90 LX 5.0L No/Low Hot Air and Radio Display Issue

[LEM]

With the colder weather arriving I've had to use my defroster more and more. However, even well after the engine has warmed up I'm not getting much warm air out of the heater whether I have it on defrost, vent, floor, or mix. The engine coolant level is good, I just topped it off a couple of weks ago. What could cause this and how do I fix it?

Also, the stock radio hasn't had a display for the last few years. The green LEDs don't shine. Any fixes for this?

Thanks much and Merry Christmas!

[fordtrucksonly]

Make sure your selector valve (Control head) dosen't have a vacuum leak causing it to not blow defrost. Normally they will not blow anything else but defrost, but it can do the opposite. As far as the radio goes, just replace it. If you can get me a picture of the radio I might have one laying around I can get to you.

[LEM]

I should also mention that my cruise control doesn't work anymore; could this also indicate a vacuum problem? Where do I begin to look for a leak in the vacuum system?

Thanks.

[fordtrucksonly]

Originally Posted by LEM

I should also mention that my cruise control doesn't work anymore; could this also indicate a vacuum problem? Where do I begin to look for a leak in the vacuum system?

Thanks.

You can air/smoke test the lines or an easier solution, Take a can of brake clean and spray the vacuum lines until you hear a sound change.

[LEM]

Originally Posted by fordtrucksonly

You can air/smoke test the lines or an easier solution, Take a can of brake clean and spray the vacuum lines until you hear a sound change.

Okay, I need a little more info on the brake cleaner test of the vacuum lines: where do I spray it? What kind of change in sound should I listen for?

I checked the "temperature door" (the damper controlled by the temperature knob though a cable) and it is moving okay. When I have the fan on the slowest speed I do get some warm air through the vent and the floor - I need to double check to see if I get it through the defroster as well, but let's assume I do. When I increase the fan speed I lose the warmth and it seems to be blowing ambient air no matter what I have it set on (floor, vent, mix, defrost).

The fluid level is good. My engine temperature gauge reads normal, so I don't think it's the thermostat, though I plan on checking it tomorrow.

How can I troubleshoot the selector knob to see if it's working properly?

Is there a fluid valve somewhere in the heating system that could be stuck? Does anyone have a piping schematic for the heating system?

Thanks for the help.

[fordtrucksonly]

You should be able to hear the vacuum, kind of a whooshing sound, when you spray the lines with brake clean, once you hit the spot of the leak the pitch of that sound will change.