Heater core bypass found in newly bought ranger

[Curious Hound]

My 97 F150 has good cold A/C on the original compressor.

Personally, for things that affect safety and reliability, I go with the "replace it at safe intervals" theory. But mere creature comfort luxury items, I wait til it breaks or shows positive signs of immediate impending doom. Just me being cheap, I guess.

 

[Blmpkn]

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This is just one result of many on Google including forum posts by many who have only had a decade or so of luck with a single compressor.

I never claimed to be an hvac pro, that shits all witchcraft to me honestly.. boiling things to make cold air.. witchcraft.

 

[racsan]

I had a ‘97 ranger with working a/c, even after it had been rolled, had 180,000+ miles on it, was going to save the compressor for “on board air” on the ‘94 but decided not to. Dad bought a 77 F250 in the early ‘90’s a/c worked great on it (and was R12 at that) Ive seen compressor clutches go bad but only a couple of compressors themselves die.

 

[Camjacobsen]

No, the Grey vacuum Line is not why AC is not working, and yes it goes to the heater by-passes vacuum valve, its not cut, the hard plastic lines just get brittle and break like that
You can use rubber hose to splice it back together

The heater by-pass valve is only used in MAX AC setting to stop hot coolant from flowing thru the heater core in the cab, this can reduce temp in cab by a few degrees, ain't much but ain't nothing either, lol

MAX AC setting also closes the Outside Vent, so cab air is recirculated, this is the main benefit of MAX AC since you are re-cooling already cooled air vs trying to cool 90+deg air from the outside
MAX AC is also good to use off-road because it won't pull in DUST via outside vent

AC doesn't have a high or low setting, just on or off, so regular AC cools outside air coming in, MAX AC cools recirculated air


As for AC being shot, 99% of the time its because there was a leak in the system and pressure is now too low for the compressor to activate safely
Most AC fluid has a dye in it that will show up at a leak point, but not all
The condenser, in front of radiator, is the most common leak point

An AC service tech can test if your system can hold pressure and if not, what is leaking, and give you a list of parts that need to be replaced, you can do that labor and then bring it back to be flushed, filled and checked
This is by far the least expensive option as you can waste alot of time and money on fluid and un-needed parts
And you can ruin new parts if installed in an unflushed system

Hey Ron,
I believe the grey line was cut becau

No, the Grey vacuum Line is not why AC is not working, and yes it goes to the heater by-passes vacuum valve, its not cut, the hard plastic lines just get brittle and break like that
You can use rubber hose to splice it back together

The heater by-pass valve is only used in MAX AC setting to stop hot coolant from flowing thru the heater core in the cab, this can reduce temp in cab by a few degrees, ain't much but ain't nothing either, lol

MAX AC setting also closes the Outside Vent, so cab air is recirculated, this is the main benefit of MAX AC since you are re-cooling already cooled air vs trying to cool 90+deg air from the outside
MAX AC is also good to use off-road because it won't pull in DUST via outside vent

AC doesn't have a high or low setting, just on or off, so regular AC cools outside air coming in, MAX AC cools recirculated air


As for AC being shot, 99% of the time its because there was a leak in the system and pressure is now too low for the compressor to activate safely
Most AC fluid has a dye in it that will show up at a leak point, but not all
The condenser, in front of radiator, is the most common leak point

An AC service tech can test if your system can hold pressure and if not, what is leaking, and give you a list of parts that need to be replaced, you can do that labor and then bring it back to be flushed, filled and checked
This is by far the least expensive option as you can waste alot of time and money on fluid and un-needed parts
And you can ruin new parts if installed in an unflushed system

Hey Ron,
The reason I believe it is cut because the entire heater hose is missing from the engine bay. The coolant lines that come from the firewall have nothing attached. I haven't been able to locate where the hose comes out of the engine to be able to see if someone just blocked it off or rerouted it. I live in area where the heater should never come on year round. Will not having that vacuum line connecting to the none existent heater control valve affect the MAX AC?

You're definitely right about there being a leak because I recharged the AC system when I first bought the truck figuring that it would either fix the problem or all leak out. To no surprise a week later, I no longer had AC. The previous owner replaced the radiator at 90k or so. Do you think the mechanics who replaced the radiator would have seen the "leaky" condenser?

Appreciate the advice,
Cameron

 

[Camjacobsen]

The A/C compressor is still a working original in my:
02 Ranger
94 Mustang
79 F350... still R12.

Care to update those numbers a little.

I live in a very warm climate year round where the AC is always turned on. I believe this is very situational and depends on how much the AC system is ran.

 

[Camjacobsen]

I'm not positive on the valve, BUT if your compressor is shot.. you probably need to replace the whole system to have AC back and working for more than a week.

A compressor should be a maintenance item after 8 years or so, cause if a compressor gives up the ghost it more or less takes the rest of the system with it.

Well the AC system is not working in the truck currently. I recharged the system and it went out about a week later. Theres a leak but unsure if the grey vacuum line that runs from the non-existent heater control valve is contributing to that problem.

 

[Camjacobsen]

I wouldn't replace a compressor as maintenance. A qualified shop should be able to flush most of the components if a compressor fails, the accumulator and orifice tube most likely will need to be replaced. Just blowing freon into a leaking system often causes problems, the system should be evacuated and the charge should include oil. Those charge-it-yourself kits blow air into the system because the hose is full of it and seldom have compressor oil in them. I don't think I've ever seen a leaky Ranger heater core but I've seen many leaky shut off valves dripping coolant at the right rear of the engine compartment. Step one is to find out where that vacuum hose goes, if the blend door isn't moving you may not get cooling or heat.

That grey vacuum line runs straight to the back of the climate control in the cab of the truck from the research i've don

 

[Camjacobsen]

I'm sorry, that makes no sense to me whatsoever. If the compressor has a problem, then sure - replace it as needed. But it's definitely not a maintenance item to replace ahead of time.

This wouldnt be something

Wait...

You're going from 'stopped blowing cold' straight to 'the compressor died'?

I bought the truck with the ac not working..

 

[RonD]

Just cap the end of the grey line
Yes, with that open(leaking) in MAX AC there may not be enough vacuum to hold the fresh air vent closed

The engine would randomly over heat if the hoses were just blocked, the heater core hoses are the water pump by-pass
So there needs to be flow from the upper heater hose on intake back to water pump heater hose
Either thru the heater core or just via a looped hose

You added refrigerant to the AC system, did it have dye in it?

 

[Craig0320]

There seems to be little to no effort of diagnosing actual problems and just throwing parts at something. Rond gave you great info on all the questions you asked early on. You keep asking the same questions . Using your logic of replacing the compressor because it's time even though most likely you could dye the system and find a leak in a low pressure valve or something as simple that then why not replace an engine, transmission, or rear end when it develops an oil leak. My 300,000 mile 98 2.5 5 speed had the original compressor on it when it was sold. An a/c system will last a very long time with proper refrigerant and oil capacities in the system. Take the time to learn the system's before assuming anything.

 

[Camjacobsen]

No, the Grey vacuum Line is not why AC is not working, and yes it goes to the heater by-passes vacuum valve, its not cut, the hard plastic lines just get brittle and break like that
You can use rubber hose to splice it back together

The heater by-pass valve is only used in MAX AC setting to stop hot coolant from flowing thru the heater core in the cab, this can reduce temp in cab by a few degrees, ain't much but ain't nothing either, lol

MAX AC setting also closes the Outside Vent, so cab air is recirculated, this is the main benefit of MAX AC since you are re-cooling already cooled air vs trying to cool 90+deg air from the outside
MAX AC is also good to use off-road because it won't pull in DUST via outside vent

AC doesn't have a high or low setting, just on or off, so regular AC cools outside air coming in, MAX AC cools recirculated air


As for AC being shot, 99% of the time its because there was a leak in the system and pressure is now too low for the compressor to activate safely
Most AC fluid has a dye in it that will show up at a leak point, but not all
The condenser, in front of radiator, is the most common leak point

An AC service tech can test if your system can hold pressure and if not, what is leaking, and give you a list of parts that need to be replaced, you can do that labor and then bring it back to be flushed, filled and checked
This is by far the least expensive option as you can waste alot of time and money on fluid and un-needed parts
And you can ruin new parts if installed in an unflushed system

Hey Ron,

Coming back to this a month or so later. I think my post was sort of misinterpreted this wasn't mainly meant to be a question about my ac. I was aiming at how there is no existing heater hose or heater control valve.

The line that runs to the heater control valve was not brittle and broke but was snipped after the heater hose and valve was removed and bypassed.

Due to this line being cut I think it could be contributing to my vents producing lower than normal air flow and of course an associated problem with my MAX AC.

Would it be worth going out of my way to test my heater core for leaks before replacing the heater control valve, grey vacuum line, and hoses? Correct me if i'm wrong but It seems as though you would only want to remove the heater hose, valve, etc. if there was a leak somewhere internally?

 

[RonD]

There is no "heat control valve" its a Heater Core by-pass valve, its an on/off valve no Temp control
The engine bay valve either circulates coolant thru the heater core in the cab or by-passes the heater core and sends coolant back to water pump, so on or off
A leak in a heater core will cause wet carpet on passenger side and a musty/coolant smell in the cab

Temp control in 1995-2011 Rangers is done with an electric motor in the cab, the Blend Door Actuator
Air flow strength is from the blower/fan speed
Air flow direction, defrost, panel, floor, is set by vacuum "motors" that open and close vent doors in the cab
None of these would be effected by having, or not having, the by-pass valve installed and working

In summer months its not uncommon to get less and less air flow from the fan because AC's Evaporator is TOO COLD, its freezing moisture in the air on its surfaces which blocks air passing thru it
Blower/fan>>>>>Evaporator>>>>>>>>>Cab>>>>>Vents
All the air from the fan must pass thru the Evaporator before it can flow into the cab and then to the vents

The Evaporator "Dries the air" going into the cab, moisture in the air condenses on the colder evaporator fins/passages it then drips off onto a tray under the evaporator which has a drain hose in the firewall, and the water will drip out onto the ground, you see that on all vehicles with AC, water dripping out on warm days
And if AC Evaporator's surfaces are below 32degF then that water can Freeze in the Evaporator and block air passage

(Freezers run with temps well below 32degF to freeze foods, but they also have a heater circuit to prevent icing, automotive AC has no such heater)

AC systems that are low on fluid often run too cold on Hot days, this has to do with higher pressure in an AC system when outside temps exceed 90deg
And this type of blockage would be more common in humid and hot areas
Just check AC lines at evaporator(under the hood) to see if ice is forming on the outside, if so then evaporator, inside the box, has even more ice forming, blocking air flow thru it

The grey Vacuum hose for the by-pass valve only has vacuum present when selector in cab is in AC MAX or OFF
If Grey line is unhooked and not "Capped", then in OFF position there would be vacuum loss but it would not effect anything and its not a "vacuum leak" that could effect engine
In MAX AC setting the uncapped Grey hose could effect vent controls, defrost, panel, floor, but vacuum at the control panel would already have to be marginal, i.e. a crack or leak in vacuum reservoir or hose from it to cab
If your air flow from the fan changes to Defrost Vents when accelerating, that means you have a vacuum leak in the reservoir or in the hose from reservoir to cab

 

[dirtymike]

Thanks RonD, I was taking notes. Dirty