Nicholbry

I've searched and found several threads regarding similar circumstances, but always with a different cause; so here goes......

Situation:
- 1990 S4
- Passenger side fan isn't coming on with: A/C on, 92 degrees and humid outside, temp gauge barely under the 3/4 mark.
- Driver's side fan sounds a little louder than I remember (like it's spinning faster than usual or trying to compensate).
- Driver's side fan will decrease it's speed periodically ("dip" in power) for a couple seconds and then back to full speed.
- I just had the fan out doing some mods for a better fit with C&R radiator that was installed last year.
- Connection between the fan motor outlet and the wiring harness appear to be clean, without any evidence of burning of the connectors, and not broken. I pulled it off and back on again just to make sure it was plugged in securely.
- Fuses #28-30 appear fine with no signs of melting/burning the fuse panel receiver like some others have reported.
- Battery connections look good.
- A possible clue?........A "click" followed immediately by another "click" noise (like the sound of a faint turn signal) could be heard in the passenger's area. This double clicking would occur with about a minute in between episodes. After about 15 minutes, the periodic clicking stopped. I know there is a "box" of some sort under the cover between seat and door sill. I haven't taken the cover off yet to inspect (difficult to come off for some reason and night fell).

Some initial questions:
- How do I diagnose this "box" if it is the culprit? Will it have obvious signs of damage?
- Does anyone know this part no. in the event I have to order one? I've searched my PET disc, but no prize yet.
- If a recommendation is to test the fan, can someone walk me through a detailed description of how to "jumper" things as I'm not familiar with how to do that? Sorry, don't mean to sound juvenile; I've just never been shown or adequately explained the process. I've got a 2-wire (with prongs) device with a light on it that is used to test electrical activity. I can also borrow my dad's voltmeter, but I'm not sure how to use it. Now seems like a good time to learn.

Thanks for any help you guys can be.

Jim M.

Check the fuses then swap the connections from the working fan to the inop fan. If it now works you know the fan itself is ok. Short of that I'm sitting in the hotel at OCIC and don't have acces to any of my manuals. There are detailed troubleshooting steps in the manuals to check everything else in the system. All you need is a VOM meter.

oz928s4

relay...was my problem

Nicholbry

Thanks Jim. I'll do that and see what I've got.

Oz928S4, which relay am I looking for? Is there a way to test the relay?

Thanks guys!

Nicholbry

Sourced the "clicking" noise to the fuse panel. I don't know if the relay or fuses are doing their job by this clicking noise because some other system isn't; or if the clicking noise is a sign that the relay isn't doing its job.

Alan

Neither of you have a relay for this...

The controller is the box by the passenger seat, the final drive stage is in front of the AC receiver/dryer (black fiinned unit with plug on the top).

Do as Jim says and swap fan wiring - if the opposite fan runs its a controller side issue - if the same fan doesn't run then its the fan unit.

Most likely is that its a fan issue. The controller runs the remaining fan at full speed if one fails. Normally both fans should be doing the same thing - both off, both half speed, both full speed.

The inside controller and final stages are actually very reliable units and rarely give trouble.

Alan

Nicholbry

Thanks Alan. I'm going to do as you and Jim suggested and plug the other fan up to see if I've got any action.

Nicholbry

Pulled the plug from driver's side and connected it to the pass. side. I let the car run for a couple minutes, turned on the AC and the fan does run. The fan isn't the problem....it's somewhere else.

It still could be the power lead to the fan, although it appears OK without any unusual wear marks.

The "clicking" noise at the fuse panel is still happening.

Alan

Check the fuses on the Central electric panel fuse 29 & fuse 30. If you have a voltmeter check the voltage on the bottom fuse terminal (you can probe directly into an indent in the bottom of the fuse - try it with the ignition on, running & AC engaged and also with ignition off).

Unscrew the retainer clip and pull off the plug to the fan final stage. Test the voltage on pins 1 & 4 (these go to the fuses above)

Alan

Nicholbry

Double checked the fuses...they're OK.

I'll borrow "the Pop's" voltmeter tomorrow as he is asleep (11:30pm here). Just to clarify (I don't want to short out something); you're saying go into the fuse receptacles (29 & 30) where the lower prong of the fuse plugs with the voltmeter? What reading am I hoping for?

Thanks for your help!!!!!

Alan

Don't just look at the fuses - test the with an ohmmeter (removed) or test with a voltmeter when is circuit - expect battery voltage at the top terminal and at the bottom terminal (on these particular fuses - not true for all...). compare to the red connections on top of the CE panel (thes also go to battery).

Alan

Nicholbry

I don't know if it matters or not, but my cooling flaps were zip-tied open a few years back by my mechanic.

Nicholbry

I checked out the system today as best I understood your instructions:

Final Stage:
Pins 1 & 4 w/ ignition off (achieved a reading)
Pin 3 with ignition on per "troubleshooting" instructions in WSM (achieved a reading)

Fuses:
#29 w/ ignition off (55) & on (62)
#30 w/ ignition off (55) & on (60)

Wire receptacles @ fan
got reading with the ohmmeter on one terminal (per fan).....including the fan that isn't coming on.

Alan

Can you be clearer what and how you are measuring - the ohmemter mode is for use on the removed fuse (and possibly on the disconnected fan) only. Use voltmater mode for all others - what volts are you measuring? what do (55) (60) (62) mean ? makes no sense?

I'm still not sure if both fans can be made to run seperalty if connected to the working controller? seemd that was the case. Please be very clear what you have done... you can check

The flap controller is not related to these symptoms - as long as the flap motor was unplugged or the fuse removed zip tying it open is fine and anyway it makes no difference to the fan operating mode.

Pin 5 & Pin 8 on the fan final stage connector go to the fan plugs - the other pin on each plug is ground - you can check this wiring (use ohmeter, from final stage plug pin to fan plug pin)

Alan

WallyP

Nicolas,

My apologies if this is stuff that you already know.

A multimeter measures electricity in several different modes.

Ohmmeter - measures electrical resistance between the probes. This is used on disconnected parts of a circuit only, and NEVER with power on the circuit. The different resistance ranges are for low resistance up to very high resistance. You will almost always use the lowest range, usually Rx1 or Rx. You use this to check for continuity and for resistance between the two points. Continuity is whether the circuit is complete between the two points being tested, and a compete circuit will be shown by a low resistance. An open (broken) circuit will be shown by infinite (maximum) resistance, and sometimes by "OL" (Over Load) on a digital multimeter.

Voltmeter - measures voltage in either AC or DC in several ranges. For automotive use, you will almost always use the lowest DC (Direct Current) range. The maximum voltage that you will see on the primary (low voltage) circuits will be 15 or 16 VDC (Volts Direct Current). With the engine not running, you will normally see 12 - 12.5 VDC if you have a good circuit. This voltage is almost always measures with the red probe on the circuit to be checked, and the black probe on a good chassis or body ground.

For the checks that Alan wanted you to make on the fuses, you would put the multimeter on the lowest DC voltage range (provided that the lowest range will read 15 VDC or higher), put the black probe onto the ground connection above the Central Electric Panel (bolts with a bunch of brown wires), and put the red probe tip into the upper tiny indentation in the face of the fuse for the fan and touch the metal there. You should see battery voltage. Then put the tip of the red probe onto the metal inside the lower indentation in the fuse. If you also have battery voltage there, the fuse is good.

Hope that this helps!