I know on the older trucks it does not hurt anything to put shut off valves on the heater lines flowing to the heater core. will it hurt anything on a 99 or 00 f350?

 

Nope, cold A/C mod is what it is commonly called, can be done with a Ranger or Excursion Heater bypass valve, or just with gates if that's your preference.

I have the ranger valve in mine.

 

Put 2 of those on my heater hoses in F450. The best $15 I spend on my truck.

 

the 02s must be set up differently, I don't have any manual shutoff valve installed and my AC is always ice cold. And I live in one of the hottest places there is. I thought about doing the mod, but I can't see where I'd notice a difference.

 

ok im planning on just putting two manual shut off valves in my heater lines. what size are the lines?

 

They are 1/2" tubings, meaning the outside diameter is 1/2" .
I used 1/2" ball valves with hose fittings on both ends. One of the hoses stretched to be zip-tied to the top of shock absorber bracket for easy access, the other rest on the top of the engine. 2 valves just in case heater core would leak again.

 

You SHOULD notice a difference, but I remember some Superduties had the valve. Rare but was there. Cant remember if its Sport package or Ambulance Prep or something like that, but there was a way to get it from factory, just not common.

 

Same here,don't have to wonder if it's engaging or not..it's either off or on.

 

I noticed little difference in my '01, and I did the same mod in my 1990 F250, and noticed no real change there. Still not sorry i did it, however. I used a sprinkler system brass globe valve (it has shallower/flatter barbs for plastic sprinkler line) and it works great. It has built-in male fittings on each end, which eliminates 2 more fittings and leak points.

 

I put one on my '02 last night...but just one on the line going from block to heater core. My mechanic suggested a ball valve instead of the premade heater hose valve available at the parts house which my BNL, who works with a trucking company that uses heater hose valves, confirmed was not durable. My AC was just not quite as cold as it should be and after reading about this mode, I had my mechanic charge the AC and I put the ball valve in line...the new charge made the AC colder but I also wanted to be able to use just vent air without the air moving over a heated core first...

 

Well I just got done installing two ball valves one on each line to heater core. My a/c is colder by about 10 degrees I have a little thermometer I leave in a vent all the time on 1300 rpm high idle it at about 44 degrees and about 36 degrees running down the road does this sound right? In The past I've been able to get semis and older trucks to run around 10 degrees at idle how come these truck will not get that cold?

 

36F is very good out of the center vents, running down the road.

If you are below freezing at the vent, you will get ice-up on the evaporator, which will then lower the efficiency and raise the temps. When you evaporator ices up, your AC will feel like air being blown over a moist block of ice, which is exactly what it is. Most AC systems have an anti-icing circuit to prevent this.

 

Ok thanks sitting on high idle right now its blowing 40 degrees an it close to 100 out

 

I used a gas shutoff valve instead of the ball valve just because of the smaller handle and more compact design.

 

For the price of the ball valves, you can buy the heater shut off valve from ford, then you can run just the vents without the heater core flowing hot air and defrost still works.