Hi everyone.

I got a problem. First off its a 97 sedan d16y7, model DX (its a canadian-spec EX, but as far as I understand its the same as a US-spec DX)

Anyway, the cooling fan does not come on. Here is what I've done to troubleshoot.

connected fan direct to 12v - fan itself works. I re-connected it to the harness, and tried swapping the relays around (I suspected a bad relay as a possibility?) with no change. Changed the thermostat (for maintainence sake) and fan switch (located on thermostat housing) with no change. However, if I put a jumper in the "pigtail" or socket that plugs into the fan switch, the fan comes on - and runs when ever the ignition is in the "run" position, even with the engine not running. The fan does not cycle on/off like it should.

I'm stumped. The only thing left that I haven't tried (that I can think would help) is replacing the socket/pigtail that plugs into the fan switch - by pigtail I mean the socket with 2 wires that lead off into a bundle of wires under the hood. Other then that I'm out of ideas.

Can anyone help me?

Oh yeah, I do have an engine light on but I know what the cause is (bad cat/cracked exhaust manifold). I have not checked for any other codes.

Thanks in advance!

PS . can post pics later if needed for clarity. Just ask

 

Does the engine overheat?

No -- don't worry about it.

Yes -- Test drive with the switch jumped so the fan runs all the time. If it still overheats, there is another problem.

 

mk - nope, no overheating. Its totally driveable with the jumper in. Really, the biggest thing that bugs me is that I have yet to nail down what the problem is (I hate being stumped by something that should have been an easy diagnosis).

My best guess is that the pins in the fan switch are not making proper contact with the pigtail.... I guess I'll get a new pigtail, and see if that solves it

 

So it does overheat with everything set up like stock (switch plugged in normally)?

Normally, the fan doesn't run much except for city driving in hot weather. The fan is activated by the temperature of coolant leaving the radiator not the engine temperature.

A bad connection is about all it could be, or your new switch is a dud. You can test the switch by putting it in hot water (just the bottom part, try to keep the terminals dry). I think it is supposed to close at 140 degrees.

 

well, according to the dash gauge, it stays in its normal spot. It does not climb any higher. However if I am in stop n go traffic, it will start bogging when pulling away from a light. However once the RPMs climb a little bit it smooths out somewhat. However with the fan "jumped" as I currently have it, I have no issues.

I'm fairly confident that the problem is the socket is not making proper contact with the pins on the fan switch. I'm guessing that by jumping it (and it coming on right away) I've tested pretty much everything else in that circuit.

by jumping the socket/pigtail, I immediately made the assumption that the switch itself had failed. Perhaps because installing the new one, the problem is elsewhere (or like you said, the new one is a dud)

I'll try to tinker with it again in the next few days and report back...

 

Don't try to fix a non-existent problem.

 

Ron, the problem is not solved yet. Yes the fan runs now, but only because I put a jumper in the pigtail/socket. If it is plugged into the fan switch, the rad fan does not come on at all, which leads to overheating symptoms.

As I stated I will try to test the fan switch in the next few days and report my findings. If the switch itself is defective, then I will replace it. At this point I think it is the socket, but I was hoping someone here would have an idea I overlooked or a solution. As of yet no one has come up with anything I have not thought of so I will continue testing, and report back when I discover more.

At least then maybe some other reader will have some info to go on, if they happen to run into the same situation.

 

I did not see that you ever mentioned an overheating problem until now. Bleed the cooling system and, if the problem persists, then replace the ECT switch on the thermostat housing.

 

cooling system has already been bled. The ECT you refer to is probably what I have been calling the "fan switch" in my posts - I didn't know the correct/technical term for it. I did replace it (2 pin round connector located on the thermostat housing - correct?) however the problem still persists.

I have disconnected the harness to the ECT/fan switch and installed a jumper. The fan DOES work (and because it works I am making the assumption that all other components including relays are functioning as they should. If I am wrong on this please correct me). With the jumper installed, the fan does run at all times whenever the ignition is in the run position, with the engine running or not. However because the fan does not work when connected to the ECT (either the old one or the new one) I am making the assumption that the problem is that the pins in the harness do NOT make proper contact with the pins of the ECT. That is one option. The other option is that the old ECT had indeed failed and the new one I installed is a dud.

I will test the new one this way (based on how I figure it works):

When the system is cold, the switch is open, and if tested with an ohm meter, there would be no conductivity. However once it reaches a certain temp (mk posted 140F) the switch closes, thus completing the circuit and turning on the fan.

(again, if I am wrong anywhere in my diagnosis or assumptions, please correct me)

So if I test it "cold" there should be no conductivity. Once warmed up the switch should close, and when tested with an ohm meter I should see conductivity (correct?)

Yes the car runs fine with the jumper (its summer, better to run cool then hot) but I would prefer it to work as it should.

 

ok, so I checked the resistance of the ETC with the car cold, and then with the car at normal operating temperature. There was no difference. Does this indicate a bad ETC?

I also checked the voltage at the socket. aprox 7.5v. Should this not be closer to 12v?

Also, my AC is not working (dash light comes on, but no AC) I didn't really know where to start checking. However in my poking around, I found a 4-wire harness bolted to the AC fan. If I used a test light (connected to ground) to probe the 4 wires, one of them - I don't remember the color of the wire or the position on the harness - would trigger the AC to work. (Compressor turns on, AC fan runs)

Are these 2 issues possibly related? The rad fan issue only came up recently but the AC was not working last year already and I just never got around to looking into it