Thank you !

Looking at that picture, it appears that the air must first pass through the evaporator and then get routed through the heater core; is that correct ?

If so, then a blockage at the evaporator would restrict the heater core as well, right ?

A few years ago, I accessed the evaporator chamber and removed a couple wet saddle blankets and a wet dog or two from the evaporator and then meticulously covered all cowl areas and anywhere else trash could get in with screen; I did this from under the hood.

 

Okay, my brain is starting to hurt. The various bits of advice offered so far are good, but unfortunately are all over the place. We still haven't narrowed down the fault so we can fix it.

In the kindest, most gentle manner possible, I need to point out you haven't really answered our questions:

1) Is the airflow volume normal, even if not going to the correct outlet (floor, dash face, or defrost)?

2) If the overall airflow does seem low, does the fan seem to be running at normal speed? If so, the most likely culprit is crud built up on the face of evaporator. There is enough flex in the lines so the evaporator can be cleaned without discharging the refrigerant.

3) If the overall airflow volume is normal, is it going to the selected location? The actuators are vacuum operated, so run the engine and play with the bottom control lever.

• Vent and both AC positions: all air should come out the four outlets on the face of the dash.
• Defrost: all air should come out the defrost outlets
• Mix: approximately 50/50 mix between the floor and defrost outlets
• Floor: majority of air should come out the floor outlets. I think you'll still see a little (10%?) from the defrost outlets

4) Do you feel any resistance moving the upper lever? This is a cable-operated door that directs air through or around the heater core, controlling the temperature output. I think you mentioned hearing a thunk at each end of travel, so that's a positive sign.

5) Beg, borrow, or steal an infrared thermometer. With the engine fully warm, please measure the temperature of the cooling system at the thermostat housing or upper radiator hose. This value should be close to the rating of the thermostat.

6) At the firewall, please measure the temperature of the two coolant lines for the heater core. Set the upper lever all the way to the right (full hot), the lower lever to Floor, and the fan speed to high. One line (the supply side) should be nearly the same as the rest of the cooling system. The other line is the return and be approximately 30F cooler. This drop shows heat is being transferred from the coolant to the ducts. If not, you've got inadequate flow of air or coolant.

So if you would kindly answer these questions, we can hopefully steer you in the right direction for a good fix, with minimal effort and wallet damage.

 

I believe the wife has some sort of no-contact thermometer that she points at people's foreheads to tell if they are on death's doorstep; would such a device be capable of these measurements ?

 

Harbor Freight sells a $25 point and shoot thermometer gun:

https://www.harborfreight.com/121-in...ter-63985.html

Lots of other similar models out there, in various price ranges. If not calibrating a nuclear reactor, a basic model should be fine. These things are so inexpensive nowadays. No mechanic should be without one.

The medical thermometer won't work. They have a very limited range of measurement.

I wonder if your bigger and betterer fan motor is part of the equation. Even if its making lots of noise, is it actually moving the air effectively? Maybe it's mostly swirling the air around versus routing it correctly through the discharge duct in the fan housing? Is the far end of the squirrel cage close to the wall of the housing, or is there a significant gap?

Are you positive the fan is spinning in the correct direction? If spinning backwards, it will still move air outward and into the discharge duct due to centrifugal force, but the overall output will be significantly reduced.

 

Almost forgot something. Previously there was some discussion about a possible coolant leak from the heater core, but I think we can safely rule that out. Yes, leaking coolant can fog the windshield, but it certainly wouldn't be freezing in place.

All bets are off if running straight water in the cooling system.

 

The fan/blower is properly doing it's job, spinning in the right direction and plenty close to the back wall of the housing; any closer and it touches.

It has been in there a long time; and, prior to this recent situation, would blow the hat off your head through the dash ports.

Of course, I can still control speed via the four-position switch; and, I can also kick it into over-drive via the toggle-switch.

The more I think about my situation,the more I think I am going to find a big wet mess on the evaporator when I get opportunity to access it.

 

Okay ----- I have found the bear's end of my problem.

Although it was 19° this morning, by noon, it was 55°.

Block heater on since 5:30:AM(timer).

Entire radiator covered with a big custom-fit piece of heavy cardboard.

I ran an errand of about an hour, maybe longer, and left the engine run the entire time.

The gauge was at about the "O" in NORMAL; usually, with nothing covering the radiator, it hangs at the "N".

Back home and engine still running, I didn't need any scientific measuring device to tell; both heater-hoses were cool as cucumbers --- at both ends, near the engine and at the heater-core.

Holding my fingers on the 3-inch or so pipe-nipple that the ball-cut-off valve screws onto --- it's like this = 3-inch 1/2-inch pipe nipple screwed into the head/ pipe elbow/3-inch pipe nipple and then ball-cut-off valve --- I was touching the nipple that the valve screws onto; I could not reach the one that screws into the head --- the pipe was hot, but not so hot as to be uncomfortable.

The hose immediately the other side of the valve was cold as a well-digger's refrigerator.

So, obviously, I have zero circulation through the heater-core.

I guess the plan now is to drain off the coolant low enough to remove the hoses and see if I can back-flush the core --- ; and, poke something flexible back through the valve to make sure the problem isn't there.

With the A/C clutch dis-connected from power, and all the ice melted off the evaporator, I have PLENTY of air movement.; whereas, I had hardly any when the evaporator was icing over.

I recently drove a 379 Peterbilt in South Texas heat that the evaporator would ice over so bad as to start hitting the blower = turn OFF the A/C and give it a few minutes to thaw out and good to go again for a few miles.

 

As my heater hoses have a bit of age on them anyway and the outlet hose connects way down there in nearly inaccessible territory, I have been considering my options for removing the hoses to perform my investigations and back-flushing.

I have plenty of metal(brass I think) male/female 5/8" water-hose connectors; the kind that uses plain old hose clamps.

I am considering cutting the hoses at about the halfway point and installing these water-hose connectors; female on the inlet/outlet side/ends such that a water hose can be screwed on either side for easy leak-free flushing purposes.

I can attach the water hose in the back-flush direction and then swap to the forward direction to see the results.

Having such an easy means, I might be more likely to flush things out at the beginning of winter when I open the valve and not have this problem I am experiencing again.

I also intend to put together a male air-hose coupling slash male water-hose adapter so I can blow out all the mineral-laden well water once I get done flushing.

On further thinking, another thought is to install a cut-off valve in the outlet line as well; and, thus, so equipped, I can close the valves when I do my flushing and not have to drain down the radiator; this would also apply should I ever need to replace the heater core.

I have now convinced myself of all the many advantages of this plan of action and intend to employ it tomorrow, providing I have another cut-off valve and providing it isn't raining.

Once I get all this rigged up and in action, it would be a simple matter to incorporate a coolant filter as well and service would be simple.

 

Any progress?

Curious what you found with the lack of hot coolant reaching the heater core. Was it the shut-off valve causing the problem?

For the ice accumulation blocking airflow through the evaporator, there are two main possibilities:

Low refrigerant charge. This is fairly common, with a slow leak over a long period of time. You can do a full vacuum and refill so you know exactly how much refrigerant is in the system. Or you could try adding a third of a can and see if that helps. Not quite as precise, but it works about 80% of the time for me.

Misadjusted cycling switch on the accumulator. Pull off the plug to access the adjustment screw. On the switch, turn the little adjuster 1/8 of a turn clockwise to raise the low temperature limit by 2 degrees. See if that helps. If not, you can go a little bit more. Don't go hog wild, because low refrigerant can cause similar symptoms.

Whichever problem is causing the icing, it shouldn't be that bad, even in cool weather. It's normal to have a little ice collect in the corners of the evaporator, but there shouldn't be so much as to restrict airflow.

 

FWIW, here's my temp gauge after a few miles of driving to go get milk. It's about 2 miles up hill to where I get milk, and I took the long way home, about 3 miles. Outside air temp is 51F.

 

I got my window of opportunity yesterday and back-flushed the heater core.

First, attempting to flush through in the direction of travel (inlet hose), it was like a solid wall with nary a drop getting past.

Switching directions, after several quick blasts, I got a trickle and then more and then a gusher.

I kept switching directions numerous times and was getting crystal-clear water and plenty of it.

Just to be sure, I ran a flexible plastic wire-puller back through the existing valve, plumb into the head.

Once I got the blockage flushed out, I swapped the hose-barb that was in the existing valve for a male water-hose adapter.

On the outlet hose that previously had no valve, I added an identical valve with male water-hose adapter.

I installed female water-hose connectors in the ends of both heater hoses such that I can unscrew them instead of having to fight them loose from hose-barbs.

Now being equipped with two valves, I can shut off both valves to service/flush the heater core and hoses without having to crawl underneath and drain down the radiator and then have to vent the system when putting the coolant back in.

Without it being such a dreaded headache, I will be more apt to regularly back-flush the core.

The barbs on the female water-hose connectors were plenty long enough that I used double clamps.

Once I got all hoses connected and the radiator filled, it was dark as Miller's Cave and I called it a night.

Within minutes, it was pouring the cold rain and it hasn't stopped since.

I have not yet had opportunity to run the engine and check for leaks and then zip-tie everything back in place.

Whether it was an issue or not, I did re-route the heater hoses underneath that A/C line instead of over the top of it; before, to my eyeball, it appeared the highest part of the system was where those hoses went over the top of that line and was probably cause for a big air pocket.

After I already had everything buttoned up, I got to thinking about it; and, in the future, when I access the heater hose/core system, I will pour as much coolant as I can manage into one of the open hoses to pre-fill things as much as I can.

When time, and more importantly, finances allow, my plan is to completely purge and flush the system and install all new hoses, including both bottom radiator hoses, the top hose, and both heater hoses.

The plan is to wait on installing a coolant filter until I get the system flushed and cleaned out; I have had several of everything I need to do this for quite some time --- swap meets are a wonderful source of such treasures if you have a sharp eye.

It appears that we have about four more days of rain; so, I may not know anything more until it finally quits raining.

 

That sounds like good progress.
When you replace the lower Radiator hose, remember to keep the spring inside of it, for the new hose, that will not have one.

 

Tell that to the three stupid good-year mini-split heater/A/C that I let the local electric company convince me to install; ever since brand-new, once it gets about 45° outside, ice will start building until it completely captures the big fan.

The local electric company got some sort of grant and qualified everybody around here for three of these units at no cost; I got three Pioneer brand 18,000-btu units; they really pushed them and filled the countryside with them; every home around here has them

The reason everyone around here calls them "good-year heaters" is because they are barely good for one year; of the three I have, only one still sort of works; the other two have been dead for some time.

The idea was to get us all switched over from burning wood to using electricity; one of the electric company guys told me "don't take down your stove" and I am glad I didn't as, the first winter, and not a bad winter at all, we would have froze to death.

I am thankful that I don't have a cent of my money invested in them.

 

Thanks !

What temperature thermostat do you have ?

Mine is 180° and the needle stays about centered on the "N".

Thanks for the spring info.

I am not sure that my bottom hoses ever had a spring; maybe the longer crooked one does.

As my Ford/I-H radiator bottom outlet is on the extreme left side and my Cummins engine port is on the right, I have two bottom hoses connected by about a two-foot section of custom-bent steel tubing.

The first hose, connecting to the radiator, is a simple short 90°; the second, longer, crooked hose may have a spring.

My top hose is a section of a much longer hose that just happened to fit perfect once I cut the needed section out of it; I was sure to record that number in at least a dozen places; as, we carried every hose in the old mom-and-pop parts house out to the truck before we found what was needed.

 

Not sure what is in there, the T'stat has been in there since 1991, when the Ford crate motor was installed, that was 45,000 miles ago.

I'll bet you have springs in both your bottom hoses. I'm no expert on the Cummings. Just know about the need for the bottom hose to have the spring to keep it from being sucked closed, clasping.

My needle on the temp gauge will go above center, near the M until the T'stat opens. Then it will drop back down. Does that in summer or winter.