Heater Problems....

[Rangurr]

Okay, so here's the deal. Freezin' season is rapidly approaching out her in Utah and my heater is freaking out. Last winter (granted this was in a different truck but they're the exact same engine and everything) the second my engine heat started registering, I could turn the heater on and basically have the tiny regular cab instantly warm. This was consistent no matter how cold it was outside. Now, it's getting down to about the mid 40's and I have tried to start using the heater a little bit every now and again but it's having some issues.

When I start the truck, obviously it blows cold because there is no engine heat. When I turn it on as the engine begins to heat up like I used to, the thing still blows cold. Once the engine heat hits mid gauge, where it consistently sits, it still blows cold. It will not blow warm until about 10 minutes after the engine has reached running temperatures. This is a bit annoying but I can deal with this. The part that I can't deal with is that when I coast for a few seconds (Clutch in or out - it doesn't matter what the engine rpms are being held at) or stop at a light/stop sign, the damn thing starts blowing cold again!!!

Anybody dealt with this before? Any ideas? This is really going to suck once ski season comes around!!!

 

[Earl43P]

I had a similar issue with a 2.5.

I replaced the heater diverter valve or whatever it is called. Basically, the valve where the coolant lines go to. On mine, it was vacuum controlled and not an expensive part, like $23. Look up "Part # 74859" on RockAuto.com to see that valve.

It controls the flow of hot coolant to the heater core.

 

[UrbanRedneckKid]

One of 3 things typically cause that. Low coolant, air bubble in system, plugged heater core.

Do you hear water noises in the dash when you accelerate?

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[Rangurr]

I originally thought the same thing about the HCV. I replaced it but it didn't help.

One thing I should probably mention is that my heater box melted between the exhaust manifold and heater core. I replaced the cover with one covered in heat-shield and it hasn't had problems since.

Is there any chance this either screwed up, or is an indicator of a bad heart core??


I'll check for water noises once I'm out of school.


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[RonD]

Reads like flow thru the core is the issue.

Melted cover shouldn't have effected the core.

I would try back flushing the core since you have already replaced the HCV.
Next time you have a chance after driving the truck(so engine is warm), open the hood and feel the two heater hoses where they go into the core at the fire wall.
The hotter of the two is the IN hose, the other is the OUT hose.
If you have had the heater on inside they should be almost the same temp, but one will be warmer, if the other is alot cooler then core is clogged, or the hose is....

You don't have to drain the cooling system to do the flush but you will need to add coolant after you are done.
After engine cools off or on another day, remove the IN and OUT hoses at the engine end.
Point the IN hose down at the ground, hold flowing garden hose to the OUT hose and start the "back" flushing, also watch what kind of flow you have.
Heater cores are just like radiators, larger tube splits into several smaller tubes, smaller tubes get clogged by debris coming IN thru the larger tube, "back flushing" pushes larger debris back out the way in came in.

If flow is low then you can mix some CLR(or vinegar) with some warm water and funnel it into the core, let is sit for 20 minutes then repeat back flush.
If flow does not improve then it is time to replace core.

 

[Rangurr]

Okay so, thanks for the great suggestions. I agree with most everything here but, surprisingly, that's not what fixed it...

So, I was feeling the hoses to see what was hot today and 2 felt cold so I assumed the HCV was freaking out. I checked and it was operating as it should have been. I then noticed that the A/C was kicking on and off no matter what the A/C was set at on the headunit. I unplugged it and filled the truck back up with antifreeze (slightly low) and it instantly heated up. Everything feels like it's working as it should now. I'm assuming that the Freon was low and that was kicking the pressure switch on and off. I seem to remember somebody telling me that the compressor kicks on and off to prevent damage to the system while the heat is on but I can't quite remember. Should I be plugging the sensor back in and letting it do its thing??

 

[adsm08]

Sounds like your temp blend door is damaged.

 

[Rangurr]

Sounds like your temp blend door is damaged.

And how did putting antifreeze in and pulling the (high?)pressure sensor for the A/C fix it?? -That's not meant to sound like I'm discounting the idea, I'm just curious how you came to that conclusion.

 

[RonD]

Okay so, thanks for the great suggestions. I agree with most everything here but, surprisingly, that's not what fixed it...

So, I was feeling the hoses to see what was hot today and 2 felt cold so I assumed the HCV was freaking out. I checked and it was operating as it should have been. I then noticed that the A/C was kicking on and off no matter what the A/C was set at on the headunit. I unplugged it and filled the truck back up with antifreeze (slightly low) and it instantly heated up. Everything feels like it's working as it should now. I'm assuming that the Freon was low and that was kicking the pressure switch on and off. I seem to remember somebody telling me that the compressor kicks on and off to prevent damage to the system while the heat is on but I can't quite remember. Should I be plugging the sensor back in and letting it do its thing??

A/C compressor comes on when Defrost is on, it dries the warm air blowing onto the windshield defogging it, or when A/C is turned on.
It shouldn't cycle on/off otherwise.
A/C isn't damaged by heater being on.

If A/C is on and it cycles on/off then it could be a pressure issue or there is an often seen issue in Ford compressors where the "air gap" in the compressor clutch gets too wide, so clutch can't hold tight.
Google: ford ac compressor air gap

 

[Rangurr]

Ah, okay. I think it was explained to me as a way to keep the freon moving in the system while the A/C is not in use but this was cycling about every 2-3 seconds and that seemed wrong. Another possible problem with this is that the freon level is really low. I know with the A/C on, the low freon would build pressure, kick the compressor, and then lose pressure, therefore kicking it back off. It would repeat this over and over. It is doing that on A/C at this point by the way. I just don't understand why it would be kicking on and off during plain heat (not defrost). I'll look up the compressor air gap and see if I find anything that solves my problem.

Anybody think it's too late in the season to justify re-charging the system? I'm pretty much done needing cold air for a while anyway. Plus, the thing likes to leak.... pretty quickly too, and I don't particularly want to go through the whole system at the moment.