C68).
Thread Starter
Instructor
Joined: Oct 2004
Posts: 202
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From: OKC Ok
Electronic Air uses a Module that amplifies low voltage inputs to control the speed of the Blower Motor. First verify that the Blower is capable of producing what it once did by jumpering it directly to the battery and at the same time, make sure it isn't dropping volts at the connector by looking for melted wires or discoloration. If it blows strong when jumpered and there's nothing amiss with the connector, locate the Module on the top left side of the Evaporator Case. The Brown wire is the low voltage input and whatever is hot at the Blower (either Purple or Black/Red) is the output. At Blower 1, the input should be 2.5 volts and the output 4 volts. At Blower 10, the input should be about 6 volts and the output 12 volts. If it has the correct input and the output is wrong, it needs a new Module. If the inputs are wrong, it either needs a Programmer or Dash Controls - further diagnosis will depend on the year.
.Oh, also, the year of my car is a 91 with electronic AC control.
Thanks vette079, I will try this tomorrow as well.
Last edited by DavesC4; Sep 19, 2009 at 03:24 AM. Reason: Adding year of car...
Thread Starter
Instructor
Joined: Oct 2004
Posts: 202
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From: OKC Ok
... I've been putting off buying one for a long time. I'll probably buy one in the near future as I can see how it would have been very handy in the past, present, and future, lol.Thanks again vette079, I'll report back with results tomorrow.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
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From: San Diego, Ca
There are no trouble codes for the Blower Motor or Blower Module and the only Codes that might effect Blower Speed would be an open or short of the Inside or Outside Temp Sensors. If the information from either sensor is garbage, you would need to know how to interpret it - but covering the basics first is far easier. Also, the inputs from those Sensors are ignored at Max - Heat or A/C - so at Auto 60 or 90, the Blower should be giving all it's got and not slowing down.
The Blower Motor is on the Passenger side Firewall - usually a hub or the motor housing which is a round tube protrudes into the engine compartment. Moving to the left, looking forward, is the Evaporator Housing. A rectangular box, it juts out into the engine compartment about a foot. On the top left side - again looking forward - is the Blower Module.
The Blower Motor is on the Passenger side Firewall - usually a hub or the motor housing which is a round tube protrudes into the engine compartment. Moving to the left, looking forward, is the Evaporator Housing. A rectangular box, it juts out into the engine compartment about a foot. On the top left side - again looking forward - is the Blower Module.
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Pro
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The info from Suncr is very helpful as well, I didn´t know that there were no codes for the previous mentioned problems... could have known if I´d read the FSM a little more perhaps...
Safety Car
Joined: Oct 2008
Posts: 4,689
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From: Yucaipa CA
Might not be a bad idea for me as well to check out, not that I have problems with mine, but to prevent them in the future.
The info from Suncr is very helpful as well, I didn´t know that there were no codes for the previous mentioned problems... could have known if I´d read the FSM a little more perhaps...
The info from Suncr is very helpful as well, I didn´t know that there were no codes for the previous mentioned problems... could have known if I´d read the FSM a little more perhaps...
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
GM uses/glues a foam filter on the inlet side of the Evaporator and when the Evaporator leaks, compressor oil destroys the filter and makes a gooey mess. If you find that, have it leaked checked. Unfortunately, it's extremely difficult to view the inlet side without removing half of the case - so I'd jumper the blower directly to the battery first.