1980s 1980 CADILLAC ELDORADO DEFI, IS THERE A SEPERATE ALDL CONNECTOR??

[BMason4575]

Good Morning all, I have a very nice 1980 DEFI that has a hard CEL light. I am unable to use the ECC panel to obtain codes. it only Shows .. when Diagnostics are entered. the AC section works fine. The MPG is also dead. I have checked fuses and looked for disconnected connectors. I do not want to start replacing parts and guessing.I was told there is a diagnostic connector under the dash on drivers side by the courtesy lamp. I can not find it. nor can I find it in the GM wiring manual. Another strange issue is that the ac blower runs all the time when vehicle is key on and or running. I am thinking grounded circuit but I am for obvious reasons (my Back and Neck) trying to do this the logical way.(ask people smarter than me.) One other thing the timing connector to check timing says p/b wire disconnect and ground (yup can not find it.)
Thanks Bruce 3863167332

[TJ Hopland]

1980 had a separate electrical manual which I have handy, its a 'sideways' book, blue cover white text.  I also have the full 1980 service manual which I can't lay my hands on at this moment.  Quick look though the electric manual which doesn't go deep into the DEFI diagnostics I didn't see any mention of a/the diagnostic connector but this book also doesn't talk about that sort of diagnostics so there may not be any reason to mention it here.

Does it run just has a check engine light?  What's the history of this car like how long have you known it and how long has it had this issue?   One thing that can cause these com issues is if the computer and or the 'chip' has been changed. 

I'm not positive this is how it worked in 80 being the first year but in slightly later years the chip had the specific details about that specific car and its options and how to communicate with those options which would be things like the climate control and mpg readout.  Yes its true that in 80 none of that was an option but maybe the computer and or chip that got swapped in wasn't from an 80 or even a Cadillac.  Engine may run because all the EFI engines in that early era had basically the same stuff its the rest that may be different. Maybe it was from an 81 and in 81 all the communication channels were shifted over one due to the 8-6-4 feature?  I don't know that just using it as a possible reason that 80 and 81 could have been very similar but not the same.

80 was just Eldo/gas optioned Seville that got the DEFI.  81 many of the carb cars got a computer and there was the crossfire system in the Vettes so there were getting to be a lot more of these same basic computers out there.  By 82 there were a ton of cars that got em, I think it was only the trucks that didn't have full computers so 82 was really the year the GM computers kinda settled into a standard so these 80 and 81 were kinda their own things that were unique.

I will try and keep an eye out for my full 80 manual,  I know I own one just don't remember the last time I looked at it.  I don't recall loaning to anyone so I should have it somewhere.  I'm pretty sure the 80 full manual has the troubleshooting for the DEFI broke down by codes so that should talk more about things like the connector and data lines.  At least I hope that is in that manual, fairly sure 81 has that so if the 80 doesn't I can look at the 81 and hope its the same?


On the blower front stuck on is a possible failure mode for the blower control module,  like the DEFI this was the first year for a digital electronic climate control too and likely 1 or 2 year only parts till the reduced the number of bugs and kinda settled into a groove.  Another likely cause is that the module failed at some point in the past and someone just bypassed the auto controls and either wired it to always be on or installed a manual switch somewhere you have not found yet.

Blower gets a constant (not even keyed) power feed on an ORANGE wire.  Ground is what is modulated by the control module on a TAN wire.  The ground that the module eventually connects to the blower I believe is a black wire that just comes out of the module.  Diagram says its black, what I don't remember for sure is if its some sort of connector or if its just a wire coming out of the plastic.

Blower module connections:
TAN-modulated ground to the blower motor
BLUE-power out to AC clutch
BLACK(fat)-chassis ground used for the blower motor
GRY/WHT-looks to be some ambient temp switches related to the compressor control signal
BLU/WHT-looks like its some sort of control voltage between the brains and modules
BLACK(small)-looks to be the ground for the module power and likely data signals
ORN/BLK-is the blower control signal
BROWN- is the regular 12v unswitched power for all the brains and modules from the AC fuse.

Let me know if any of that helps or leads to more questions.           

[TJ Hopland]

I just walked by my older OTC scan tool and fired it up to see what it had for 80 and oddly Cadillac isn't an option.  Chev, Olds, Buick, Pontiac, GMC, and GM of Canada.  So its possible that maybe 80 doesn't have one?

I looked at 81 Cadillac is listed and for the DEFI it shows a breakout cable with individual wires that must get stuffed into something somewhere that must not be what became the standard Gm connector.  if I switch to the V6 option its a '5 pin' adapter so still not the standard one.   

[smokuspollutus]

No ALDL in 1980. Some other 1980 GM cars have a loose connector by the ECM harness that you can ground and make the CEL flash the codes. No idea if the Cadillac has that. However if you aren't getting codes from the climate display, 99% of the time there is an ECM problem and even if you could ground the connector it wouldn't be able to tell you anything. This is furthered by the lack of a fuel data display and constant CEL.

I hate to be one to blame computers and change parts but I have fought these issues on a few '80 models and the ECM/PROMS seem to have a pretty high failure rate. Sometimes it could be cured by a new computer.

The blower running all the time is normal on a 1980. It should run whenever the key is on.

[TJ Hopland]

Guess we should ask if the blower is running on low or high,  I assumed high since at least for Cadillac they had been running on low for years. 

[BMason4575]

Good Tuesday morning , I hope everyone had a nice memorial day. I have a update and a question. The update was I got the diagnostic panel working  and was able to extract service codes. someone had replaced the IAC motor and flipped the connector so the idle tracking switch was not working. repaired with a new IAC and connector, disconnected battery adjusted tps and idle all is now well. I almost forgot, I also cleaned the grounds and installed AC Delco plugs .060 gap. someone had rapid fires in it at .040 gap. Made a world of difference. My question is, Is there a way to disable the flow through ventilation system ? The client does not like it running when ac is off. I have the 1980 GM manual that you spoke about and read the description and operation and it seems that it is built into the system . Can it be overridden without reinventing the wheel?? Even disconnection of the heater turn on switch makes no difference. Any thoughts would be greatly appreciated. thank you in advance.
Bruce

[TJ Hopland]

Very strange thing to notice and complain about.  I don't think its like on modern cars where with the right tools you could re program it.  You would need to start hacking wires and add some sort of switch.

The power to the blower motor itself is constant, not even keyed so its not just 'baked' into the module to always run it must be getting a signal to run on low.  I would assume if you interupt that signal blower won't run.  A question would be can you just splice into that orange/black with a switch and call it good?  Or is there some possibility that not having a connection could pick up random voltage and noise and damage either the controls or module?  This was all 1 or 2 year stuff so probably very difficult to get replacements. 

What if the switch got turned on when the command was already being sent for max?  Would that damage anything?  Normally there is a ramp up.  Again this was the first year of electronic controls so they likely didn't know for sure what they were doing.  Did they over build and over protect everything just to make sure or did they under design things and beef it up a bit later?

To me seems like a lot of risk and hacking to get rid of something every Cadillac did since at least the 70's,  maybe earlier?

[BMason4575]

Those were my thoughts exactly. I was even thinking of wiring in a shut off switch after the controls to the tan power wire. You know if I did this something else would burn up and there wouldn't be a replacement part available and if it was it would be $$$$$$$$$$.
Thanks Bruce

[smokuspollutus]

It is a mildly infuriating feature as the compressor is not engaged all the time like it was in the earlier years. So if you turn off the AC you continuously get sprayed with damp evaporator air.

What's odd is neither the '79 nor '81+ did this. Not sure why they felt the need to do it.

The only way I could think to disable it would be to find a wire (if one exists) that is energized all the time when a system mode other than "OFF" is selected, tap it, and use it as a trigger for a heavy duty relay that breaks power to the blower motor. You may have to make provisions for a flyback diode on the trigger wire to prevent damage to the control system as the relay disengages. A look at the '80 wiring diagram would give you an idea if this is possible, or whether there is an easier way to do it.

As mentioned seems like a lot of risk to subject one year only electronics to for little gain. I would tell the client to find a temperature they like, run it on AUTO and leave it that way-at least that's the way it was supposed to be used.

Was computer diagnostic operation restored when the ISC connector was disconnected/correctly re seated?