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Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 35832
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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No heat in my 1995 f 350 with 5.8. I've flushed the heater

Resolved Question:

No heat in my 1995 f 350 with 5.8. I've flushed the heater core and cleaned out the heater box. The twist dial that supposed to control the temp works but still no heat.
Submitted: 1 year ago.
Category: Ford
Expert:  Ron replied 1 year ago.

Hello and thank you for your question,

If you place your hands on both heater hoses out under the hood at the firewall with the engine running and at normal operating temp are both hoses getting nice and hot?

Customer: replied 1 year ago.
they're both very hot but the air coming out of the heater box is barley warm.
Expert:  Ron replied 1 year ago.

Okay if both hose are getting nice and hot and the air inside is not then you have a problem with the blend door and or the adjustment to it. I would try removing the cable from the plenum and see if you can move the door and see if the heat returns, if it does then try adjusting the cables. If it dose not then the problem is with the door inside of the plenum. See the cable adjustment steps in the link below. Copy and paste the link to your browser to open and view them.

Customer: replied 1 year ago.
The cable is working ok but the heat door can't close all the way. I took the plate off that covers the heater core and can see what appears to be some foam rubber in the way of the door. How do I futher disassembled the heater plenum? I also noticed that under the hood and on the heater plenum that there is some kind of air door. The vacuume line that works the solinoid on that door is disingagrated from dry rot. Could this be part of the problem?
Expert:  Ron replied 1 year ago.

The most likely way to access the door would be to remove the heater core which you should be able to with out removing the whole plenum, See the steps in the link below. With the core out of the way you should be able to access the door.

Customer: replied 1 year ago.
I took apart the box that holds the heater core, carefully flushed out the core and removed a piece of foam that was preventing the control door from opening fully. I reassembled everything, filled the radiator and let the truck warm up. Now, even with the heater door all the way open and held open with a c clamp, there is still no heat...... HOWEVER....I lost a little bit of the gasket that seals the heater box and where the gasket is missing, there is some very warm air escaping yet at the defrost and heater vents, the air is still room temperature. The AC clutch is not engaged so is there perhaps part of the ac unit that's jammed forcing the recirculation of the existing cabin air instead of heating the fresh incoming air?
Expert:  Ron replied 1 year ago.

All incoming air with the blend door closed should be coming through he heater core and if that is the case the heater should be nice and hot providing you have good flow through the heater core. If both hose are nice and hot then you should have good flow.

Customer: replied 1 year ago.
OK, so perhaps the engine thermostat is opening to early? It's 66 degrees here today and after running the engine for an hour the temp gauge needle is just covering the "O" on the word 'normal'. This is about 1/3 of the way up the scale. Would that be about right? or should it be hotter?
Could the fan clutch maybe malfunctioning and engaging at a lower than normal temperature?
Expert:  Ron replied 1 year ago.

That should be pretty close, are both hose getting nice and hot at the firewall, usually when you have good coolant flow through the core the hoses will be to hot to hold.

Customer: replied 1 year ago.
They're warm but certainly not to hot to hold. Which is more likely to fail, the cooling fan clutch or the thermostat?
Expert:  Ron replied 1 year ago.

Okay then that is likely your problem, they should be to hot to hold if you want heat in the cab. A bad thermostat or trapped air can cause this type of problem. I think you should take a look at the Thermostat.

Customer: replied 1 year ago.
Ron. I had the misfortune to break the heads off of both of the goose neck bolts on thermostat housing when I went to install the new thermostat this evening. This of course means (since it's going to rain here tomorrow) that I shall not get to it until sun. I'm not happy about it but I was happy to learn about a tool called a 'Titan' Stud extractor. With the careful use of this tool I expect to remove both of the sheared off bolts and install the new thermostat.Obviously I can't fill out your rating report yet but after "we" get this problem solved, I shall give you an excellent rating.
In the mean time, thank you for your patience.
Expert:  Ron replied 1 year ago.

Not a problem, post back if need be and we can work from there.

Customer: replied 1 year ago.
Good morning Ron,
I removed the broken studs on the thermostat housing, replaced the thermostat, gasket and replaced the antifreeze. The temperature gauge now reads a little higher ( to the "R" on the word normal instead of the letter "O") and both of the hoses are too hot to hold for more than a few seconds, but still, no heat. Once again however, that tiny little air leak where the gasket is damaged on the box that holds the heater core, is very hot but yet the air that comes out both the defroster and floor vents is still little better than room temperature.So, looking under the hood, there is a vacuum solinoid mounted on top of the heater housing that appears to control some sort of flap that is between the blower motor and the housing mounted on the firewall. Might that be the sourse of my problems? Other than that, I do live in the country and park the truck outside, and only drive it once a week so perhaps
I have some sort of critter nest hidden in the duct work? Can you send me a 'blowup' of the whole duct system so maybe I could find the place where it's maybe blocked??
Expert:  Ron replied 1 year ago.

If you close the flap on the top of the box doe the air get hot?

Customer: replied 1 year ago.
Ok, So I pried the solenoid on the top of the heater box (and in between the heater fan and the fire wall) open, held it in place with a pair of Vice Gripes and I finally got some heat. Nothing super hot but then it is a small cab and the heat that I'm getting should suffice when it gets colder. I replaced the section of 1/16 ID inch hose between the solenoid and the bundle of wires it was wrapped up in but still no suction. Where is the source of the main vacuum and should I check there or do I want to disassemble the bundle of wires that the vacuum hose is wrapped in and follow it back? I not complaining but it would be nice if I could regulate the heat some instead of having on full blast all of the time.
Expert:  Ron replied 1 year ago.

Is this solenoid in the heater hose? Either way in most cases all vacuum to the heater system comes from the control valve. The controller gets its power from the engine intake.

Customer: replied 1 year ago.
I'm guessing that the solenoid actually controls a vent flap that's between the fan motor and the heater core. With the flap in the open position I get plenty of air but it's all outside air at the ambient temperature. When the flap is held closed is when I'm finally getting some heat. I suppose if I took the fan motor housing off, I could see exactly what's going on inside. Since it's a vacuum control rather than a cable, I'm assuming that it's an all the way 'closed' or 'open' situation and not a variable still, it must be controlled from the heating-cooling panel on the dashboard and maybe that's where the vacuum leak is? I'm not sure, do you have any ideas?I know you must think that I'm beating a dead horse, trying to keep this 20 old truck running but for the next year but "it has to". You see, I lost my very good job of 30 years, when I had a series of undiagnosed strokes 9 years ago. As my brain damage continued from the strokes, the doctors kept telling me that it was Lyme Disease and it wasn't until I was totally crippled and brain damaged to the point where I couldn't even remember my phone number of 27 years, that anyone caught on. It took me 8 years after I was diagnosed to get better but I did and now this truck, along with it's snow plow and a Bobcat skidsteer in tow, are my only source of income. I can't afford to buy even a new "Used" truck but that's ok, with you and the "Just answer" service, I'm sure I can stumble along for a while further. The way I figure it, I'm alive and kicking so I'm still ahead of the game.Thank you very much for your help, patience and putting up with my sometimes, inane, questions, I really appreciate it.
In my previous career I was a newspaper man and although newspapers are slowly dying these days, I do hope to get one last chance to do a guest editorial where I can tout the virtues of "Just Answer" and your help in my recovery.John Ultee
Expert:  Ron replied 1 year ago.

I do not think you are beating a dead horse and I'm going to stick with you till we get you some heat. Let remove the blower motor and see if we can determine which door it is and that will hopefully give some idea where to go next. This is one of those time I wish I could be there to help you get this resolved . Post back when you can and we can work from there and hopefully get you some heat before it gets to damn cold.

Customer: replied 1 year ago.
Ron,I pulled the fan motor and checked the squrril cage, both are fine. The door that's controlled by the vacuum solenoid on top of the heater box and between the fan motor and firewall, controls the "max air" setting and opens a door that apparently recirculates existing cabin air. I fixed all of the visible vacuum lines on the engine but perhaps the control knob on the dash is at fault? How do I disassemble the panel with the control knob on it? It was 14 degrees here yesterday morning and I still have nothing but luke warm air.
Expert:  Ron replied 1 year ago.

See the controller removal steps in the link below,