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DeVille 1988
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Discussion Starter #1
Hi,

a couple of days before I have got a problem with my ODO. I solved this Problem by replacing the BCM behind the glove Box.
Now I've got a new problem. I hear relativ often my Cooling Fan Relay (right beside the glove box) very fast clicking and then the Cooling Fan Light on the ODO goes on.
I've already replaced the Fan Relay but the Problem is still present.
Can anybody tell me wich unit is responsible for activatig this Realy?

Regards
Julius
 

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1992 Sedan Deville, 1984 Lincoln Town Car
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759 Posts
did you mean the fan for cooling your interior (blower motor) or the big fans in front for cooling the engine? Was the relay in the Relay Center with 8 or nine relays, where there are also 8 fuses. If so one of the fuses #4 is for the Blower motor. Which relay did you replace?
The A/C has a relay but it's under the hood where the MAXI fuses are.

What exactly is the message displayed when the problem occurs?

the blower motor itself is controlled by a Power unit mounted under the hood and plugs into the motor. Near the glove compartment is the programmer controller with a group of vacuum hoses attached to it for air temperature control.
 

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DeVille 1988
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Discussion Starter #3
I mean the big Fan for Engine Chiller. Thats the Symbol I found for this Relay.
Near the Relay are 8 Fuses. The Relay I have replaced is under the Relay for defoging the rear window. And under the Relay I have replaced there are two Relays in paralell for Fuel Injection or Engine Control.
I hope now you know which Relay I mean.
 

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1992 Sedan Deville, 1984 Lincoln Town Car
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There are more relays under the hood, behind the battery. there is one for the radiator fan. Maybe that is stuck on or off. Does the fan turn on/off normally? the relays are interchangeable.
You could try interchanging the relay with one of the other ones to see if that solves the problem
 

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DeVille 1988
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Discussion Starter #5
The Relays are not the Problem, I have checked it and interchanged them, they runs well. I still don´t know what the function of the relay beside the glove box are. :confused:
Now I have located the Relay for the Chiller Fan. And this stupid thing is clicking in the same strange wise like this beside the glove box.
If I remove the glove box relay the Fan relay under the Hood shut off.
I thing this error causes my blown head gasket because the Chiller Fan doesn´t run well with this fast clicking relay. :want:
Anyway, If I switch the Relay beside the glove (which is signed with an Fan too) by hand so this is no reason for the Relay under the Hood to switch the Fan on!
So which ****ing control box is responsible for switching the Fan relay under the Hood and the "Fan" Relay beside the glove box?

It´s really important to know before I fix the Head Gasket! I don´t want to make it twice!
 

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1992 Sedan Deville, 1984 Lincoln Town Car
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Can you use the On-Board Diagnostic system to get any codes please?
Are you saying the engine overheated and blew Head Gaskets because the radiator fan did not operate? If so, maybe Thermostat is bad, and or Water pump.

but meanwhile
Fan is turned on by the PCM which gets data from COOLANT TEMPERATURE SENSOR wired directly to the PCM (Power Control Module)

You can read ohms.
CTS = 185 ohms @ 210F or 99C temp (low resistance)
7500 ohms @ 40F or 4C temp (high resistance)
Location: Top of engine near Distributor
 

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DeVille 1988
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Discussion Starter #7
The Onboard DIagnostic get the error Code E30 E52 and F41.
The E Codes concerning a bad idle in cause of the blown head gasket.
But I don't know what the F41 code means.

Anyway as next I will check the Coolant sensor, the wires are okay.
And I ordered a new PCM together with my engine :mad:

I hope the new PCM will fix the Fan problem otherwise the Fan gets a manual switch...
 

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1992 Sedan Deville, 1984 Lincoln Town Car
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E30 = ISC Out of range. E52=PCM Memory reset.

F41=Coolant Fan Problem (DUH!)
My opinion only, PCM seems to be working okay. It knew there was a problem and told you about it.(shrug) Recommend to not replace it until you are sure what is causing the problem. PCM replacement can mess up your Theft Deterrent VATS, and/ or PASS key system.

FYI, your model has also a cooling fan control module. It's located in the front of the car behind the grill on the passenger side.
here is a link from a fairly recent previous thread that might help you:

http://www.cadillacforums.com/forums/ht4100-4-1-4-5-4/166700-coolant-fan-problems.html

Here is another link. There are DIAG procedure for this problem for which a Service Bulletin was issued.The problem might be your FAN - not the PCM or Coolant sensor!!!!!

http://autorepair.about.com/library/faqs/bl193f.htm

Not to ask a stupid question but I am curious what makes you sure the HG is bad?
 

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DeVille 1988
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Discussion Starter #9
Thanks for the Info concerning PCM. Unfortunately I´ve already ordered it but I won´t replace it. Otherwise I have no Anti Theft System...
Anyway I´ve checked the coolance Temperature Sensor with cold engine he get´s 3,2kOhm not the Value as your detail. Could these the Problem? I don´t think so because the Fans should work proper only to early.

I can´t find the Fan Control Module I´ll search tomorrow when is more Light outside.

I guess I try the override with the onboard diagnostics... I´m tensly.


Concerning Head gasket: 5mls needs 0.5 gallons Coolance and a huge white smoke cloud, still questions???
 

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DeVille 1988
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Discussion Starter #10
I have made further tests:

If I unplug the coolance temp sensor the relays begins to fast clicking with turning on the Ignition. I gues the PCM know thats the sensor is missing and starts prevention with turning on the Fans.

I have made the Onboard diagnostic override. When the fan should go to high the Realys also begins with fast clicking.

I have removed the cap of one Relay (under the hood behind the batterie) so i can switch the Fan manual. Both Fans still works proper. But I can´t measure the current because I have not the necessary equipment. :helpless:

I have also searched for the control module. I can´t see anything behind the Grill on passengers side. You are sure that I have such an controller?
What does the controller switch? The Relay`s or the Fans?

So what should be my next step?
Do you have instructions for checking the Fan Control Module if I find it some day?
If the Fans needs to high current wouldn´t it blown the Fuses?
 

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1992 Sedan Deville, 1984 Lincoln Town Car
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Concerning Head gasket: 5mls needs 0.5 gallons Coolance and a huge white smoke cloud, still questions???
No, sir! :eek: so you will be busy,:stirpot: If you are planning to do the work yourself, You should obtain a Factory Service Manual. They are on Ebay-cheap. Maybe check the thermostat for damage could also be a problem why the engine overheated.

If I unplug the coolance temp sensor the relays begins to fast clicking with turning on the Ignition. I gues the PCM know thats the sensor is missing and starts prevention with turning on the Fans.
Anyway I´ve checked the coolance Temperature Sensor with cold engine he get´s 3,2kOhm not the Value as your detail. Could these the Problem?
Yes, based on your tests so far. at least part of the problem. When you unplugged it the PCM sees "open circuit". did you check the wires to be clean and making good connection? but check it when it's hot for the 185ohms to be sure. Since you are not driving the car because of the HG problem right? then you can remove the sensor and dip it in some boiling water from the stove then check it that way. when you got the 3.2 K Ohms what was the outside temp? if not 40F near freezing (32F= frozen water) then I am not sure what the reading would be. Put it in the freezer for a few minutes and check again? The ohms should go way up (7.5K). but boiling should go way down to 185. If not, then the sensor is bad or intermittent.


About the controller, forget it if you can't find it. I was only quoting from an entry in the link I gave you, the one posted above about the 89 Deville. "Codewize" He must have meant the "blower moter". it has a control unit.
My car doesn't have one for Cooling fans, but it's 4 years later. The fans would have wires going to it if it does exist on the 88 deville. I know my circuits work the same as yours even if wiring is slightly different locations (GM engineering, always similar for these years).

Circuit works like this: PCM has 2 fan outputs. One is low speed the other is high speed. Really there are 2 sensors to feed the data to the PCM. The one I told you already CTS. The other is the Refrigerant High Side Temperature Sensor from the A/C mounted on the A/C line (location on my car is RH engine compartment behind headlights.) Refrigerant sensor data helps make decisions for the radiator fans. RHSTS goes to the BCM first then BCM sends data for PCM to control both fans. if needed I will post the wire colors and position for you to check for 5 volts PCM and BCM (if you have not yet torn all your hair out by then)
 

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DeVille 1988
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Discussion Starter #12
Head Gasket, well shit happens!
I hope end next week my engine will be replaced. To fix the head gasket is a sensless job. No way to get cylinder head bolts out without damaging the thread in the bottom fo the crankshaft housing.... :thepan:

So I will test the coolant sensor again. I don't think its his fault.
Do you have some values for the A/C Temperature sensor, because I don't have any refrigent in the system... thats another construction side....

No kidding, I guess the PCM is fault. What do you thinking about an bad transistor which breaks down if he try to switch on the relay. Then the circurit is disconnected, he gets "healthy" try again to switch and breaks down again and so on. This could be the explanation for this fast clicking. Couldn't it?

Do you really think I get a pproblem by replacing the PCM? Don't forget I 've no Anti Thaft system in my car, no RFID Key or e.g.

The wire colour and positions would be awesome...:thumbsup:

I've already shoot a manual on ebay. I guess I'll get it today, I hope I'll get it today!!!
 

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DeVille 1988
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Discussion Starter #13
I got the solution! :alchi:

My first post was about non Function on my Odo. So I replaced the BCM.
The BCM has an EPROM. The Eprom from the replaced BCM has another Program than my original. So I changed the EPROM´s and the Relays are switching proper!!! :thumbsup:
But that´s not enough. I am distrustful so I checked the complete Fan Harness. The Relay for High Speed was blown up too.
By the way, on the Strut dome are three relays. All of them are reponsible for the Fan (low, mid and High Speed) and all of them are controlled of the BCM!
And one of the Fan Resitors are blown too. So Low and Mid Speed don´t work.
Awesome, or not?!
Whats not blowing off in this Car????
But the main issue High Speed Fan are working now. The other Speed will be fixed when I get a Junk Yard...

By the way, the service Manual from Cadillac is very helpfull!!!! :thumbsup:

Thanks for your help.

We´ll see us. Soon....probably
 

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1992 Sedan Deville, 1984 Lincoln Town Car
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VERY TERRIFIC !!!!!!!!!!! Once you said "the manual might arrive today!" I knew soon you would have fun and get the solutions to everything.

Yes I was surprised the BCM seemed to work without changing the EPROM, but why open my mouth with too much information if it was working? Sorry, I should have mentioned this part about the EPROM you need to change it out. Similar procedure with the PCM, if you use your new one be sure to use the old one brain MEM-CAL UNIT. My book is chapter 6E-C1-Powertrain Control Module. be careful!

Now I learned something new too. Also, others with this problem can read the thread and learn. Thanks!!:highfive:
 

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1992 Sedan Deville, 1984 Lincoln Town Car
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OOPS! Important one more item for you. Your engine has cast iron cylinder heads so you do not need new cylinder head bolts just to put in NEW Head Gaskets!! :thepan: Just clean them with engine oil. make sure they don't strip going in.

That problem is only on the later model Northstar engines that have ALUMINUM cylinder heads, much weaker metal that the old bolts can't be used. Most mechanics choose to replace the whole Northstar engine rather than do this procedure.
 

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'87 Sedan Deville
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Note: 1987/88 Deville Location of Radiator Cooling Fan Control Module

Howdy . . .

Just passing through and thought I would add some info related to the location of the radiator cooling fan control module. The following remark was left upthread and if any one scrolls through the thread my comment may help clarify the location on the 87/88 Deville.

About the controller, forget it if you can't find it. I was only quoting from an entry in the link I gave you, the one posted above about the 89 Deville.
I have an '87 Deville I've owned since new. The cooling fan control module is located on the driver's side, behind the head light back between the front cross wall and the back of the headlight box. You can see it by bending over the battery and looking through the two holes in the cross wall. It's a pain in the butt to get to to work on if need be, but what isn't?

Hope this helps.


~.The Duck.~

 
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