: 1998 Deville, Both Cooling Fans fail to turn on when commanded with TECH II



brianroark
03-08-11, 09:40 AM
I have a 98 deville and both of my cooling fans fail to come on. I have a Tech 2 and have commanded the low speed, high speed and all relay. None of these functions command power to the fans. I only checked for voltage at the high speed fan since this is the easiest to pull off and I am not getting 12 volts with any of these three functions enabed on the tech 2.


I checked the 50 amp maxi fuse for the cooling fan and it is good.

Can someone please help me. I was going to buy a new relay and plug it into each of the three relay's one at a time and hope I can get one or all of the fans to turn on and go this route. Can someone experienced give me some input.

Thanks

mhamilton
03-08-11, 10:46 AM
The schematic is in post #11 here: http://www.cadillacforums.com/forums/cadillac-seville-cadillac-eldorado-forum/172816-not-overheating-driving-but-overheading-idling.html

http://i29.photobucket.com/albums/c296/Krashed989/Fans.gif

Check your A/C Compressor fuse. This supplies solenoid power to the relays, the PCM provides a ground to enable the relays to close. Check for 12v at the Maxi-Fuse supplied terminals of the relays (red wires)... then check for 12v at the solenoid supply (orange wires). If not present, then you have an open wire. Not as odd as you might think--I found the fan harness melting against my exhaust manifold when I got my car. Luckily no wires were burned through yet.

See what you get with that. If you need more help with the schematic, I'm happy to walk you through it.

brianroark
03-08-11, 11:18 AM
I replaced two of the three relays, and alternated between two of the old relays on the far left bank. still no fans. the a/c compressor is leaking and there is no refrigerant, The car hasnt overheated yet but It is becoming a pain driving with the heat on full blast. What are some common reasons? The three relays going back to the main harness are not melted at all.

brianroark
03-08-11, 11:31 AM
I am not using air conditioning so I think I can bypass anything to do with that system and I'm guessing i should be focusing on relay one and the wires prior to that right?

brianroark
03-08-11, 11:35 AM
another thing, how are these fans grounded and where is the ground contact point or bolt? the relays are laying free right now on the radiator core support, this shouldn't make a difference should it


checking ac compressor fuse, im taking it the pcm send the ground signal for the relays and the ground for the fans.

brianroark
03-08-11, 12:13 PM
The a/c compressor 10a fuse is good. i'm at a loss, the connector on the low speed fan is a little loose, would this have anything to do with the high speed fan working independently of the other fan.?

brianroark
03-08-11, 12:33 PM
looks like a fun afternoon of various tests probing the relay harness's, power distribution and fan harness's with the multimeter. NOTT

brianroark
03-08-11, 12:35 PM
what kind of signal should I be getting from the pcm with all relays commanded on the lt green and blue wires. continuity to ground right?

brianroark
03-08-11, 12:38 PM
ignore me, I have the wiring schematics and I'm dumb enough to ask stupid questions. or any questions and not follow the schematics, when I know how to read them and figure this out myself.

Thank you that's all folks.

brianroark
03-08-11, 12:42 PM
one questions i do have, the left hand fan is the passengers side when standing in front of the car, and the right hand fan is the drivers side? or is everything always referenced as if you are sitting in the drivers seat?

mhamilton
03-08-11, 12:49 PM
still no fans. the a/c compressor is leaking and there is no refrigerant, The car hasnt overheated yet but It is becoming a pain driving with the heat on full blast. What are some common reasons? The three relays going back to the main harness are not melted at all.

Refrigerant won't affect whether or not the fans work. With the ac not functioning the hvac will not command the fans on, but they should still work if commanded by an engine or transmission temperature condition.


I am not using air conditioning so I think I can bypass anything to do with that system and I'm guessing i should be focusing on relay one and the wires prior to that right?

No, don't mess with the ac sensors, they have no bearing on the fan's functioning.


another thing, how are these fans grounded and where is the ground contact point or bolt? the relays are laying free right now on the radiator core support, this shouldn't make a difference should it

checking ac compressor fuse, im taking it the pcm send the ground signal for the relays and the ground for the fans.

The fan motors are grounded somewhere in the harness. In the schematic, the large gauge black wires go to the ground distribution. The RH fan motor is direct to ground, and the LH fan is grounded through Relay 2. I do not know where that ground point is. But, you can easily test it with an ohmmeter. Unplug the RH fan connector and measure resistance from the black wire to chassis ground. If it's 0 ohms, your ground is fine.


The a/c compressor 10a fuse is good. i'm at a loss, the connector on the low speed fan is a little loose, would this have anything to do with the high speed fan working independently of the other fan.?

So you're saying one fan works in high speed mode?

Before swapping relays and chasing ghosts, you need to do some simple diagnostics. These are not hi and low speed fans--the fans are the same but connected in series for low speed (each motor sees ~6v), and then connected in parallel for high speed (i.e. normal 12v to each fan motor). If neither fan works in high or low, it has to be a power supply issue (either 12v or ground). If the RH fan runs in high but the LH never runs, then the problem is with the LH fan itself. Either the connector is loose, or the motor is bad. I would bet the connector if you have just the one motor not running.

For further diagnosis, what I would do is get a test light. Pull relay 1, 2, and 3. Check for 12v at pins (85, 30) (85, 87A) and (85, 30) respectively. Check for ground at the pins 87 of both relays 2 and 3. Put back relay 1. Command low speed fans, relay should click. Remove 1 and install 2. Command high speed, relay 2 should click. Remove 2 and install 3. Command high and 3 should click.

brianroark
03-08-11, 01:22 PM
yeah thats what im planning on doing figuring where I need to run a new ground or fused hot wire to relays if I cant trace where the problem lays in the circuit.


left or right is considered sitting in the drivers seat right?

brianroark
03-08-11, 01:27 PM
I've done this kind of work before, just guess I'm being lazy and under confident. I can read and understand everything on the schematics which shows the structure of the system. I think the biggest thing is when I look at a problem before I investigate or look at the diagrams is I get overwhelmed instead of jumping into it with confidence. What I meant by bypassing the A/C system is not pointing any fingers at it and ruling it out, because the fans will not work if it signals the ecm to activates them. I am more concerned that in whichever mode the ecm commands the fans whether it is a, a/c load duty or regular temp 222 or 238 trigger, the fans are not running in any of the variables. Which is why i agree when you told me you think it is a power or ground supply issue. I could have used better wording and slowed down I guess. The only part of the A/C system I have to worry about is the constant 10amp feed through the orange wire to relay terminals 85 which supply the the positive polarity for the relay switching function. The Red constant at 30 on relay 1 & 3 for fan postivie power. The ecm supplies a ground signal to 123 for high, low or combined with green and blue only while energized (commanded) under normal trigger conditions or manually for diagnostics. the fans main constant ground supply should be checked at the black harness for the lh fan and continuation at the drk blue wire on relay 2 for the rh motor. Sound about right?


I really appreciate your time but I think I was just being lazy and had a lack of confidence to not just jump into it with the diagram and attack this problem by myself.

Submariner409
03-08-11, 01:47 PM
Post #4: With no A/C commanded the fans will NOT come on until coolant reaches 224 degrees, when both go to SLOW, coolant goes down to 213 and fans turn OFF. If you're in really hot ambient conditions in traffic with A/C OFF, then heat may go to 236 in which case fans go to FAST, then SLOW at 224, then OFF at 213.

With a properly operating A/C system commanded ON, fans run in slow all the time.

brianroark
03-08-11, 02:04 PM
RH motor has switched positive and LH motor has switched Ground.

mhamilton
03-08-11, 02:11 PM
Which is why i agree when you told me you think it is a power or ground supply issue. I could have used better wording and slowed down I guess. The only part of the A/C system I have to worry about is the constant 10amp feed through the orange wire to relay terminals 85 which supply the the positive polarity for the relay switching function. The Red constant at 30 on relay 1 & 3 for fan postivie power. The ecm supplies a ground signal to 123 for high, low or combined with green and blue only while energized (commanded) under normal trigger conditions or manually for diagnostics. the fans main constant ground supply should be checked at the black harness for the lh fan and continuation at the drk blue wire on relay 2 for the rh motor. Sound about right?

Left and Right is from driver's seat... so left is the driver's side, right is passenger.

I doubt it's a broken ground or hot wire, since you mentioned one of the fan motor connectors was loose it's likely to be that. If either fan motor is disconnected or open, you will get no slow speed operation. But the other fan will still work in high speed mode.

But yes, if neither runs in any mode, then I'd look to power and ground.


the fans main constant ground supply should be checked at the black harness for the lh fan and continuation at the drk blue wire on relay 2 for the rh motor. Sound about right?

Just check the wire color again (I saw the same thing, look to the right and you'll see "3 Black")--dark blue is 0.35 gauge ground trigger for relays 2 and 3... all the grounds are black heavy gauge.


With a properly operating A/C system commanded ON, fans run in slow all the time.

Also add to the criteria that if the a/c high side pressure goes over 200 psi the fans will switch to high speed mode as well (regardless of engine temp).

Though obviously not an issue here, since the OP's ac system is disabled.

Submariner409
03-08-11, 03:30 PM
RH motor has switched positive and LH motor has switched Ground.

Take a look at the wiring diagram again - the fans are relay set to series operation for SLOW speed - voltage drop. HIGH is parallel operation - full voltage to each motor.

(Same principle as the DRL system)

brianroark
03-08-11, 05:15 PM
Sub: I ment at the motor themselves, it looks like one motor goes directly to ground and has a positive switch through the relay setup and the other is hot but has a switched ground though the relay.

mhamilton
03-08-11, 05:59 PM
Sub: I ment at the motor themselves, it looks like one motor goes directly to ground and has a positive switch through the relay setup and the other is hot but has a switched ground though the relay.

That's partly true...

The LH fan has a switched positive and ground. The RH fan has only a switched positive. The circuit changes between putting the fan motors in series to parallel.

In slow mode, LH has 12v at top, bottom is connected to top of the RH fan, which then has a ground. So you have [+12v]----[RH motor]----[LH motor---[Ground] and both spin at half speed

In fast mode, both have 12v at top and ground at bottom.
[+12v]----[RH motor]----[Ground]
[+12v]----[LH motor]----[Ground]
both spin at full speed


Were you able to test those voltage points mentioned earlier?

AJxtcman
03-13-11, 07:15 PM
Brian I will take that 2nd Tech II from you

Hey you can always give me a call. Your brother has my number if you have lost it.

brianroark
04-10-11, 02:05 PM
AJ thanks, Im keeping it though, heh,

Problem was with the A/C fuse, fuse was good, originally tested it with the multimeter and the open contacts on the top of the fuse but most of all the fuses in the block had corroded blades on them, I ended up sanding down all the fuse blades and making good contact for the 30 some odd fuses.