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I was thinking cleaning the battery connection was going to be the right next step based your other explanations here, Bob and Stan. It makes sense as the the cooling fans are getting direct power from the battery.
Stan, you mention quality fuses - are they any particular brands you recommend? I suspect I have used whatever I had available, and knowing how sensitive our electrical systems are, quality fuses make make a difference. It may be worth it for me to do a total fuse refresh it you think it could help.
As for Deoxit I have D5 and 100 on hand, and I use 100 for these situations. As for relays, I got a bunch from Roger a while back, so I should be good there.
I still keep my smashed relay 53 from Frenzy a few years back in my glove compartment as a fond memento.
Replace all the ATC fuses with either Bussman or Littelfuse fuses - good insurance against other issues. Lots of cheap and crappy Chinese fuses out there. Even top quality fuses are not really expensive so don't risk it.
And again, the subject line of this thread is CORRECT! Stan, you never cease to solve my problems. While nothing was visually that dirty, I did try to be meticulous and cleaned up some things, like dried tape boots around wire connectors. i did replace the X-bus a few years back but I had extra 53s, so swapped it. I also changed Fuse 4 since I hear that it powered the X bus, and i honestly did not like the look of the fuse when I pulled it. I did notice that he passenger side fan plug is cracked and also know that the plug is hard to find. In the end, both fans are running when needed at the speed as desired.
And Alan, thank you for the tip on the fuses. Fuses just not seem like a smart thing to skimp on with these cars.
instead of starting a new thread, i will add this here.
i was having an issue with my cooling fans where only one would run(pax side). Started trouble shooting it today.
all fuses are good....both fans run when 12 v is applied directly to them.
tested the connectors and and found the driver side connector bad. Over time and probably numerous installations and removals the connector had been push far enough back in the plastic hosing where it was no longer making contact.
i had to cut open the boot and pull the connector through to get it reseated it.
Pin 5 - red/yellow (+) to passenger fan (from fan control unit)
Pin 8 - red/blue (+) to driver fan (from fan control unit)
Pin 1 - red from fuse 29
Pin 4 - red/white from fuse 28
This is a temporary fix.
Resurrecting this old thread. '93 GTS driver side fan is not working. Deoxit D100 the final stage module connector (showed some green corrosion), ground on the side fender to left of final stage module and the one under the headlight bar. Voltage at the 29 & 30 fuses is battery voltage. Verified fan is good by hot wiring. No voltage at the connector to this fan. I switched out the "fan final stages" module with another know good one from one of the other cars. No change. Wiring not damaged to the fans. Passenger side fan seems to run at full speed 80% of the time. I followed Dr bob's list of thing to check. No success thus far. Any other suggestions? What are the pin outs for "fan final stages" module on its wiring harness? Thanks guys............
Clarification: Test for voltage at the fuses in the panel. These are 29 and 30 for late model S4 & GTS cars. The fuses have small opening in the front face that lets you stick a meter probe in and test voltage
1) For fuses 29/30 with the fuse installed - test at the top opening on the fuse . Should be battery voltage, referenced to chassis ground - this tells you the dedicated feeders from the battery to the fuses are good
2) For fuses 29/30 with the fuse installed - test at the bottom opening on the fuse. Should be battery voltage, referenced to chassis ground - this tells you the fuse & top fuse holder connections are good
After following Alan’s test protocol
I would suggest the fuses at the fans be replaced and the wires at the battery be removed and cleaned your problem is usually one of these issues
Note how much friction the fuses require to pull out and install it’s possible your receiver pins in the panel have opened enough to prevent solid contact put deoxit into the CE panel fuse slots if the friction for the fuse is low then you can try to add solder to the Fuse blade
OR replace the fuse holders
I will check again the battery connection, voltage at both sides of the fuses (btw fuses were tight enough that I had to use a fuse puller instead of my fingers) and checking the connector on the fan to make sure they haven’t pushed through. “X” relay replaced last night. Will report back.
What work have you done on the car lately, at least since the fans last ran correctly?
You've done the basic stuff like clean and tightene all the connections at the battery positive post. Process continues with:
-- Test for voltage at the fuses in the panel. Thes are 28 and 29 for our cars. The fuses have small opening in the back that let you stick a meter probe in and test voltage at the top of the blade with the fuse installed. Should be battery voltage, referenced to chassis ground on bothj pins of both fuses.
-- Connect the two wires hat are normally on the intake temp switch, top of the intake manifold. This switch normally causes the fans to run on low speed with the key off and hood closed. So key off and either the hood closed or the switch taled down. Fans should run on low speed. Repeat the votage check at the fuses. Should still be full battery voltage referenced to chassis ground. Low or no voltage on any of those fuse points means there's a fault between the fuseholder and those smaller wires at the positive battery terminal.
-- VERIFY that the round plug on the "fan final stages" module is plugged in securely. That little metal retainer arm swings out of the way, plug can be pulled and reseated a couple times to wipe the connecting pins.
-- VERIFY that the wiring on the fan console is routed correctly, and that there is no damage to the wiring. The harness sections clip into the frame with little metal Z clips. I supplement those in a few critical places with small cable ties. Wiring needs to stay completely clear of the fan blades, the drive belts, and the lower radiator hose. where it's tied to the saddle on the fan console.
-- Pull and reinstall the harness connectors to the fan motors themselves.
Besides those steps, there are some electrical faults that might affect the operation of the fans.
-- The hood switch is part of the fan control scheme. WSM says that the hood switch will cause fans to stop when the hood is open. In my experience (my car only...) this protection is only afforded during the intake and auto trans overheat modes.
-- The radiator temp sender (described as a switch in WSM wiring diagrams) needs to be plugged in for fans to work. Front bottom of the plastic tank on driver's side of radiator on US LHD cars.
-- The fan "final stages" module seems to be the more fragile of the two electronic modules. Failure typically results in one of the fans not running correctly. It's possible that both independent channels in that module have failed. so don't rule out that possibility. Best/only real diagnosis is to pull your module and plug it into another S4+ car, see if it runs the fans the same in that car.
-- The controller module next to the passenger's seat lives a perfect life. Covered, shielded, on a climate-controlled environmnet, only sees low-level signals from a dozen different places. I've heard of only one or two failures of this module. But it could happen.
-- Controller and signal power come through different circuits than the motor power mentioned above. Fuse 3 protects part of the controller, routed through the X-bus relay. The controller also gets full-time power from the 30 bus, with no fuse protection at all. So fuse 3 and the X-bus relay (in position 4 on the CE panel) would be good places t look. You can do the same in-service power test through fuse 3 that you did for 28 and 29 above. However, the X-bus is only energised when the engine is running. (Key in run position 3, starter not engaged). So check that fuse with key on at least. As others have suggested, that X-bus relay powers the fog lights and other things like HVAC blower, so easy to check the relay by checking for fog-light operation. It's a standard 53B relay so replacement as a PM task isn't a bad idea.
-- HVAC fans, controller module and final-stages module all ground at ground point MP-II. It's an easy one, on the right side front just forward of the AC condenser and inconveniently under the headlight crossbar. Weather-exposed there, it's a good candidate for regular cleaning and resealing. Do the one (MP-III) on the other side by the ignition final stages modules, and the one (MP-I) on the fender wall just forward of the jump post WYAIT.
Well, Dr Bob the controller module next to the passenger seat is bad. Number 3 to put in your memory banks. I switched it out from one my other cars and both fans are running. All the diagnose tips here performed in some cases twice. Thanks everyone for your help!
07-24-2020, 05:37 PM
