teamafx

iTrader: (4)

I have sensor on the side of my waterpump housing, but it only has one wire. Can someone snap a photo of their coolant temp sensor and the connector (with wire colors for engine harness)?

wstrohm

The manual (page Z-32) calls out a green wire with white stripe for the sensor connection to terminal 3E of the PCME, and a brown wire with black stripe for the common (return) wire. In the picture, the green sensor is the two-wire coolant temperature sensor.

The black sensor is the "water thermoswitch" which has only one wire, black with a red stripe. That is shown schematically on page Z-40 of the manual and controls coolant fan relay No. 3. Its return is chassis ground through its mounting screw threads.

VTECthis

iTrader: (4)

While on the subject, I installed an FC thermoswitch, and saw no change in the temp when the fans come on. I have also replaced all fan relays. So my question is, could an old temperature sensor be reading low from age, and not send the proper temp to the ecu, causing the thermosensor to trip the fans at a higher temperature. Hope this makes sense. Im wondering whether the temp sensor can affect the thermosensor in any way, basically. My fans still arent coming on until 225 degrees F or so, of course assuming that my temp gauge is reading correctly.

wstrohm

@VTECthis,

If you look at the (main, upper) Coolant Fan Control Table (attached), in the column titled "Cooling fan relay No.3," you will see that as you look down the chart, "Off" changes to "On" in the row titled "Engine Coolant Temperature above 108 and below 117 degrees C (226-243F)". Since the Water Thermoswitch controls ONLY the #3 relay, changing from an FD to an FC Water Thermoswitch ONLY does the following:
1) Changes "Off" to "On" in the two rows just above the original row for both the "Engine coolant switch" column and the "Cooling fan relay No. 3" column.
2) As the result, it also changes "Low" and "Middle" in the upper two rows under "Cooling fan operation speed" to "Middle" and "High" respectively. (This is explained by looking at the fan schematic in the Workshop Manual, also attached.)

The upshot of that change is that with the FD switch, for temps between 226°F and 243°F the fans would run at either low or middle speed (depending on A/C off or on). But with the FC thermostat installed and temps the same, the fans will run at middle or high speed (depending on A/C off or on).

So the temps turning on the fans are the same, but the fan speeds are higher with the change to the FC switch, for more heat transfer.

rousu

What are likely causes if the cooling fan always is running even when the car is cold and the engine not running?

Could that happen because the temperature sensor is not working or not connected right?

Ceylon

iTrader: (3)

Don't have your AC on by any chance, do you? If not, it's a wiring/sensor fault.

Regarding the OPs question, it will be either the thermosensor, coolant level sensor or an aftermarket sensor that you're looking at, post a pic and we can tell you what it is.

wstrohm

It's also possible that you have the fan recall circuitry in your car. If you do, there is a timer circuit that controls how long after the engine is turned off that the fan will continue running. (It's supposed to run for 10 minutes.) If that circuit has a problem, it is possible that the fan just won't turn off at all. A schematic of the modified circuit is attached below. The new unit is the "Cooling Fan Control Module" at the right of the schematic.

rousu

Thanks.
1. Air conditioner is off
2. Will take a close look at the timer. And all the fun of finding the real wires and real boxes that in the car that correspond to the diagrams...
3. There may be a problem with wiring; looks like some of the connectors to wires were the cheap type that pushes pins in through the insulation, instead of stripping the wires and clamping, or stripping and soldering. A wire wiggle at the computer started and stopped the fan.
As uncle Al used to say: It is designed to work, so just fix it and it will work. .... soon ...

wstrohm

The fan control box is located near the PCME (ECU) behind the right-side lower front cabin "wall." it's fairly small. No picture, sorry.

rousu

Probable answer to the problem:
The mechanic says there are two plugs into the computer that are both black plug color that have the same configuration of pins; and the wrong cables got plugged into the wrong places. Swapping them into the correct places appears to have solved the problem of the fan running continuously. Says one of the plugs is for cooling wiring, not sure what the other one is yet. I do not know if compatible plugs of the same color is a design feature or a result of a repair somewhere along the line, but not a good feature to have same color nor to have compatible plugs. A couple more little problems and the rebuilt engine will be powering down the road again.

wstrohm

When I still had the fan recall circuitry in place, I had trouble keeping the battery well-charged. The fans use a lot of current, and if the car in't run a lot, the discharge due to the fans running after the engine is off can catch up with the charging from the alternator. Eventually I removed all the fan recall stuff and just swapped the coolant fan thermoswitch with one from an FC. Not sure that running the fans with the engine off does much good anyway. Cools the radiator, but since the water pump is not moving water, it doesn't do much for the engine itself.