Hello all! New here to the forum so try to take it easy on me. Looks to be a lot of helpful folks here though, so here we go!

A few months back we bought my grandpa a 1994 Ford Ranger as the 88 Nissan that I gave him was almost gone due to rust. Ever since buying the truck I noticed that it was running pretty cool. The temperature gauge starts below the "C" and after the truck is as heated up as it gets, it is resting on the "C". It never gets any hotter than that. The Picture at the bottom of the post is the truck at "normal operating temperature".

About a month ago I replaced the thermostat thinking that was the issue with running cool. Even after a nice new thermostat, it's running at the same cool temperature.

Now that winter is here, my grandpa has been saying that the heater seems to be hit and miss. One morning he gets in and will have heat and the next he won't. All last week actually he never had heat. Yesterday I flushed the heater core and some nasty stuff came up but nothing too awful and nothing in any great amount. After doing that, I ran the truck and noticed that I had just a bit of heat but when revving it or while driving it, I had good warm heat.

Are these two issues related? If not, what should I be looking at next?

Thanks all!

1994 Ford Ranger
2.3L l4
5 Speed manual
120k miles

Ok first your gonna wanna rule out the very common issue of just having a crap temperature sending unit giving you false readings. Remove the sending unit and hook up a multi meter to it on ohm setting. Attach the ground to the body of the sender and positive to the terminal. See what it reads cold, then dip it in a pot of boiling water and see if that number changes. (The exact numbers aren't that important, mainly because I don't know them off hand lol) But if it doesnt change much or at all you need a new sending unit and the heater is a separate issue. If it works, re install it and test it again with the multimeter while on the truck after its "warm" wait 15 minutes or so with it idling. If the readings are the same as during your boiling pot test, your gauge or wiring is broke. If it now reads cold on the multimeter you know it's an actual problem with the engine not warming up.

Is the sending unit what is located on the back/side of the engine for these trucks? Have been looking up videos and that's the only place I am seeing.

Yes should be on the rear drivers side of the block on the 2.3 if i remember correctly. Will have a single wire connection. If it has 2 wires that is the "SENSOR" not the "SENDER". Two different things. You want to test the "SENDER".

The temp sender is on the drivers side of the block, above and to the right of the oil filter.

If you have the ignition ON, and ground the sender wire, the gauge should peg immediately if not sooner. I would not leave the wire grounded for more than a second as it seems it is more juice/volts than the gauge should be getting normally.
I would start the engine, cold, and put my paw on the upper radiator hose. It should start out cold(ambient) and then stay cold, and then get hot. It should not 'gradually warm up' and if it does, then the thermostat is either broken or installed without sealing properly. The stat has to be crammed into the housing so the rubber gasket is seated against the shoulder inside the housing, then bend the 'legs' to hold it in place. Or, bend the legs outward a bit so it is a 'cram fit' into the housing, and push the stat in place. The flat feed on the legs should fit into the machined groove around the base of the housing, to hold the stat in place.
If the hose stays cool, and you have no heat, then likely the heater core is blocked.
If the engine finally gets hot(see above, where the upper hose is hot), the hoses to the heater core should BOTH be too hot to leave a hand on for more than a short while. I emphasize that both should be hot as if one only is hot, all the flow through the heater has transferred all the heat it has, and is returning cool coolant. There should be enough flow to keep both hot... If not, either air in the heater core, or more likely, a plugged heater core. You may be able to attach a hose and flush the heater core of the muck, but you may have to replace it. If you flush, try to reverse the flow from the garden hose opposite to normal flow from the water pump. Choose the hose that is not connected to the water pump to stuff flush water through.
If you have air bubbles, the heater will be intermittent. You may be able to burp them out by maneuvering the hoses to let the air get to the highest spot, and then allowing coolant to leak out along with the air. I have a flushing tee installed that I can use to burp the heater core by loosening the cap.
tom

Thanks! I didn't test the gauge yet but did try some other stuff just a couple of days ago.

I parked the front of the truck on some ramps and then let it cool. After cooled I popped off the radiator cap topped off the radiator (didn't take much at all) I then started the truck with the cap off and let it idle while occasionally revving it. After a couple of minutes I got out and felt the top hose and it was cool. However, when wrapping my hand around the top hose (and maybe I was imagining things or it was engine heat) the very bottom of the hose felt a little warm. Not much, but a little. After a few more minutes of idling/revving I felt the top hose and it was good and hot. There was not a "gradual" warm up.

At that point, I turned the heat on max and felt what seemed like lukewarm air. I went to the front of the truck and jiggled both the hoses to the heater core quite a bit. I got back in and revved it quite a bit at decent high RPM's to try to force out any air pockets. After doing this a few times I noticed that the temp gauge did actually get higher than normal. It didn't get near the middle of the gauge but was definitely higher than the picture I first posted.

After all of that I took the truck for a spin first with the heat on and then off. With the heat on max I was getting a little too warm in the truck.

At this point my grandpa has the truck again and I told him to let me know how it does since he said the heat was cutting in and out. I am waiting now to see what he says. It sounds like maybe the problem isn't totally fixed but may be quite a bit better?