JZ Hydro fan help please Running full blast

[Heggy]

Can't seem to get the fan to calm down, running at full blast. If I disconnect the fan ECU it slows down to "idle". I've checked the components as per below. Am I missing something?

Pin # Dest
1 IGNITION (actually 7.5 AMP PWR, rewired to B1-16 + 12V) (checked OK)
2 SOLENOID + Part of swapped JZA70 harness (Has resistance reading across pins and slows when ECU not connected)
3 SOLENOID - Part of swapped JZA70 harness
4 GROUND Part of swapped JZA70 harness (checked OK)
5 IDLE ECU Part of swapped JZA70 harness
6 TACHO IGNITER Part of swapped JZA70 harness
7 COOL AC ECU not connected. Tried grounding, have not tried +12V
8 AC HIGH PRESS SWITCH not connected
9 TEMP SENSOR+ Part of swapped JZA70 harness Measured 42K ohms between 9 and 10
10 TEMP SENSOR - Part of swapped JZA70 harness Measured 42K ohms between 9 and 10

 

[Nick M]

Isn't the solenoid supposed to allow more hydraulic fluid, and subsequently more fan speed when hot?

 

[Heggy]

Yes. The fan runs full speed all of the time, hot / cold / medium.

 

[Nick M]

I am going to make an assumption since you posted a JZ question outside the JZ section. The solenoid moves a spool valve allowing the passage of fluid. I would have to see it or the schematic and strategy from Toyota to know for certain. If that is what it does, then the spool valve is stuck open. A spool valve is just a name given to valves that open and close to allow hydraulic fluid of some sort to pass through.

 

[Heggy]

I'd agree that is a possibility if the fan ran full speed all of the time, however it is normal (slow speed) with no ECU.

 

[scottiedawg66]

You are on to something there heggy. My fan runs full blast even with the fan ecu disabled, so I think I have the stuck solenoid described above. I think your issue is electric. Have you tried a different fan ecu?

 

[Heggy]

No I have not, however I did start the engine in the clip and the fan was "idling" (running at a low speed) so from that I assume that it was (or should be) working.

 

[Radial]

The Hydrofan ECU has a very simple task - Start the fan when the radiator is hot.
It's got its own temp.sensor on the radiator itself for this, usually on the RH side of the radiator.
Is this the one you checked? It does not use any of the sensors on the engine itself. It's got its own on the radiator.

If this sensor is disconnected or broken (no continuity), the hydro-ecu thinks your engine is boiling hot, and gives you all the cooling it can.

so, take a deep look at the temp-sensor and check for continuity in wires and sensor.
5 cents on a broken temp-sensor, broken wire (very common on old wirings), or heavy corrosion somewhere on that circuit.

Solenoid is probably just fine, as it stops when ecu gets disconnected.

 

[Heggy]

In my original post the temp sensor (L/H SIDE LOWER RAD) measures 4 K approx. Infinity when plug removed.

 

[Radial]

Hmm..you are measuring at the Fan ECU pins right? 4K ohms at cold engine?

 

[Heggy]

Yes between pins 9 and 10 on the Fan ECU connector

 

[Heggy]

I hooked up ohm meter across pins 9 and 10, reading was 88K (sorry forgot it was on the 20k Scale). Started the engine, took it for a quick drive and as the water heated and started circulating the resistance dropped to 42k ohms. From this I would assume the temp sensor in the rad is working (don't know what the value should be, but the resistance decreases as temp increases).

 

[Radial]

Yeah, the fact that it is changing in resistance suggest "correct" operation.

It is interesting what the stock values are supposed to be for that sensor. It might give you a clue.

 

[Heggy]

Yes and the strange thin is higher resistance should make the fan turn slower, as temp goes up and resistance goes down the fan should turn faster. Neither is happening, so there must be something else like the ac connections. Also My engine is limited to 4500 RPM. This may be a sense of an engine overheat... Or ECU is dead....

 

[Heggy]

Hooked up the AC clutch relay and 2 feeds to the ECU for AC (A/C & ACMG) also tried to jumper FAN ECU pin 7 to ECU PIN 7 (thru EA2) best guess as I don't have the ECU internals to know what is what. Still no luck.....