I substituted a 04 thermostat without the heater, instead of the stock thermostat with the heater, in my 02 ranger 2.3.. I added a resistor to bypass the thermostat heater so the computer thinks there is a heater in the thermostat. It doesn't open. The lower rad hose is cold.
It is a 195 degree stat. The one with the heater and the one with out looks the same as far as bolting up. Any Thoughts?

Thanks.

my guess is you have air trapped in the cooling system, the 2.3 can be very hard to purge all the air.

with the engine cold and off and the pressure cap off the expansion tank and the tank at the full mark squeeze the lower hose until you do not see air flowing into the tank.

make sure to keep the coolant at the max line so you do not suck air back into the engine and pump the hose slowly to avoid sucking air back into the engine.

while squeezing the lower and upper radiator hoses one at a time the fluid level should increase slightly then go back down.

the thermostat you installed may not have a jiggle pin or other vent built into the thermostat which will not allow the air to escape from the block'

If this is the case I suggest removing the aftermarket t-stat and install a quality part that has a built in vent.

For now do your best to purge the air if any is present in the system while the engine is off.

if your successful you should see the coolant level drop to the point where you will need to top off the tank frequently once you are sure the radiator and block are full or nearly full start the truck and turn the heater on.

Keep pumping the upper or lower hose whichever hose you can reach safely without getting your hands caught up in the serpentine belt.

while pumping keep an eye out for air bubbles if you get any air keep pumping. if you no longer see any air just make sure the expansion tank is topped off with coolant then put the cap back on and let it warm up and feel the lower hose again to make sure the t-stat is opening properly.

I went through all of this and yet for nearly a week I had to keep topping off the cooling system each morning until finally I had my trucks cooling system air free.

others on this site may have a better way of purging the system of air so keep checking back.

I do not know for sure air in the system is causing your problem yet this is where I would start.

if this does not help the only suggestion I would have is replacing the t-stat with a quality part that has the jiggle pin

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2002 Ford Ranger 2 Dr Standard cab 2.3 5 SPD 7.5 373 gears

How do you wire in the resistor?

I've put a 180F mechanical thermostat into my '03, and of course the Check Engine light's now on. I need to put in a resistor, but I don't know exactly how.

Thanks

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I was going to one day install a mechanical only T-stat yet after reading
this I decided against it.

Hi here is some information I found on our over engineered thermostat from Alldata Diy in case you did not know.

The primary objective for the thermostat heater control is for improvement in the economy and thermal efficiency. The system consists of a high temperature (98°C/208°F in lieu of a 90°C/194°F ) thermostat (Figure 50) that has a resistive heater within the wax element. The heater is controlled by the PCM dependent on engine speed, throttle position, engine load, vehicle speed, air charge temperature, transmission oil temperature and engine coolant temperature.

During low speed, low load and low air charge temperature conditions, the thermostat heater is OFF and the engine is allowed to operate at an elevated coolant temperature. This should result in lower internal friction and higher thermal efficiency, both leading to improved fuel economy.

During high speed, high load, high temperature conditions (air charge, transmission oil or engine coolant), the PCM output is energized with a duty cycle to the thermostat heater. This heats the wax and forces the thermostat to rapidly open wider allowing extra coolant to flow from the radiator. This will reduce the coolant temperature and improve with performance demand.

It should be noted that the heater is only capable of supplying a SMALL amount of additional heat to the wax element; it is NOT capable of opening the thermostat alone. The thermostat is 100% duty cycle for short calibrated time and than the duty cycle is reduce to a maximum of 70% on and 30% off.

Approximately, unheated, the thermostat will begin to open at a coolant temperature of 98°C (208°F) and will be fully open at 115°C (239°F) . Energizing the heater will reduce the opening temperature to about 80°C (176°F) and the fully open temperature to 110°C (230°F) .

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2002 Ford Ranger 2 Dr Standard cab 2.3 5 SPD 7.5 373 gears

Ea... Read up some more on the 'electronically assisted' stat. I think if you do, you'll find that it goes a little to close to the 'overheat' condition. The 208F does not allow much room for maintaining usable power before getting too hot, and then the timing, etc are diddled with, reducing engine output. In short, it may get too hot too quick, not be able to recover to 'good' temperature, and cut back on power the engine can produce.
I base this on readings here and maybe at therangerstation.com ...
tom

Changing to a mechanical thermostat was a great decision for me. Before that, my temp gauge needle would sometimes creep up slightly on a hot day while idling at a stoplight w/ AC on. I thought maybe it was because my aux fan wasn't functioning properly. But after switching to mechanical t-stat, my temp needle stays stock still where it's supposed to. So far I'm very pleased with it.

And to OP (or anyone else in the know), could you explain how to wire in a resistor for the two-wire connector that's just hanging loose in there & causing the CEL to stay on. I'd love to do this... Thanks!

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All I can say is my 2002 with 141K on it and a stock style t-stat never goes above 1/2 on my temperature gauge, with the AC on and idling for hours.

What temperature it is actually running at I have not checked with my scan tool.

I will say when I first got my truck the temperature would creep up like you mention but that was from a worn fan clutch and sand loaded up in the fins of the condenser and radiator.

The previous owner used to go off road with this truck and I guess liked to play in the mud yet never flushed out the condenser and radiator fins.

I would consider swapping out to a mechanical only if the heated one only opened electronically however that clearly is not the case.

As far as how to install a resistor that should be easy however using the correct resistor could be another problem altogether.

There just is not enough intelligent information out there for me to make the swap to a mechanical only.

I may be wrong but what I would do if I made the swap is measure the heater circuit in the old t-stat housing using a ohm meter then I would measure the supply voltage to the t-stat lets say for arguments sake it is 12 volt 30 ohm resistor based on measurement you have taken.

then you would just need to strip back some of the insulation at the two wire connector and solder in the resistor and tape it up.

I bet someone here has found out exactly what resistor is needed to keep the check engine light off, like I said installing it should be easy.

But please do not go by what I said since I have not done this mod and do not plan to.

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2002 Ford Ranger 2 Dr Standard cab 2.3 5 SPD 7.5 373 gears

Harbor,

Read this if you haven't found it already:

Duratec cooling mods -- Need to clear CEL

But any way, you just need a 1500 ohm 1/2 watt resistor from radio shack. Cut the connector off the thermostat wiring (or leave the connector on and do like Ea said above about stripping back the insulation), solder the resistor wires onto each of the wires, tape or heat shrink it up and you're done. I still haven't done mine yet because I want to make it plug-n-play should I ever decide to revert back to the stock electric thermostat.

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2003 Ranger XL | 2.3L | 2wd | 5spd manual | standard cab | short bed | 112" wheel base | 3.73 rear (open diff) | no power windows or locks but at least it's got A/C!

EAOUtlaw:

15000 ohm resistor is what others use.

Because I don't know anything about electronics, what I'm really wondering is:

1. do I wire in a resistor onto each wire respectively, keeping the plastic connector on?

OR


2. do I cut the plastic connector off and attach a resistor between the two wires, thus joining them together with just the resistor between them?

Thank you!

EDIT:
Soledad: Just saw your post, thank you!!

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Harbor,

I meant to ask you, but, do you have emissions testing where you live? I don't here but thought I'd ask.

I'm sure that 180* thermostat is probably causing the engine to run a tad richer and so I have wondered if converting from our electric thermostats to non-electric would actually cause an emissions failure.

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2003 Ranger XL | 2.3L | 2wd | 5spd manual | standard cab | short bed | 112" wheel base | 3.73 rear (open diff) | no power windows or locks but at least it's got A/C!

Soledad, thank you - I just read through that whole thread that you linked. Really interesting. So what is your situation right now with your connector? Is it just hanging & triggering CEL or do you have it plugged into the old thermostat & they're hanging under the hood?

Nope, we don't have emissions testing in FL.
I have not noticed any change in MPGs but I will know for sure if there's a change the next time I fill up the tank and do the miles/gallons math. But it's still impossible to know because if my MPGs drop it could also be attributed to recharging my AC system too, which now blows super cold.

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Yeah, I just have it plugged into the old thermostat and zip tied it all up out of the way. Once I can figure out a way of making it plug and play then I'll install the resistor I bought.

Regarding mileage, I'm getting about 26 mpg (hand calculated) in the city which seems incredibly good. I never take it on the highway so I have no idea what that would be. But I'd sure be curious as to what your fuel mileage is now with the new thermostat.

Doh! That reminds me, I need to have my A/C system looked at. Pump is cycling way to frequently making me think it's uber low on refrigerant.

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2003 Ranger XL | 2.3L | 2wd | 5spd manual | standard cab | short bed | 112" wheel base | 3.73 rear (open diff) | no power windows or locks but at least it's got A/C!

That's amazing! I know yours is manual transmission so would get better mileage - and you also use your AC a lot less than me I'm sure....but that number is just astounding to me. Did it always get that high mpg or was it a result of changes that you made to the truck?

My truck was getting 15 mpg city when I purchased it, but now gets 19 mpg city. I'm installing a new coil pack & plug wires this week to hopefully improve the chugging sound my motor makes, so that replacement might improve my mpgs even further.

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Soledad:Yeah, I just have it plugged into the old thermostat and zip tied it all up out of the way. Once I can figure out a way of making it plug and play then I'll install the resistor I bought.

You might buy an in-line fuse holder, and solder it between the two wires at a convenient spot. Take a fuse, and solder the resistor between the two ends, or if a plastic fuse(modern), across the top two connector spots. THere's a hole in the plastic for access w/o removing the fuse, use that for solder connection. You want a fuse that has blown. When you want to use the resistor, plug it into the fuse holder. When you want to go back to 'factory', remove the resistor, and install another blown fuse, and the resistor equipped thermostat. You either jumper across with the resistor, or 'open' the connection with a blown fuse.
tom

Agree. Changing to a mechanical thermostat is the best thing I ever did to have consistent power delivery. At least on my truck the electric thermostat was trash for drivability.

In my area, emissions testing is done entirely by the computer that plugs into the ECM (no tailpipe sniffer). I've had it inspected 2 times now with the mechanical thermostat and resistor mod- never had any issues passing inspection.

He has a shortbed stick shift single cab with 3.73 rear gears... pretty much the best you can get for gas mileage in a Ranger. With the truck in my sig, I get on average 22-23mpg combined. I have been been running about 90% city though lately. On the freeway or road trips, I can regularly best 30mpg no issue. If its all idling stop and go with the AC on... I can do as bad as 15mpg for a trip. There can be no doubt- these motors have to work hard to get the truck moving.

Automatic and AC with 19mpg? Sounds about right to me.

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2002 Ford Ranger XLT Supercab, 2.3L Duratec I4, 5-speed manual, 4.10 gears, ~100,000 miles
Power nothing with air conditioning; crank windows for life!
Throttle cable mod, retained accessory power mod, 2006 thermostat w/resistor mod
Headlight relay harness, Philips xtreme-vision bulbs
P235/75R15 Michelin LTX M/S2s