Just finished a 3-400 mile rounder in Northern Michigan.

Truck held a great steady temp on the gauge. Cab heat was minimal at best.

5 1/2 hour white knuckle trip back home that generally takes 3. Snowy roads and cars spun everywhere. (no trucks lol)

Question being, do one of these guys control cab heat and the other op temp?

I have motorcrafts on the shelf I haven't done yet. I am going to do them this weekend, but would that be something that may be the issue?

Looking at the diagram for the cooling system I find no cause toward either thermostat being the cause.

Engine at 185ish, cab heat maybe 80 tops.

Just put in a new radiator, updated hoses........new motorcraft gold premium coolant.

Curious? Fan speed and all else seems great but even on high on both zones, frozen feet!

Just wondering if anyone else suffered the symptoms and what the cure was.

Denny

 

Interesting, yet I have an idea based upon my experience.

Look at the coolant level. In cold temps mine is on the lower mark for the minimum and I can heat the crew cab no problem. When my coolant was on the higher mark I had challenges keeping the cab warm.

In general, my thermostats are keeping 195F when the outside temps are 30F and abround 185F when temps are below 20F.

My coolant system has been flushed and filled with a CAT-1 Extended life coolant.

 

Thanx Copper,

Just went out and looked. It's standing at 1/4 inch above min in the degas.

I'll still go forward with the thermos and report back.

Still can't find any diagram for the cab side and if it relates to cabin air in the instance of the seperate therms.

Puzzling me.

Thanx for the input.

Denny

 

Just looked at Fritz' diagram and it does look like the upper therm is the guy that controls the cab heat but will do more digging.

All hands on deck


Denny

 

My truck normally runs around 194 degrees when on the highway that long. Replaced the thermostats around 2 months ago and it will burn you out of the truck now.

 

Replaced both of mine back in the fall. On cold days, that being temps below 20, the heater does act funny. It will put out warm air while heating up, say 150 degrees on the coolant. But will bounce back and forth when the temp gets up to the 185 to 205. The thermostat will open around 200 to 205, and the heater will be cold until it opens, for some reason. While it's open, warm air come out, then the thermostat closes at about 185. Then it gets cold again. It does this until the truck gets up to a constant temp of around 195. Once there, heater acts normal. It may take it 30 miles of highway driving for that to occur though.

 

We'll here we go, first off do you have gauges, not them things on the dash because they aren't acculturate. First off it's kind of a screwy set up but the way I see it both stats do the same thing either stop the flow or let it flow, they both dump into the top radiator hose so one dosen't do anything special for heating the cab(that I can see). Secondly these things are made to cool, not heat,with a winter bra mine will get to 193 in 12 miles or so going 65 in current Michigan weather. That's with it being plugged in for 2 hours before work, if I'm being weak and say stop at McDonald by the time I get my order I've lost 15 degrees in engine temp. If it is really cold I've actually have had the high idle kick on. In the summer it runs at 193/194 all day long, I replaced both stats about 5 years ago, it's always acted the same.
150 must be the magic number for us with climate control because that's when it really tries to offer up some heat, mind you not anything like my son's 2008 f250 v10, but enough to make it comfortable,no frozen toes. Sorry I guess I got long winded but even in that snowstorm (that we were in on the opposite side of the state by Clare) you should have 194 ish degrees and heat. Hell even at 185 you should have heat, I would go for the stat's and then check out the action. Do you get good heat at the defroster, if so then maybe check out the blend doors. I've never checked but you should be able to grab the hoses going to the heater core to see if their hot or not. Anyway you cut it, their made to cool, not heat, that's why you must have heated seats, gloves, and maybe in your case some socks you can plug into the lighter.

 

check coolant / water ratio. more coolant / less water provides low freezing point...but...does not transfer heat very well .

I'm recalling you installed a coolant filter....normally the hose to the filter gets T fitting off the cabin heat hoses on the pax side and then the filte return goes to a T fitting by the radiator degaus hose. clamp the coolant filter hose off with a small piece of rubber wrapped around the hose and a small vise grip pliers. then chek if the heat is better with the hoses clamped off.

other option...depending on your climate...look into the ford grill bra which blocks air from going into the radiators and as a result...cab heats up quicker.....obviously not a good thing to install during towing.

 

Just an update:

Wife is the driver. Various scheduled appointments out of town so I have not changed the stats yet.

Studied up a bit and still can't get a definitive reason why the cab heat is suspect.

I did check and confirm the posts. The supply to the core is definitely warm to the touch. Blend door seems perfect in all positions. I put a lil more coolant in to the max mark to see if there is a substantial diff but that was today and the truck is back on the road tomorrow.

I'll advise on the progress.

Thanks for the help guys, really appreciate the input!

Denny