Heater problems

[JOHNCROFTON]

I have a 94 Ranger (4cyl. 5spd) and I get no heat. New water pump, radiator full, new radiator hoses, controls all working normally (switching air to floor to defrost) but no heat. A/C works great. Where do I start looking??

 

[Alan_nc]

Are both of the heater core hoses connected? When the engine has warmed up do both of the hoses get hot? If one is hot and not the other you may have a plugged heater core.

The good news is: If you have to replace the heater core this has got to be the easiest one in the world.

 

[scotts90ranger]

Yeah, I would look at the heater core first. Unless it has a valve that isn't connected in one of the hoses (I think if they have A/C there's a valve) it's probably plugged, and what Alan said is true, it's 2 hose clamps and 5 screws to change the heater core in '83 to '94 Rangers... I wish it was that easy on my '97...

 

[RonD]

I would bet heater core is clogged up

But first do this, warm up engine and then feel both heater hoses at the firewall, BOTH should be hot, you don't have to have heater on, there should always be flow thru the heater core
If one is much cooler than the other then NO FLOW, so you will need to change heater core, its easy on a 1994
If you have noticed the dash temp gauge going up a down a little for no reason, that means heater core is clogging up

If both hoses are HOT then problem is the Blend Door, which is CABLE operated in 1994
The Climate control has a SLIDER for temp control, this slides a cable that opens and closes the blend door
The Blend door covers the Heater core in the cab, when slider is at HOT then all air from the Fan is sent thru heater core
When slider is at COLD then No Air passes thru the heater core, its routed around it

You can see the cable above glove box, if you fold down the glove box, looks like a bicycle brake cable, and you can see it move the blend door's arm if you move the slider

Heater core is easy to swap
Put a towel down in passenger cab floor
There are 4 screws that hold a bottom plate on to the heater box
One is up high just behind glove box
one is just above the transmission hump near firewall so need a short socket
other two are in the other 2 corners, easier to see

Cover just pulls down

Remove the 2 hose clamps in engine bay, and remove hoses
You need to pull back and tilt the core to lower it down in the cab, and thats why towel is there, lol, coolant WILL spill out
Take core out and empty it, you will be amazed on how heavy it is compared to new core, that how clogged up it is

You can keep ANY heater core cleaner, on any vehicle, by swapping heater hose around at firewall, to reverse flow thru the core, do this every 2 years, when you change the coolant

 

[JOHNCROFTON]

Neither heater hose is near as warm as radiator hose.

 

[RonD]

Clogged heater core

 

[black_demon69]

I have always just clamped off both hoses to heater core then removed hoses from heater core and blew some air through the heater core (just enough pressure to force coolant out so it doesn't leak inside) then replace heater core and reattach hoses remove clamps and top off cooling system.. this is the no inside mess way of doing it

as a side note I have also added 2 flushing tees to heater core lines and have been able in some cases unclogg them

 

[JOHNCROFTON]

It was a stopped up core. R & R took about 15 minutes. Thanks for the info

 

[rosscob]

I'm having the same issue with my '88 XLT 2.3. I had to change the water pump and thermostat right after I bought it back in October and it seemed to work then but nothing now, just cold air. I've flushed the heater core and both hoses going to it are hot. Mine is old enough so there's no bypass valve and when you move the temperature control you can hear the blend door opening and closing. What else could it be? I drive about 5 miles to work every day and by the time I get there the temp gauge is well past 1/2. I'm stumped.

 

[RonD]

Heater core is blocked, it will still pass coolant at the top so hoses heat up

The heater core is not hard to remove, even just to check it, in 1983 thru 1994
New core runs $35-$45

Article here: https://www.therangerstation.com/tech/heater-core-replacement-1983-1992-ford-ranger/

Lay a towel down in the cab, for sure

When you get the core out flip it over to drain the coolant, after coolant is drained out it should be light as a feather, clogged core won't drain, it will be heavy

You should swap heater hoses around every 2 years or so to reverse the flow thru the core, it will help keep it cleaner

Anytime you need to refill, remove 1 heater hose from the core and then top up radiator, this allows air in the engine to escape from behind the closed thermostat
When coolant starts to come out the open core port and its hose put the hose back on, all the air is out, no burping required

 

[rosscob]

Both hoses are hot to the touch. I just got back from a 50 mile trip and still no heat in the cab.

 

[black_demon69]

Both hoses are hot to the touch. I just got back from a 50 mile trip and still no heat in the cab.

Have you checked the headgasket or the tstat is the tstat stuck open?

 

[RonD]

Both hoses are hot to the touch. I just got back from a 50 mile trip and still no heat in the cab.

Which means NO HEAT is being lost passing thru the Heater core, so its clogged

One hose should be cooler than the other, and if blower was on HIGH and Temp set to HOT then much cooler
Right now coolant is just passing thru the upper area between the 2 pipes, core stays cold at the bottom

 

[rosscob]

Have you checked the headgasket or the tstat is the tstat stuck open?

New thermostat, no head gasket issues. I thought if the heater core was clogged, one hose would be cold due to no hot water passing through it. I flushed the heater core a couple weeks ago, both ways, and it seemed to pass water with no issues, both ways.

 

[RonD]

Yes, but passes the water thru only the top tubes

If engine is warmed up and fan is on high one hose should get cooler that the other, if they both stay hot then there is no heat transfer going on in the core as air passes thru it
Assuming blend door is working then core is clogged up