Radiator & Condenser Fans not coming on

[AdamJB]

2000 Honda Accord LX, 2.3L I4. Just replaced original engine with an engine from a 1998 Accord LX. (Original engine overheated and blew while my teenage son was driving it.)

My problem is this: The radiator fan and condenser fan do not come on once the engine warms up (water temp > 199 deg F.) The AC system can turn both fans on, so I know the fans, fan wiring, and relays are good. I just installed a new fan radiator switch, which did not help. I also removed the thermostat housing after warming the engine up and verified that the thermostat had opened, so I know the thermostat is good and is letting water past to the radiator fan switch.

I am now thinking it is an electrical problem with the radiator fan switch wiring. I bought the Honda shop service manual for the car and am attempting to check the wiring.

One question I have is what is meant by the term "Body Ground"? Does this mean a wiring ground point like G201, or can "Body Ground" mean anywhere on the body?

Does anyone have any other ideas for me?

Thanks!

 

[kn0x47]

body ground means the ground wires attached to the frame of the car. are you sure the AC is supposed to turn both fans on? normally only one is for the AC

 

[AdamJB]

Thanks for the quick response and for the clarification on "body ground".

Yes, the Honda service manual indicates that both fans are activated by the AC system as well as the radiator fan switch.

Testing connectivity to Body Ground at G201 on fan switch connector terminal 1 is good, and I get battery voltage on terminal 2. I just tried jumping the two terminals on the radiator fan switch connector, and both fans come on when I do so. So the wiring is all good.

I thought maybe an air pocket could be preventing water from contacting the inside temp sensing surface of the fan switch, so I used the air bleed valve on the thermostat housing to clear air. I then removed the fan switch, poured in coolant up to the level of the hole and screwed the fan switch back in.

Still no luck. =(

I also heated the engine up to 230 deg F (as indicated on my scan gauge) and tested connectivity between the two terminals in the fan switch. No connectivity. It should close the circuit by the time I pass 199 deg F.

Seems to me everything indicates a bad radiator fan switch, but what is the chance of both the old one and a brand new one being bad?

 

[kn0x47]

i wouldnt think the new one would be bad but you could always take it back to the auto parts store and get a new one under warranty. sorry i dont know much about trouble shooting the coolant system

 

[Igor]

Both fans turn on for a/c...but if the switch was bad I don't think it'll turn on at all? I could be wrong...does the car overheat? Maybe it's running cool enough for the fans to turn on. I hardly ever hear my fan turn on (while running a/c yea or hot summer day) during normal driving . What does the temp gauge read? Moves up/down? Check engine light on?

 

[Igor]

In my civic I had the fan wired to where it was on at all times, once turn the ignition to on position, but in the winter time you might not get any heat for that reason, it'll run too cool. Temporarily you can wire it to stay on at all times (just so u can get places)

 

[LeBirdNest]

I still think it's the thermostat... Mine looked fine but wasn't actually fine. Are the hoses pressurized? If not, your thermostat isn't working. If you're overheating then is change the thermostat. If you're not overheating the fans will come on as soon as the thermostat in fact opens.

 

[AdamJB]

The radiator is holding pressure. I have verified that the thermostat is opening up and letting water into the upper radiator hose. I have run the engine until my Scan Gauge reports 230 deg F. Fans should come on before it gets to 200. My old engine always ran around 185-200 deg F. I suppose it's possible that the new engine's water temp sensor is giving me an artificially high reading, and that I'm not letting the engine get hot enough. I'm going to test the old and new fan switches tonight by suspending them in heated water and measuring the temp with a thermometer. Over about 196 and they should close the circuit. I also forgot to mention that I've tried two thermostats as well; the one from the old engine, and the one that came with the new engine. I'll also do the water temp test on the first thermostat I was using.

 

[FNCONE]

i know you said you checked BUT JUST INCASE.
Turn on your heat when u reach normal running temp... then check if you have anti- Freeze.... (obviously be careful) when i did my swap my fans weren't coming on, i added anti freeze,... almost over heat and NO fans. i turned on my heat and almost had to add another bottle of anti freeze....
just a thought you never know.