The compressor will not come on.I had the shop check it and he said it had a full charge he said he checked fuses but admitted to me he wasnt up on this kind of unit.It is the auto unit the heat works auto fan works fine. Really everything on the dash is 100% except a/c. I noticed the light blinked above the auto.Ive tried taking the ground off the battery.I dont want to wait till summer if i can help it. Any ideas? Thanks Dave

 

I would start by checking the low pressure cycling switch by jumping out the connector.

You can't really tell if it is full by checking the charge without the compressor running. You can check the static charge and get a ballpark idea if it has a charge, did he say what the pressure was? Anything over 50 lbs should close the cycling switch if it is working proper. 85-100 is a normal range.

If you have a flashing LED on the buttons, you should check the code in the control head. Follow this procedure and see what you have.

https://www.corvetteforum.com/techti...=193&TopicID=2

*** Here is another link with the info also with different layout. Maybe easier to read. **
http://www.corvetteactioncenter.com/...agnostic+Codes

 

Ok ill check this out. With temp under 40 degrees will it still kick on? Im stuck here in Va not Fla! But ill be down in Deltona for 3 weeks in Feb for Daytona race week,cant wait. Dave

 

with PColt,

except I'd reverse the diagnostics -- start with the code analysis via the AC control head.

Reason: the blinking LED indicates a fault which will prevent the AC compressor from engaging even if everything else is fine.

 

Go to the source of the problem,
start shopping around for a BCM. Thats where the circuit is completed/managed for the compressor clutch-coil. May be as simple as loose/dirty BCM plugs..

You can prove the BCM is bad with a DVM and some known proceedures in the FSM...Until you can prove the BCM is at fault, don't buy a replacement. Just locate one...

That BCM does a bunch of tricks...manages the clutch, the cabin blower, and completes the loop between programmer/control head/BCM. The BCM has specific test to determine if its faulty...this is in your FSM. The BCM runs about $75 for a clone...$125 for the real deal.

 

I have a similar situation I think... My car the lights have been flashing for some time, in fact I think they have been flashing since I bought the car. Fast forward to last week, and the clutch or bearing went bad on my compressor. I have another compressor on the way I found here on the forum, but last week as I was driving the car I went to turn the climate control off, and when I pushed the button the entire control panel 'died' for lack of a better word... No display, no lights nothing. I haven't checked any fuses in the fuse box in the car, but all the big fuses by the battery are fine.... I am guessing all this is related to the compressor taking a crap.... Hopefully this will just be a blown fuse and a compressor change... Anybody have any insight on this?

Didn't wan't to hijack your thread man, but I didn't feel the need to start a new thread for a similar problem.

 

Ok whats a BCM. I got DVm and FSM.

 

No problem

 

I think BCM might be a typo. I believe it should be ECM (engine control module) and the post world make perfect sense. It is directly involved in the A/C system with the activating the compressor and measuring pressures.

FYI - Your car has a CCM (central control module) which interfaces with many of the cars body functions like lights, dash display and security systems, etc. Some other earlier GM cars did have a BCM (body control module) which is similar to the CCM.

 

Thanks your proably right i see other mentions about the CCM.Is it odd that the only thing not working is the a/c? All other functions of the auto climate control work perfect. Do you think unplugging and cleaning contacts could do it? I guess its easy to try it.Dave

 

Cleaning contacts is a good thing to do if you know what the problem is and have localized the area. I don’t think you are there yet, I would not know what to tell you or what area you had in mind. I think you need to get a bit further in the troubleshooting phase to get a better handle on it.

Get the code and see what it is.
Check the cycling switch.
Check fuses # 1, 18 & 43

Check your FSM on pages about 8A-67 area to see what is involved for the A/C.
Lots of things have to happen to turn the compressor on. The cycling switch has to be closed, the high pressure sensor has to be in range, the ECM needs the A/C request from the programmer to energize the compressor relay which are some of the major things.

But since you are getting a flashing LED on the control head, that may give you a big clue as to what area to look in.

 

Not a typo.

Blower
Control
Module

aka a/c power module or compressor control module or a/c control module

BCM.
Mounted in top of the evaporator in opt 68 cars. Controls power to the clutch, control head loop, and blower motor. Your FSM will describe the circuit that you seek...the compressor clutch is HOT all the time. In the BCM the ground path is completed allowing the green wire to the clutch to energize and create a magnetic field in the coil (clutch coil) and that pulls the clutch against the spinning compressor pulley. Viola..a/c.

No test that I am aware of for the BCM other than symptoms. I'm sure there is some ohms test but I've never seen it.

 

Insert foot in mouth. Not like you to make many errors but I thought you perhaps did. You caught me definitely with this acronym and I missed it completely.

My apologies on this one, charge on.

 

Thank you, but no worries...
I'm the worlds worst when it comes to the proper ID or part description...

I walked around for 15 years calling that thing the a/c power module...and argued with every parts counter guy between Houston and Los Angles when they couldn;t find it with MY tag...


I sometimes have to grab the FSM and look at the glossary to see what the hell somebody is talkin about !

I was kinda surprised when nobody picked up on this after the many threads on blowers running without keys or compressors that would not engage and so forth...almost always comes back to the "module".

Oh yeah...
to be sure of this, also check the diode in the clutch coil plug. Personally I think that diode is a waste of $.17 worth of good Japanese solid state electronics. Its there to protect the BCM and coil from power spikes/surge but the thing is, the only place that these spikes can originate from is the part that the diode protects...the BCM.

Even after threats of wire fires and smoke and car-b-ques...I chopped mine out after it caused me much aggrevation with a no a/c condition one chilly Texas day in August...snip...problem solved. I was warned by the a/c gurus.
That was 4 or 5 yrs ago and nothing has happened except the a/c runs everytime I turn it on. Look at that diode and test for power --> not <- inline. Both sides of the plug are hot, diode only -> one way.

snip snip.....ahhhhh
kinda like a vasectomy for an a/c wire harness...you'll want to play with it right after the proceedure to see if it still works..

 

Thanks

 

Ok got it.My list is getting longer,this week end replace power steering pump! After rock fishing. Looks to be alot of room between radiator and motor?

 

Ok got my headlights working now the a/c.. Just printed out the code chart and after getting the blinking auto light i held down the up/down arrows and got 00 then i pushed the button between the arrows and got a 09 it looks like this is low freon? Mechanic said freon was ok but! he also said he didnt know these a/cs. The code directions are a little confusing it says to use arrows to select desired code? Are my missing something? Dave

 

Not 100% on the a/c codes but you can test the gas charge by simply jumping the low pressure cut out switch. Turn a/c on, eng running, jump the switch. IF compressor runs its got a low charge. IF NOT, move on.
I'd at least pull the plugs on the BCM, reconnect and see if that did anything. You might test for power in the BCM and see if that green wire to the compressor clutch is hot. That should have a charge all the time.
!...that will FRY the coil instantly, and probably anything else in the system. This is NOT the typical a/c system with a magnetic clutch.

 

When you got the 00 (system faults) and pushed the button between the arrows you did it correct and got the code. There are only 10 codes associated with the 00. The other stuff is for diagnostics to tell you what is going on with the system. It can tell you what is requested is correct, and the proper movement like a blend door. That is a whole other discussion but you usually have to just read the info and go thru the motions (play with it). It will take some time, some functions are useful and some not. You are not missing anything, you just have to come up the learning curve a bit more on this.

If you are really low on Freon the cycling switch may not be closed or the high pressure sensor senses a low pressure. You should be able to jump out the pins in the cycling switch connector and see if the compressor starts. If it does, this would verify the electronics are working.
I would like to know what the static pressure is because that would tell us a lot. If it is too low, the high pressure sensor (that measures Freon pressure high and low) might inhibit the compressor from starting.

Different amounts of Freon are used in different cars, but the pressures operate in a basic window across the board. This is regardless of whether you know the electronics of the system or not. I think the information from you A/C mechanic is pretty poor and making you have poor assumptions and decisions.

If you get the compressor the start, then you probably need to add Freon.
Since you like to fix you own stuff, get a set of gauges. You can but a new set for $60. Then you will know what you are doing and learn a new skill and not rely on bad information from others. If the compressor starts and it cycles every 5 or 10 seconds, it is low on Freon.

****** Just realized you have a 93. Is guess you are still running R12. You can get a license to buy R12 (easy, over internet) and then you can get it from EBay. Do you know for sure what you have?

 

All indications are it has never been changed to 34.I pulled negative cable and reconected it put a/c on high and watched clutch go on and off 4 times then stop. Checked and its blinking again code 9. My mechanic is ok with some things but a corvette is not one of them.I had him do trans,rear end,plugs and inspection this car was sitting for at least 4 yrs. I will try your suggestions this week end. Thanks and i hope its nice in Feb when i head to Daytona. Dave