I currently have a 1995 honda prelude w/ JDM h22a, my cooling fan doesn't work when and the car warms up, and idles for about 20min.., the temp... starts going past normal temperature. I want to know what i should do to figure out whats wrong and what sensors or switches need to be changed.

 

The first thing to do is check to see if the fan itself works by running direct power from you battery to it. If it works, then use a voltage meter to check and see if it's getting power through the factory wires. If that works then your thermostat is having a bad day or your heat sensor is.

Currently in the same situation, both my cooling fan and a/c fan took a crap on me.

 

might be one of the relays, i think theres 2 of them, i remember there was 2 on my 95 accord so im thinking theres should be 2 on prelude, good luch hope u find the problem

 

lukie still playing with this?

see in that second pic you posted, ECT SWITCH A (under the h22a caption), unplug the connector from that switch, use a paperclip and jump it - with the ignition at "on" (car can be running or not, up to you), when you jump the connector, you are basically simulating a "hot" switch, by giving low resistance thru the paperclip - this should engage your fan running. If when you jump the connector the fan does NOT run, chances are your fan relay is bad. it is in the underhood fuse relay box, and there are some tests you can do with a multimeter to make sure it is ok or not. if it is ok, start testing the fan itself (the method the guy above stated works, by directly connecting it to the battery).

between this post and the other, there isn't much more I can tell you about this system! haha. Just ignore what I said in the other post about the second switch that can run when your engine is off, because as you clarified you have a JDM engine - which usually does not come with that switch.


in any case good luck! just dive in there man.

 

okay i turned the key to the on position and jumped that connector witha paper clip with, also a wire nothing happened, so im going to buy a relay and try again


Modified by LukieLuc at 4:35 PM 6/13/2007

 

In the 2nd picture, is that hose, the bottom radiator hose?
if it is ive been jumping the wrong connector

 

it's the top rad hose so don't worry.

Gavz

 

okay i jumped the right plug, i heard the relay click and nothing happened, so i switched the fan and jumped it again, heard the click (relay working) and nothing happened
What does this mean what should be the problem?

 

did you directly test your fan by applying 12v battery ?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LukieLuc &raquo;</TD></TR><TR><TD CLASS="quote">okay i jumped the right plug, i heard the relay click and nothing happened, so i switched the fan and jumped it again, heard the click (relay working) and nothing happened
What does this mean what should be the problem?</TD></TR></TABLE>

Just like matt said above ^ run direct power from your battery to the fan. If nothing happens then your fan motor is shot.

 

i tested 2 fans
i just put a voltage meter to the fan harness and jump the plug heard the relay click on and 0 volts was going through it where do the stock fan wires go to inside the car?

 

so the fan did or didn't work with direct power?

 

the fan works with direct power and the relay works what, else couldnt be working. when i jumped the ect switch the relay clicked on but no power went through the stock fan harness


Modified by LukieLuc at 4:24 PM 6/14/2007

 

Try following the wires to make sure they haven't been cut or disconnected, check ground wire aswell. If your engine temp sensor is working then the problem is somewhere between the fan and the relay.

 

If the fan switch was bad would it do this?
they go behind the fender, do you know where they end up?

 

There's also a rad fan control module next to the ECU under the passneger side floormat against the firewall. It's a little black plastic box...might make sure it's plugged in and such.

 

oh okay i will check this out but, if the relay is working and the fan is working and everything is plugged can it be the fan switch?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LukieLuc &raquo;</TD></TR><TR><TD CLASS="quote">oh okay i will check this out but, if the relay is working and the fan is working and everything is plugged can it be the fan switch?</TD></TR></TABLE>

Sure, it could be.

 

I checked that control box (little black box next to the ecu) it was plugged i unplugged it and replugged it, so its connected i guess i will be changeing the fan switch, to see what will happen, what else might be the problem?

 

if you are jumping the connector and you hear the fan relay click but the fan doesn't RUN, however the fan DOES run when 12v is directly applied.

it is either the relay itself, or the wiring between the relay and the fan. I would say it ISN'T the switch (the thing that sits in the coolant stream), because obviously the problem is beyond the switch - from what you simulated by jumping the connector.

I think those relays have a little diagram on them (or maybe it's just in helms with the letter codes) but you can test the relay with a multimeter to make sure it's functioning correctly,

hope you solve it!, be sure to update when you get it figured.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LukieLuc &raquo;</TD></TR><TR><TD CLASS="quote">I checked that control box (little black box next to the ecu) it was plugged i unplugged it and replugged it, so its connected i guess i will be changeing the fan switch, to see what will happen, what else might be the problem?</TD></TR></TABLE>

I replaced my fan switch/sensor and my fan still doesn't come on. I know my relay is good based on my testing as well as the fan (turns on w/ 12V). One day decided to drive my lude w/ scanner connected to it to work (12miles). I noticed the temp that the ECU detecting saying 183-186degF. I figured it out that the service manual says that the relay doesn't close until the switch is sensing 203degF above. The only time i heard my fan turned on when I drove it for 5hrs and no wonder the fan turned on cuz it reached the temp threshold.

I don't really freak out now as long and I know I have a healthy cooling system no leaks no overheating. I think your ok. Just make sure that no leaks, thermostat is opening when it suppose to. I spent $50 eom from dealer and I think i just wasted it. I bought napa and It broke when i was screwing it in to the thermostat housing.

I am thinking making switch though from the relay so that I can make the fan turn on when I want to.

 

The thing is that since my fan dosent turn on, my temp gauge goes past half somtimes, & also on long trips when I drive to scholl, about 2hrs, the motor seems to loose performance since its soooo hot, I'm thinking that its the Engine coolant temp... switch "B" the one that's on the top radiator hose

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LukieLuc &raquo;</TD></TR><TR><TD CLASS="quote">The thing is that since my fan dosent turn on, my temp gauge goes past half somtimes, & also on long trips when I drive to scholl, about 2hrs, the motor seems to loose performance since its soooo hot, I'm thinking that its the Engine coolant temp... switch "B" the one that's on the top radiator hose
</TD></TR></TABLE>

I thought you had a jdm block though - in which case you wouldn't have a switch B? - I have a jdm block myself, and only the one switch (on the thermostat housing) - and I don't have overheating troubles. Funny though back when I was diagnosing my own cooling probs I ended up buying a upper rad hose housing that accepts a switch including a switch B (used), I thought I might throw it in there as backup - haven't got around to it though, and now I dont' really care for it, since my car runs cool.

 

Yeah, check out the fan switch. Get a multimeter and a Helms manual and start testing each wire like the book says. Once you've checked all the simple stuff that's what it comes down too

Have you bled the air out of the system recently?...might be another thing to check.

 

okay i went step by step to troubleshoot this problem i got up to step 9 where you connect terminals 2 and 4 and the fan worked so i went to page 22-9



Now i got up to step 3 where there was battery voltage, i do not understand what its telling me to do to correct the problem,



can someone put it in terms so a noob would understand?