accord96lx

Just replaced a radiator and going through the steps the owners manual says to run the engine until the radiator fan cycles twice, but it never does..not unless the AC is on.
Maybe this is why the radiator started leaking.

What are the right steps to take to figure out why the fan doesn't kick in when the engine is hot?

poorman212

First, that should be "fans" as in BOTH fans running.

Next, can we know what engine is in the car - 4 or 6 cyl?

accord96lx

Yep its a 4 cyl 2.3L Ulev Vtech.
2000 Accord 4 dr SE

The coolant fan I mean isnt working, the Owners manual said on step 13 of replacing the coolant to " Start the engine and let it run until the radiator cooling fan comes on at least twice. Then stop the engine"
Thanks for helping!

poorman212

Fan or fans....cooling fan or condenser fan. You have A/C so the car came from the factory with TWO fans.

When you turn on the A/C do BOTH fans come on?

Next, when you are letting the car idle, how long are you doing this? Depending on where you live and the time of year, it could take ~20 minutes before the FANS cycle - there are other factors that can play into this.

What is the temp gauge showing as the car is at idle for the time you are giving it?

How did you go about bleeding the cooling system when you replaced the radiator?

accord96lx

Yep, both turn on when the AC is on


At first I let it run 20 min, I Live in Georgia it was about 70 degrees in the sun.
Then I took it on a drive about 6 or 7 miles and while the car was running popped the hood and saw the fan was not on. I turned on the AC and it came on with the condensor fan.
The temp gauge reached close to the midway point (40 degree angle ish) on the dummy gauge when it was at about the 1st or 2nd mile.

I followed what the Owners manual said, step 8 "Loosen the bleeder bolt on top of the engine. Pour coolant into the radiator. Tighten the bleeder bolt when coolant comes out in a steady stream with no bubbles."

The bleeder bolt on top of the thermostat housing is one I opened. Hopefully in a radiator replacement situation that works just as well as only replacing coolant as the owners manual could tell me.

poorman212

Sounds pretty normal to me....the gauge never made it to half.

Turn the key to on. Turn the A/C off, set the heat to max, turn the blower motor off. Start the car and let the darn thing idle, keep an eye on the temp gauge and if it ever gets to 3/4 without the fans cycling turn the engine off. Let the thing idle until either the temp gauge starts to climb above the half mark or the fans cycle.

I honestly think you just didn't let it run long enough and everything is fine. Test it out and be sure.

accord96lx

I did as you mentioned and let it idle 20 min and still no fan. I have even driven over 50 miles and in heavy traffic and popped the hood when I got to my destination with the engine running and the coolant fan was not on.
The temp dummy gauge never went above the halfway mark...stayed just above 1/3 of the way.

I took a look at this video even though its about a civic to see how the diagnosis non-working radiator fan.
I then checked the cooling fan relay by taking it out and attaching a mini jumper cable from the battery and used the alligator clips to attached to the base prongs that insert into the fuse box. I connected one lead to one of the prongs (the ones parallel aligned) with the neg lead and when tapping the other cable that was hooked up with an alligator clip to the pos cable there was a clicking sound inside the relay. From that I was told you could tell that the switch is fine. I had also switched out the cooling fan and ac fan relays just to see in the 20 min idle test and no cooling fan engaged.

I also used a metal paper clip to jump the coolant fan switch on the housing and the fans would kick in when the key was turned.
One thing I havent done the OHM testing on the switches which Im not all that knowledgeable of, and the temp switch that he shows on the civic thats near the exhaust manifold...I dont know if my Accord has one there but that I havent tested.

accord96lx

I attempted to test resistance on the fan switch using a multimeter and Im not sure what to make of this.
The instructions say to set to the lowest OHM setting which on my MM says 200.
So I set it to 200 ohms and with the engine cool disconnect the connector to the switch and take the black and red probes and touch the 2 prongs...red on one and the black touching the other and the reading shows 1.
According to the instruct that would mean an over range and to switch to a lower OHm setting, but that is the lowest.
Does this mean the switch is bad, or that I dont know what the heck Im doing? Or both?

holmesnmanny

You have to heat up the switch and around 195 degrees or so the switch will close internally and you will have zero ohms of resistance. If you have a "beeping" function you can just use that instead. It will beep when the switch closes so basically you'll suspend it in boiling water.

accord96lx

Thanks, I ended up replacing the fan switch today and took it on a 10 mile drive and the coolant fan still doesnt kick in, not unless the AC fan is on.
What should I try next?

poorman212

Get a scanner that can read live data and see what the PCM thinks the temp is.

Again, leave the dang thing sitting there idling away until either the temp gauge goes to ~3/4 or the fans come on - make sure the blower motor is turned off.

accord96lx

I think ill get this scanner based on reviews its gotten. Seems decent and not super expensive.

I had been watching the fans after I had been driving for over 30 miles or more in 83 degree heat.
Id pop the hood with the blower motor off and didnt see the fan come on. But I had only popped the hood and looked for maybe a min and closed it down.
If I had left the dang thing sitting as poorman212 suggested I would have probably seen the fans eventually kick in.
Reason I say that is because what I ended up doing was headed to a junkyard and bought the sensor connector so I could hook up the multimeter and test the ohms out and all to see if the coolant/engine temp sensor was operating properly.

1. Drive around again, this time maybe 12 miles
2. Disconnected the coolant temp sensor
3. Connected the cut off sensor connector from the junk yard
4. Set mutlimeter with alligator clips onto the exposed wires of the junkyard sensor connector and checked resistance with switch set to 2k
5. Got a reading of .227 and it steadily climbed to around .244 when suddenly both fans came on
6. Then the resistance began dropping to around .164 and the fans stopped
7. And it was cycling the same way up and down and fans going off and on
8. I disconnected the dangling junk yard test sensor clip and reconnected the sensor connector thats part of the wiring harness
9. Took infrared thermal gun and targeted metal housing on the engine thats attached to the upper radiator hose
10. When fans weren't running the temp rose to 197 and the fans came on
11. temp dropped and the fans stopped

I was happy to see the fans working and assumed the coolant sensor was good, but what puzzles me is why the temp sensor would still work and send signals to fans when I had disconnected the main engine temp sensor and put on the dangling tester clip for the junkyard.
I assumed the wiring harness would have to be connected for the signal to get transferred.
I guess all is well, fans are working but still confused how the engines temp cycling could happen with a disconnected engine temp sensor from the wiring harness.