I recently bought a 2000 Ranger with 2.5 engine. When I test drove it, I checked the AC which worked fine, but the heater never did warm up, just blew cold air. The dealer had a mechanic check it, he said all the mechanic did was pop the hood and tap something and it worked. After I got the truck, the heater did work, but since then has not worked every time I've tried it. It either works fine, or just blows cold air regardless of the hot/cold setting. The water temp gauage reads normal. I've read through some of the other threads about Ranger heater problems and a lot of them seemed to point to the blend door, but that wouldn't be under the hood, would it? Also, when I tried to read the "Blend Door Fix" from the Ranger Technical Info list, it said that thread couldn't be found. Exactly what would he have tapped on under the hood and where would it be located? Could it be something easy and cheap to fix?

I've got to say, I've already learned a lot of other things about my truck since finding this site a week or two ago. I plan on changing the plugs and wires and have learned that double platinum are best, and that the driver's side plug wires are going to be a real pain. I did replace the air filter with a Fram filter and read some more posts that maybe Fram ain't so good, even though I've used them for years without any problems. Had to be better than what I took out, you almost couldn't see the filter for the amount of dirt caked on it, and even found a dead dried-up mouse in the filter box! Oil and filter (Fram again) have already been changed right after I got it.

Thanks in advance for any help!!

 

My understanding of the "Blend Door" is that it adjusts the temperature of the air coming into the passenger compartment. One extreme is all cooling, the other is all heating. Now most people have a middle point that they like. So the door gets used to being in that position. Dirt builds up around the door and "locks" it in place. When the door is now asked to be in someother location it might be stuck in the old location until it is bumped, tapped, encouraged by a supplemental force to the new location.

My understanding is that the blend door is located in the cab under the instrument panel. The location should be connected by duct work to both the heater core and the AC core. The bend door is located inside the duct work. There should be a metal shaft that the door pivots on. Tapping this metal shaft, or trying to move it may correct the problem temporary.

The best solution would be to open the duct work and repair the blend door. Not too easy to fix and hence not too cheap if you don't want to do it yourself, but if you do the labor yourself I don't think it should be too expensive, especially if all the problem is a build up of dirt.

 

Check the heater hoses, they should both be very hot. If they are then I agree with g_k50 that the prooblem is the blend door.

 

My '97 4.0 has a Temp control valve that is vaccum operated. Believe when switch moved to HEAT vaccum applied to valve which
opens and permits hot water to flow to heater core. That is why the mechanic raised the hood--unstick the valve.

 

I had checked and both my heater hoses are definitely hot. I was looking around on one of the auto parts websites and they list a heater control valve for about $20 bucks for my truck, and there are a couple different types, maybe this is that control valve under the hood? When I looked under the hood to see where it might be, there are a couple possibilities that the heater hoses run to, one is near the front of the motor near the thermostat, and the other is back along side the passengers side of the motor.

 

Pic of heater control valve:

 

Great picture, much better than any in my haynes manual. Got the part at napa yesterday and installed, hopefully this was my problem, because it was a cheap and easy fix. I'll try the heater every now and then to see if it works all the time. Thanks for everyone's help!