Noob@Cars

Hi, Sorry to ask this question, I looked around on this 90-2002 accords, & couldn't find the answer i was looking for, If it has been answered - sorry for asking the ?..I dont know anything about cars, let alone the ? im about to ask..My apologies

I recently installed the passenger side radiator fan, because my car was overheating & i realized that the motor & fan blade came off while i was driving, dont know how - but it came off completely & hanging in between engine & radiator, The new fan comes on, but i also noticed that the other fan [AC] doesn't come on at all, My ? is...Do both fans suppose to come on when the car overheats? I know the passenger side does, but the other one doesn't, Also, since its an AC fan does it come on only when you turn on the AC or is it also suppose to come on when the other fan is on, regardless if AC is on/off...

thanks in advanced

holmesnmanny

It comes on when the ac comes on.

Lost Again

AC off- BOTH FANS should come on when the car is running and thermo a (t-stat) reaches ~194*....so if the car is running, ac off, and only the one (pass side) comes on...something IS wrong....fuse, relay, motor on the drivers side...the ONLY time one fan runs on this gen Accord is when the car is OFF

Lost Again

Maybe yours has had an issue since you owned it, not sure. We can test if you want

Just last night after replacing the PS pressure hose on an 89 Accord (LX auto) I watched it from cold start up, when it got warm....BOTH fans came on. My 5th gen does the same.

poorman212

OP-the year/engine might help.

But IMHO-"Lost" is correct. AC off, car running in driveway (or what ever) BOTH FANS should cycle on and off as the temp gets to the proper level.

Holmes-according to the wire diagrams and testing I have done, your 91 should be the same. If you need help in tracing the issue let me know and I would be glad to help or maybe the attached will help....notice how thermo a is tied to both the ac and cooling fan realys....again if I can help let me know.

holmesnmanny

Actually I really don't know to properly read an electrical diagram. So if you want to describe what's going on, that would be good information for everyone.


Edit: editing out junk

Lost Again

Holmes-since the op hasn't come back, this might be more of a conversation between us.
If your point was that they both come on when the ac is on-yes I agree and that is true, reading just that part. I NEVER said one fan runs when the ac is on....my point of wrong information was to when the AC is OFF

However, to answer the real question as asked (as I read it) -AC off (as stated originally in my post-no edits to date) -when thermo a gets to the proper temp (usually ~194* on the 4th and 5th gens-not 100% sure on the 6th). BOTH fans should come on.

I will admit to this, I didn't mean to sound like an a** in what I posted. But at the same time what I posted is true, AC off, temp on thermo a gets to ~194* BOTH fans should come on.

I think both of us read each others post wrong. You said both run with the ac on (yes). I said that BOTH run when ac is off and the temp gets to the set level (yes).

Lost Again

Well, let me see if I can break this down.

First a few assumptions. I’m using the diagram from this 91 Accord (4th Gen), others are similar; but, may differ slightly. To start with we will assume we are looking at this when the AC is off and ignition is ON/position II.

++++I’ll start with the Radiator fan relay which controls the “Radiator Fan Motor”.
The Yellow wire should be hot (+) going into the relay, this comes from the Ignition switch, thru the under dash fuse panel (#8 - 7.5 amp). The *White (*=assuming color based upon memory/history-not listed in the diagram posted by poorman212) wire should also be hot (+) at all times since this is coming from the under hood fuse panel (#39 - 15 amp).

When Coolant Temp Switch A (Thermo-switch A located on/around the t-stat housing, lower radiator hose) gets to around ~194*, it closes allowing ground to be passed from ground location G101 thru the switch to the Blue wire into the relay. Thus creating the ground to the coil/magnet inside the relay (+ is from the yellow noted above). Once that coil is activated it pulls the relay closed. This allows the power (+) to flow from the *White wire into the relay thru to the BLU/BLK to the actual Radiator fan motor. Ground for the fan motor is thru G201. So you now have 12v in (BLU/BLK) and ground (BLK) at the motor.

++++So now to the Condenser fan motor relay….nothing has changed from the above conditions/assumptions.
The YEL/WHT wire should be hot (+) into the relay, this comes from the fan controller. The White is also hot (+) at all times into the relay since this comes from the under hood fuse panel (#29 - 15amp).
With the Coolant Temp switch closing at ~194*, it allows the ground to flow to the Blue wire of the relay. Thus, closing the relay which allows 12v to flow from the White wire to the BLU/GRN that goes to the condenser fan motor. Ground for the motor comes from the Black wire and ground location G281.

So when the coolant temperature at the thermo-switch A is ~194 degrees; both radiator fan and condenser fan should turn on. You can also test whether your two fans work, first with the engine off, disconnect the green connector on Thermo-switch A, jump the two terminals on the connector (not the thermo-switch) together with a small paperclip or wire, then turn the ignition to ON to see that both fans operate. If the fans works; but, they don’t come on when the coolant temperature is ~194 degrees, then you may have a faulty thermo-switch A.



-----------Changing the above conditions. Now the AC is on (assumption here is that you have a functioning AC System).
So the next question. How do they BOTH run when the AC is turned on? Basically, thru the same process. Instead the ECU is applying the ground thru the Blue wire which again grounds BOTH relays (radiator and condenser) allowing power to flow to the fan motors.

----------Changing conditions again. Now the key is OFF.
Then the last question I can think of. Why does only ONE fan run when the key is turned off? This time Coolant Temp Switch B (thermo-switch B-upper radiator hose) is “in play”. If Coolant Switch B detects temp above ~226* it closes and sends a ground signal to the Fan Timer thru the WHT/GRN wire. I’m not going to get into the internal workings of the fan timer (that is a can of worms in itself). But basically it sends a ground to the same Blue wire closing the Condenser fan relay.
You may ask why then doesn’t the Radiator fan relay do the same thing. Well, you have to remember that the 12v to the “coil” of that relay comes thru the Ignition switch which is off….therefore the relay will not close.

To recap: This is for cars with a working radiator fan and AC condenser fan. Whether the AC is on or not, if the coolant temperature reaches ~ 194 degrees and Thermo-switch A is working properly (switch on or near thermostat housing), both radiator and AC condenser fan should turn on.

When AC is on, even if coolant temperature at thermo-switch A is below ~ 194 degrees, both radiator fan and AC condenser fan will be on.

When the car is turned off, if the coolant temperature near Thermo-switch B is ~226 degrees, the radiator fan only should turn on and run for a short period of time.

Anybody that wants to butcher this or me…have at it.

Holmes said it might help, so that is what I’m trying to do.

And a BIG Thanks to a friend of mine for reviewing this and adding a few points for additional clarity.

holmesnmanny

Thanks for the info

Tbh, I'm too tire to absorb it tonight, but tomorrow I'm going to try to understand it in full. I plan on taking an electical class at my college sometime soon.

Tonyneedshelp

Thank you for that great write up Lost Again.

I'm wondering for the sake of learning more and eliminating any confusion on my part.

Would it be safe to assume one of two things for the following condition for a 4th gen accord?

If only the Cooling fan comes on "no condenser fan activity" when the car is running and knowing that both fans work when jumped with both + & - 12v directly from vehicle battery:

1: It could be a bad ground to the condenser fan Circuit
2: Or thermoswitch A is not working and thermoswitch b is running only the cooling fan because the coolant level is @ or above 226F while the car is running

poorman212

Tony-I'm a bit confused by the description?

Key on, ac off, jump the wires to thermo a, BOTH fans should run? If only the pass side/cooling fan run then the condenser fan circut is in question,,,,,fuse, relay, timer all of which are for this fan...different than the cooling fan....driven by the same ground (thermo a) but travel different circuts to get there.

Thermo b has no tie to the cooling fan (besides sharing the same ground G101). So simple (OE config)- thermo b has "no control" over the cooling fan.

celtickaro-2012

If the radiator fan not turning off, when ignition switched is off for 30 minutes, what is the problem?

Lost Again

"My guess", you need to test the fan timer.....of course I have no idea what year you are dealing with

Pretty good info for the 4th gen here

http://techauto.awardspace.com/overh....html#Fantimer

RayIII

By the way just where are the cooling fan circuit ground points, especially G101 - I'm actually interested in ground point for a '97 Accord.

GhostAccord

G101 for the 97 is located on the upper intake plenum on the driver side end. It is secured under one of the vacuum tree mounting bolts.