Hi all. New to forum. I tried another forum but no one seems to respond. Hoping to get some answers here. Just picked up an 87 150 and have found the following few problems. (Chilton no longer has a "troubleshooting" section...taking that POS back). Anyway here we go...

No heat. AC blows cold, but there's no heat. Possible problems and fixes?


Cheers

 

Not sure if that model uses a flow switch in the heater coolant line to control flow or not. Check the hoses running from the heater core and see if there isn't a valve in one of those lines with a vacuum line or cable connected to it. If not then you don't have a control valve and heat to the inside of the truck is controlled by a diverter door in the plenum. If you don't have a valve both lines should be hot at the heater core. If not then you probably have a plugged core or coolant isn't flowing through the hoses. Make sure the coolant level is topped off in the radiator. If you do have a control valve make sure the vacuum line or cable is connected. If it is and you don't get any heat, disconnect the vacuum line to the valve and with the heater controls to heat and highest temperature check for vacuum at the vacuum control hose. If it is a cable check to see if the cable is moving the control valve. All of these tests need to be done with the engine at idle. If no vacuum then you need to track down a vacuum problem. If there is vacuum reconnect the hose and see if both hoses are hot indicating coolant flow through the heater core. If no flow probably a bad control valve or plugged heater core. If the heater core appears to be plugged you might be able to open it up by removing both hoses from the core, getting a short piece of heater hose and attaching a plastic female garden hose connection and connecting the hose to it and turning the water on very low to see if that clears the blockage. If it is blocked tight you will need to replace the core. If water flows repeat the process through both sides of the core until water flows freely. Don't turn the water on full force or you will probably pop a leak in the core since the seams are soft solder and can't take much pressure.

John

 

Wow. Thanks John. Sounds like a thorough process. I was hoping it was going to be something simple like a loose wire


Thanks for the info.

Cheers

 

87 econoline,302/auto, with AC, AC & heat control panel in dash not contigent to one another,i.e. AC not on when heating as in newer cars.
Problem. Replaced a leaking heater core. Before replacement the core did heat very well. Replaced the core with exact replacement. Less than luke warm air. The inlet and outlet heater hoses hot. Removed the hoses at the manifold and the pump and not clogged and water pumps out of the manifold fine.Water flows through the core fine. All heater controls work. I removed the vacuum operated heater valve and replaced with a coupling eliminating the valve. Same result,, very little heat.
The only thing I see that may reduce or transfer the "flow" of more water to the core is the "tee" in the pump line over to the fuel injection block. Dont no what controls the diverting of the flow throuigh the F.I. block, if has a control at all?
Could the % of antifreeze/coolant be too much to not allow transfer heat from the core?
The heating was working fine with the old core(had pin hole leak).
Baffled.

 

Hey John - There is a valve. The hoses leaving the valve were not hot. I pulled the small dia vacuum hose off the valve and the hoses got hot and started pushing heat thru the system. The vacuum hose was not plugged at all. Once I put the vacuum hose back on the valve, the heat stopped. What am I looking at now?? Thanks John

 

Dal,

Sounds like the vacuum is being applied to shut the valve so you will need to check the temperature control circuit to find out what causes the vacuum to apply for cool operation when the system should be calling for heat. Does that F-150 have a temperature sensor in the dash? I had a 86 Grand Marquis that had the sensor and it controlled the vacuum output. It had a cable connected to it as well as a hose from the blower plenum to cause air flow over a bimetal thermostat that controlled the vacuum flow. The cable was connected to a temperature slide control on the dash that worked from blue (cold) to red (hot) as you moved the control and the cable would slide, the valve would rotate the bimetal sensor so as to adjust vacuum flow as the bimetal contracted or expanded. You might want to check and see if your F-150 has something like this in the circuit. If it does you should be able to check its operation. Might have to remove the top of the dash to get at it. You can identify where it is located by just looking for a small opening in the vertical front of the dash just below the dash cover. If it doesn't then I would bet that the vacuum flow is controlled by the temperature control at the dash. Let us know what you find.

John

 

My heat in my 97 Ranger went out a few months ago. I've checked all of the obvious problems that i know how to i.e. thermostat and heater core. The supply and return lines to the heater core both get hot when the thermostat opens up so i have to figure that its working okay. I've read about a lot of problems with the blend door in this truck but they always have problems with having constant heat as opposed to cold air. I did change the, for lack of better terms, back of the hot/cold ****, thinking that maybe since it went out in the summer that it might have just been stuck on cold there. I'm at a total loss and i can't find anything explaining the heating system in a way that i can understand it. Any help at all will be greatly appreciated. Thanks.

 

If the heater core supply and return lines are getting hot (check right at the firewall, as close as you can get) then it is probably the blend door stuck in cold.

 

Do you know of any way to fix a broken blend door without having to pay out the nose? i found one "quick fix" online but it seems a little to good to be true. Free Ford Blend Door Fix

 

Those guys pretty much know what they are doing....looks like a good fix to me!