Hi, My 1989 Deville heater blower motor started being intermittent and then quit entirely. I have already replaced with new parts the ECC module in heater box, the blower motor itself, and the heater control module that used to display temp (temp display area now displays only either "c" or "d" as does the fuel gauge). I know tha car is low on freon but it is a winter car, so not surprised that once in awhile I also get intermittent "service air conditioning" and "service engine soon." Tried disconnecting AC sensors, but made no difference at all. Car runs great and never falters but Minnesota is a tough place to drive without a heater. As I have been replacing these components I have disconnected battery and hooked up negative last so as not to confuse computer. I am beginning to think main computer must be haywire because replacing these other components usually did nothing, or if behaviour changed it was only temporary. For awhile, my cooling fans got in on the act and both ran nonstop and I had to disconnect battery morning and night. Cooling fans have not been doing anything funny altely and come on and off as they should, though I did nothing to them except unplug and replug their relays. Later on, the heater started running 100% of the time when the car was running though I had not control over heater and fuel gauge showed nothing except "c" or "d". That lasted about a week and then heater conked out entirely again. Blower still turns when power put to it, but hardly ever otherwise. Dynamite? Mike H MN

 

c (clock) d (data) relate to bcm. It maybe the cause, codes?

 

has its own onboard diagnostics. That explained why I could not locate plug for my code reader. Body Control Module, according to my "manual" appears to be incorporated into heater control box/display module and should display codes with the pressing of certain button combinations. Manual says if you can't read codes must first replace the component that prevents getting codes. (Like what, the entire car?) It does not say what that component might be or list the possible components, but it appears to me that there are at least three possible components:
1 - the electronic climate control module (some people call this the body control module too though, so that makes it more confusing - anyway it is the one in top of heater box on engine side of firewall and manual calls it ECC module ).
2 - What I think of as the body control module which appears to me to be built into the heater control panel and should diisplay codes but won't even though replaced already.
3 - the main ECM. Since I have already replaced the ECC climate control module (twice) and the heater control and panel (BCM?) once, as well as installing a new blower motor.
Only part left I thought would be main computer ECM? Only once did I ever see what appeared to be a code in the fuel data center that was a
".. 7.0" and I only saw that one time. Otherwise displays are random and appear to change ocassionally from "c" to "d", to normal displays of fuel & temp, thenback to nothing or "---", then back to "c" and "d" when triggered by sensors detecting low freon(?) in A/C circuitry. Service engine soon light on most of the time(80-90%, service vehicle soon light on 10-15% of time and service air cond. light on 1-2% of time. It is like driving a view of Vegas at night. I cannot elicit any codes as my manual says I can. A post for another model Cadillac says there is also some kind of electonically controlled heater door actuator box that fails frequently. I hear something operating in there behind the dash occasionally and surmise it is that door moving because car infrequently alternates between ambient warm air draft from heater and ambient cold air draft from heater when on freeway moving. Went on 160 mile round trip last night (hockey game )and it was ambient cold draft 90% of time but ambient warm draft 10% of time. Heater blower never came on once during trip but did for 5 seconds yesterday afternoon when reprogramming radio buttons again due to battery being disconnected. Coolant level is not low. As you intimated, I need codes, but cannot get any so have to replace whatever component is stopping me and neither the Chilton's book or I know what component is responsible for that. So, I will try replacing the main computer since bizarre intermittent problems in a 92 Eclipse and in another car I had did stop after replacing main computer. Some say that ECM either works or not, but I have seen more than one car with symptoms that went way after that replaced. Anyway, can't see many more parts I could replace and I will just hotwire damn heater motor with a horn relay and toggle switch and also block heater door and water control valve to heater open if ECM doesn't solve problem. For lack of gas gauge I am getting used to trip meter reset at every fillup. Any more components I am overlooking that could cause all this? Thanks, Mike

 

BCM sends information to Fuel Data Center (FDC) and Electric Climate Control Panel (ECC) When information is not sent or can't be interpreted c or d will display on panels.

Electric Climate Control

ECC Control Head - panel on dash
ECC PROGRAMMER or Programmer - control air doors and contains motor that actuates air mix door (hot/cold) - mounts on HVAC case under dash - has vacuum plug attached to it.
ECC Power Module - Controls blower and can effect compressor operation. Mounts on evaporator case in engine compartment.
BCM - Body Control Module - Controls many body functions including Climate Control along with receives inputs from various sensors along with ECM. BCM is behind glove box above HVAC case on bracket.

ECM is unlikely to solve your concern, you need to invest if FSM.

 

Is this the ECC Power Module?
http://www.autozone.com/autozone/cat...questid=558715

And is this the BCM?
http://shop.advanceautoparts.com/web...S_569594527___


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I have been having similar problems and cannot locate an FSM to verify.

I want to replace these parts and get the Caddy running correctly again. It's already getting HOT here in South Georgia.

 

Previous poster that said it was BCM was probably right. I had already replaced ECC module several times and it kept conking out (heater motor replaced too as I hear if motor is poor it knocks out ECC module). Nevertheless still no blower or gauges or ability to pull codes as previously mentioned. I finally went to junkyard and pulled a BCM, fuel gauge, heater control, a replacement glove box door (cover loose) and a few underhood relays while I was at it. Guy charged me 40 bucks which I thought was pretty cheap. Installed the fuel & temp displays and BCM and I have gauges now. However, heater still did not work and found that the connector at heater deteriorated inside (resistance generated presumably). After trying the collection of ECC modules I already had, none worked (4 did nothing, one ran fan all the time whether car turned on or not) so back to yard and got two more ECC modules and a good heater connector for another $10. Put them in and everything is working (though I did have to put master cylinder in two weeks ago and front brake pads in yesterday so I am getting pretty familiar with that car. But it is going into storage tomorrow til fall and hopefully nothing else weird happens while it sits. Mike

 

i've had the same problem my fuel gauge and temp gauge would always display c i've replaced the BCM and ECM after replacing both my fuel gauge and temp gauge both worked fine for a few minutes then my fuel gauge displayed d and my temp gauge displayed 32c my A/C and my heater never worked since i've bought the car next i was planing to replace both fuel and temp display, were can i locate the ECC module so that can be replaced? Dominic thanks