Normal Cooling Fans Operation ???

SevillianSTS · #1 (**permalink**) 08-28-08, 05:52 PM

99 Seville STS
When car is hot, idling, and I turn on AC Pass side fan turns on, and driver side barely spins, it just barely rotates. If I rev motor a little for a moment, they both seem to run on high.

Does this sound normal?
Do these fans ever run independently?

I have a feeling something is wrong with the low speed on my driver side fan. If so, would that be in the motor, or a relay?

I know I could just run a jumper wire to the fan motor, but wouldn't that just run the fan on high... which it already does now.

Basically, how should these fans individually run normally?

SevillianSTS · #2 (**permalink**) 08-28-08, 06:35 PM

Just checked out my buddies 2000 STS

Turn on the AC at idle and both fans come on low.

Rev the motor for a second and they both go onto high.

How do I confirm the low speed on my driver side fan is not working? and would that be a relay or the fan motor itself. As mentioned before the fan does rotate when the other side starts, but it just barely rotates.

Thanks in advance...

JimD · #3 (**permalink**) 08-28-08, 06:42 PM

I can tell you how my '98 Seville's fans operate; and it's safe to expect no difference between '98 and '99.

With A/C ON, both fans operate at LOW speed (powered in series); I have monitored the fan motor voltage to confirm this. The fans are always ON when A/C is selected to guarantee airflow across the A/C condensor during stop-and-go traffic and parking lot situations.

With A/C OFF, the PCM controls the operation of the fan motors as a function of engine coolant temperature. When the fans are needed for heat removal, they are both spinning; usually at LOW speed but also at HIGH speed if required.

I find it necessary to use a flashlight to confirm the fans are spinning because my ears cannot pick the fan noise out of the other under-hood noise.

**Ranger** · #4 (**permalink**) 08-28-08, 06:57 PM

If I am not mistaken, to add to what JimD said, WITHOUT the A/C on the fans will run at low speed when the ECT reaches 224 degrees and kick on high at 229 degrees.

SevillianSTS · #5 (**permalink**) 08-28-08, 07:03 PM

If they are powered in series, if i unplug one, shouldn't the other one stop.
Because one will run if you unplug the other.

Sounds like my low speed is not working on the drivers side. Can that be caused by a relay, or is that in the motor?

Thanks

**Ranger** · #6 (**permalink**) 08-28-08, 07:07 PM

Just guessing, but I would think that is the motor.

JimD · #7 (**permalink**) 08-28-08, 07:15 PM

Quote:

Originally Posted by SevillianSTS

If they are powered in series, if i unplug one, shouldn't the other one stop.
Because one will run if you unplug the other.

Sounds like my low speed is not working on the drivers side. Can that be caused by a relay, or is that in the motor?

Thanks

The motors are powered in series for LOW speed operation. For HIGH speed operation they both see full system voltage.

You have a failed fan motor (or faulty connector - wiring) if you can see "one will run if you unplug the other".

submariner409 · #8 (**permalink**) 08-28-08, 07:35 PM

Go into the underhood fuse box and find the three (?) fan relays......12V power and series/parallel operation relays. They determine fan speed and sequence. 2 fuses also.

SevillianSTS · #9 (**permalink**) 08-28-08, 09:50 PM

They both will run on hi no problems, its just when you first turn on AC only the pass. side turns on low, and the driver side just sputters around.
If I unplug the "good" pass. side fan, then when I turn on the AC the driver side will run on high.

Once I locate the relays anything I can do to check them, can I switch them around to troubleshoot?

Just want to confirm things before I spend a 100 bucks on a new fan/motor.

Thanks again

submariner409 · #10 (**permalink**) 08-28-08, 09:57 PM

IF your car has 2 fan power relays and one parallel/series relay, the power relays can be swapped to see if there's a burnt contact. The parallel/series unit is a different pinout, so it is a standalone relay.

SevillianSTS · #11 (**permalink**) 08-29-08, 09:09 AM

If the low speed is controlled by the series relay then I guess there is no swapping of relays to troubleshoot.

What would you guys do first. I know a relay is cheaper than a $100 fan/motor, but would you just buy a fan, or change relays first ???

William Miller · #12 (**permalink**) 09-28-08, 11:51 AM

I'm having simular problems with overheating while at idle.
You can bench test the relays. There is a diagram printed on the side of the relays that show which terminals are for the coil and which are for the contact.
If you connect the coil pins to a battery, you should hear it click.
If you connect a ohm meter or one with a continuity test, you can confirm the contacts are closing when you hear the click.

The black relay has 5 pins. The extra pin is the normally closed contact on the relay. With now power to the coil there should be continuity across this pin. When the coil has power, this pin will lose continuity and the other pin will get it.

I do have one question: It seems like the grey (4 pin relays can be installed upside down.) My guess is that id doesn't matter. Can someone confirm this?
If it does matter, which is the correct way to install them?
Thanks!

submariner409 · #13 (**permalink**) 09-28-08, 12:15 PM

The 4-pin (on/off) relays are not pin sensitive because of the diagonal internal connections. Of course, concours requires that all the lettering be oriented the same......

If you want to test your fans, the sockets are hot even with key: OFF, so you can use a short piece of 18 ga. copper wire to jumper across the hot pins. Each fan should run in fast because they're not in series with no relays in place. Use pliers to hold the wire: those fans draw a lot of current and even 18 ga. will get hot. Ask me how I know.......

SevillianSTS, I know this is a month old, but after going back through this thread twice it sounds as if the parallel/series relay is on its way out. Still $30 or so at the dealer......

William Miller · #14 (**permalink**) 09-28-08, 01:13 PM

Quote:

Originally Posted by submariner409

The 4-pin (on/off) relays are not pin sensitive because of the diagonal internal connections. Of course, concours requires that all the lettering be oriented the same......

If you want to test your fans, the sockets are hot even with key: OFF, so you can use a short piece of 18 ga. copper wire to jumper across the hot pins. Each fan should run in fast because they're not in series with no relays in place. Use pliers to hold the wire: those fans draw a lot of current and even 18 ga. will get hot. Ask me how I know.......

SevillianSTS, I know this is a month old, but after going back through this thread twice it sounds as if the parallel/series relay is on its way out. Still $30 or so at the dealer......

Thanks for the confirmation on the 4 pin relay (It doesn't matter!)
Since the 5 pin relay has a normally closed contact, Is that for the (in series mode or parrellel?

Can you give me a breif description of how the circuit work?

submariner409 · #15 (**permalink**) 09-28-08, 01:40 PM

OK......2 fans, each with its own 30A (?) fuse and relay feed. If each fan is commanded on in FAST (engine temp at 236 or transmission temp at 304) then both Fan 1 & 2 relays close, the P/S relay is de-energized, and full system voltage goes to each fan. If fans are commanded ON in SLOW, (temp at 224 or A/C ON) Fan 1 relay closes, the P/S relay closes, thus creating a series circuit through the 2 fans, so there's a voltage drop in the fan circuit which causes the fans to run in slow. It's 12V to Fan 1 to Fan 2 to ground.(Exactly the same setup as the DRL circuit which commands the high beams ON in series.)

(I spent a lot of lunch time in the crossroads store/restaurant in Darnestown - High speed River Road run toward Seneca then lunch - grew up in Chevy Chase, right at the Circle. Used to keep a couple of horses down at Calithea Farm on River Road....))