lexxluther11

I just replaced a bad heater core on my truck but it will still not blow hot. I checked the core and it is getting hot and I am blowing air but nothing hot.. any suggestions?

Alex

65mechanic

Welcome to the forums! If you've ruled out that the core is getting hot, and yoyr blowing air then there's one more thing. Make sure the vent is open to blow across the core itself. I'm not sure exactly how the interior vents operate but your cables might not be opening to the core, thus just recirculating truck temperature air.

0927

My '89 has A/C, all vents and doors are vacumm operated. I currently have the same issue. My truck sat for 19 years before I bought it, all the vacumm lines to the heat & AC are dry rotted. I started replacing the easy ones I can see and now have a little air moving into the cab, but not much.

5Rangers

There is a cable attached to the lever you adjust to set the desired temperature. It goes to a mixing valve which gets air that has passed through the heater core and mixes with the other source, either AC or outside. If this cable was broken or one end not attached then you would not be able to adjust the temperature of the air coming in the cab. I have an 88, the cable is notorious. It either breaks, disconnects or breaks the linkage it is attached to at one end or the other. It is easy to replace, simply pull the climate control head out of the dash, you'll see it right away. If your problem is not on that end, pull the glove box and follow the cable to its linkage.

65mechanic

+1

jrh5610

Check the white vacum line underneath the hood on the passenger side. It goes to a cylinder in the corner of the firewall and inner fender. Normally those will dry crack. Dig back into the harness where it comes out and cut it off. Get you some 5/32 vacum hose around 20" should do it slide one end onto the cylinder the other end onto what is left in the harness. That should do the trick.

lexxluther11

Thank you, I would have never of thought of that! I went out and checked the cable and the wire that runs through it was bent before it went in and so I straighten it with a pair of plyers and now it works like a charm... Thank you so much for your help!!

Alex

ymeski56

I think what your referring to changes air discharge path. Defrost/ dash vents...

5Rangers

Glad I could help... Good job...

Zackpak

My 1988 f-150 heater isn't working I can hear the blower but I don't feel anything through the vents... Even after I switch them to floor or panel still nothing