1988 Cadillac Brougham ECC Issue

Olds G's

Greasemonkey
Apr 6, 2020
119
43
CT
Hi all,
I've got my FIL's 1988 Cadillac Brougham (the RWD one) in quite fantastic condition. The one issue with it is the ECC head will not let me select a temp lower than 75 deg. I can select higher, just not lower. When in "Auto" the system does work as far as the fan ramping up and back down again when the selected temp is reached... so long as it is 75 or higher.

I connected my Snap-On Solus Pro up and noted that it showed:
Low A/C Press.... YES
A/C Request.......Yes
A/C Clutch...........Off

I figured that it may just be low on charge. I put 2 pounds virgin R12 in whilst jumping the Low A/C Press connector in order to get the clutch to engage (it did). The Solus Pro showed:
Low A/C Press.......No
A/C Request.........Yes
A/C Clutch..........On

Feeling the air conditioning lines, it sure did seem like everything was circulating as it should. When I went to select a lower temp than 75, I was still not able to. Higher, yes. So, still the same fault.

I disconnected the jumper and remade the connection to the low press switch and noted that the original fault remained. I still cannot select a temp lower than 75.
Low A/C Press......Yes
A/C Request.......Yes
A/C Clutch..........Off

End result here is that I know that I have good R12 and pressure at this point. So, do I go after the ECC control head, programmer, power module? I do have all the GM manuals including wiring. GM never discussed what to do when a selection of temp was not available. Basically the troubleshooting tree says "run the temp full hot and this should happen; run the temp full cold and that should happen but not what to do if one of those selections didn't operate.

Back probing connectors is next but I'm hoping someone has some good GM experience to guide me.

Thanks in advance,
Olds G's
 

303'505rollin

G-Body Guru
Sep 4, 2020
700
93
Colorado2newmexico
How bout a picture of that unit, I can't picture it right off the top of my head. Then I'm thinking that it maybe stuck in defrost and being electric won't switch over to AC till it does
 
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Olds G's

Greasemonkey
Thread starter
Apr 6, 2020
119
43
CT
Good morning 303'505rollin,

Yes, I'll provide a pic shortly. I can select between defrost and auto but no difference in ability to change temp setting lower. Higher yes, lower no. It does go into defrost mode and back to auto when selected rather than just an indication on the ECC.

I'll send pics in a few hours and thanks for the help.
 

Olds G's

Greasemonkey
Thread starter
Apr 6, 2020
119
43
CT
Good morning 303'505rollin,

Yes, I'll provide a pic shortly. I can select between defrost and auto but no difference in ability to change temp setting lower. Higher yes, lower no. It does go into defrost mode and back to auto when selected rather than just an indication on the ECC.

I'll send pics in a few hours and thanks for the help.
 

Attachments

  • Cadillac ECC 20220323_112954 (1).jpg
    Cadillac ECC 20220323_112954 (1).jpg
    1.3 MB · Views: 49
  • Cadillac ECC Back Face 20220323_124917.jpg
    Cadillac ECC Back Face 20220323_124917.jpg
    3 MB · Views: 44

Olds G's

Greasemonkey
Thread starter
Apr 6, 2020
119
43
CT
I've attached a couple of pics. Service manual states that the only field serviceable items are the backlight lamps. I did take the face off and will deoxit the board just the same. Using a true analog meter I checked the chassis ground. I did not have much luck looking for a signal that would indicate me pressing any selection keys (warm, cold, lo, auto, hi, def) so I figure it's looking for power to complete that signal. With that theory, I'll have to plug the ECC back in and access the ECC Programmer and back pin it at pin S to check temp change command from the ECC, pin U for mode select command from the ECC and pin M for power out (to the ECC power module). To go further I can also check pin N ground, ground G243 and learn a bit what I can do with pin W ECC diagnostic connector.

So, here is what does work when selected and the associated lamps:
Auto
Warmer (there is no lamp for this function)
Defrost

Here is what does not work when selected nor the associated lamps:
Cooler (there is no lamp for this function)
Off
Econ
Lo
Hi
Defog
Outside Temp
 

Attachments

  • Cadillac ECC Back Face 20220323_124917.jpg
    Cadillac ECC Back Face 20220323_124917.jpg
    3 MB · Views: 41
  • Cadillac ECC 20220323_112954 (1).jpg
    Cadillac ECC 20220323_112954 (1).jpg
    1.3 MB · Views: 46
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ELCAM

G-Body Guru
Jun 19, 2021
808
93
Red arrow - this board was wave soldered in a machine poorly, all the orange stuff is flux from hand soldering. It was reworked at the factory or repaired by hand. Clean that off with alcohol and a brush. Then look at them closely see if any look "cold".

Yellow arrow - some of those solder joints look "cold" I would reheat and reflow them all by hand.

Green arrow - those are pins that go in a connector I assume. some of them have a lot of solder on them where it does not belong, have they damaged the sockets they go into?



Cadillac ECC Back Face.jpg
 
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Olds G's

Greasemonkey
Thread starter
Apr 6, 2020
119
43
CT
Thanks 303'505rollin and Elcam,

I cleaned the board and the pic is attached here. Forgive some of the Q-Tip fuzz; it was removed since. Close inspection revealed no failed solders or cracks after cleaning with Deoxit but it took some time to get the board clean. I re-connected the ECC and ran the engine. All the functions of the ECC operate now. All the backlighting, LED for appropriate selections work. I am able to select warmer and cooler temps as advertised in the troubleshooting tree. The last item to t-shoot is that the compressor still does not engage when commanded. I jumped the compressor cycling switch and it did engage. Now that I can select 60 deg, the R-12 blows cold indeed. Selecting to 90 results in warm air in the heater ducts, back to 60 deg results in cold air out of the dash vents. Performing the same for defrost is good as well. The outside temp selector operates. The rear window defrost operates.

Next step is for me to get my Snap-On Solus Pro connected again and see what's what with the low pressure switch and the compressor cycling switch. So far it looks like I'll have time tomorrow.
 

Attachments

  • Cadillac ECC Back Face Cleaned 20220323_142307 (1).jpg
    Cadillac ECC Back Face Cleaned 20220323_142307 (1).jpg
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Olds G's

Greasemonkey
Thread starter
Apr 6, 2020
119
43
CT
Update for today:

I used the flow chart in the GM shop manual for the Brougham that calls for a test light to check the condition of the various circuits. What I did find was the Air Conditioning Cycling Switch was faulty. Earlier in this thread I mentioned that I had jumped to get the compressor on so I could add R-12. This was a clue but did not rule out the health or condition of the other components in the system such as the A/C Cut-Out Relay or the Low Pressure Switch.

Using the test light method I was able to confirm that the sole component at fault is the Air Conditioning Cycling Switch. I gave the switch a tap and the A/C clutch engaged. I ran the system through all the checks with no faults, twice. The switch does work now but I'll bet it won't when I actually need air conditioning lol. GM part number 3046588 had been discontinued since 2010 but a quick check showed a few GM dealers with one or more still on the parts shelf. The dealer I called gave me 25% off cost (not list) so after taxes I paid $21 for an NOS GM part plus the $15 to ship it to CT via UPS Ground. It's a small part so I asked that it go into a 12 x 12 x12 box and I'd eat the difference in shipping cost. Small boxes get lost in shipping. I should have it next week. Once I install the replacement part, I'll update this thread again.

If anyone out there in GBody Forum land has a 1988 Cadillac Brougham, I have all the GM books for this specific year including the Fisher body manual and I'm happy to help our members out.

The GBody Forum is fantastic and very proactive. I need to work on my proactivity and help others a bit more and I will.

Next project is to replace the A/C compressor on the 1984 Cutlass Supreme Brougham coupe. The original compressor turned into a bag of marbles but hoping I can tear it down and rebuild. The NOS R-12 compressor that I got from my local GM dealer was around $240.00 so I figured I'd best get that before I have to hunt one down in the event the original compressor is beyond economical repair. I have an R-12 machine to pull it down, evacuate and service it. I still have 17 pounds R-12 in my tank.
 
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Texas82GP

Just-a-worm
Apr 3, 2015
7,733
113
Spring, Texas
I've seen those clutch cycling switches hang up and then be fine. Back in the 90's, I put a 307 in an 84 Cutlass. The A/C was functional when I pulled the engine so I left the compressor connected and left the system charged. The car was apart for maybe 6-9 months before I got it back together. When I did, no A/C. I jumped the switch, cold A/C. Pressures looked good. I plugged the switch back in, fully functional. Never had trouble with it again. You probably can't go wrong with a NOS replacement though. Just check the box for where it was made. Post up some pictures of the Cadillac, if you don't mind. It sounds like a really clean old survivor. I like those.
 

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