Installing valve in water line from head to heater core

40* on my '03. I can tell if the refrigerant level is off if the vent temp goes above 41*, and oddly enough, if it drops below 40*. I think 53* vent temperatures would be almost unbearable, at least here in Texas. Maybe up north it could work, but not here.

 

40-42° on mine too.

 

Second law of thermodynamics suggests there must be a benefit. The heater core is not perfectly insulated by the blend doors within the HVAC box. In stock form the heater core is typically around 180°F. It WILL heat up the blend doors and the air flowing across the doors WILL pick up that heat. All that's left to argue about is the magnitude of the benefit. Other vehicle manufacturers have determined that, at least in their more luxurious lines, it is worth the effort and have implemented heater core bypass valving. Dodge didn't see fit to incorporate it in their trucks. Doesn't mean there is "no benefit." Remember, in our case Dodge was building a truck, not a luxury vehicle. Dodge also didn't include a lot of other upgrades that many of us have had no problem adding; like better floor mats, additional sound deadening, cabin air filters, adequate fuel filtration, bigger lift pumps, cooler looking air horns, bigger turbos, fancy wheels, fuzzy dice, and the list goes on.

Heater core is AFTER the evaporator. ALL air goes through the evaporator then in full cool mode all of the air travels around the top and bottom of the heater core, separated from the core only by the blend doors themselves, thus some heat WILL transfer from the core to the doors to the treated air. How much this heat bothers you is also a matter of degree.

And, yes, as Ozzy points out, it adds another potential failure point. You have to weigh that going in. But as you weigh it remember that these valves and hose clamps are really simple, have been pretty much perfected over the years and therefore are generally pretty reliable. Having weighed it myself, it's on my "to do" list, but it's way, way down there still.

And if you do it to your third gen, please gather and post some empirical data for the rest of us.

 

I have to disagree on one point here. There may be a benefit, but there is always a tradeoff. Anytime you are working with complex systems there is a tradeoff. So it's not the magnitude of the benefit that is the point of contention. It the net gain/loss between the benefit and the risk. As @Ozymandias stated, it's a point of failure. Therefore it's a risk. So the argument should be does the benefit outweigh the risk. And on that point, I would argue that it depends on what you use the truck for, and how you will be impacted should the benefit come into conflict with the risk. Do you frequently travel long distances that could result in a breakdown far from home? Would it matter if bypassing the heater core took 10,000 miles off the life of your engine? Those are the kind of things that each owner has to weigh for themselves.

 

It was a very hot topic (pun intended) on another forum I frequent. Somewhere in the 200+ posts category. Eventually Ram came out with a TSB to replace the entire HVAC box under the dash. After seeing other members who received the TSB and the “just ok” results gained and the idea of the interior being ripped out of a new truck turned me off to it. I opted to do the shutoff instead. 53 was not comfortable in the humid northeast, it wouldn’t really condition the air. Lack of condensate on the ground was proof.

 

The chance of a heater hose valve failing is almost imperceptible as they’ve been used since someone thought of using engine heat to heat a vehicle cab. Maybe if someone bought a piece of junk valve?

And if one were to use a bypass valve instead of a deadhead valve, the theory of certain cylinders suffering from lack of coolant flow is defeated.

 

By the way, for how many years did you drive your former 03 without that added valve?

 

I'm not really thinking that the valve itself is the primary or most likely point of failure. For example, in looking at the picture of the Joywayus valve that @BigPapa posted I see no less than 14 potential points of failure, with the valve itself being the least likely. At the top of the list you have the 4 hoses. Then you have the 8 connections, one at each end of the 4 hoses. The valve knob/seal is second to the bottom; unlikely to fail but not unheard of. At the bottom of the list is the brass body of the valve itself. I think we would all agree that the chances are almost nil that under even extreme operation the brass is not going to crack in the absence of a serious traumatic event.

So when you juxtapose the above potential failures with how you use your truck you can get a clear picture of what you need to protect against such failure. If you're on the road, far from home a lot you should at minimum have 4 spare hoses and a few band clamps on hand. That takes care of 12 of the 14 potential failure points. The final two can only be remedied by having a spare valve (and the necessary tools to change it) on hand, though we can all agree that those are very unlikely. But 4 additional hoses and 8 connections are well within statistical probabilities of failure. And I would still be concerned about standing water and coolant in the heater core. Are chances low that it would cause problems? Maybe. But the fix if it does is a pretty involved repair.

 

Ah, yes! The worst kind of failure point: Manufacturer design failure! No way to protect against that. I guess the question to ask then is have all the AC problems been fixed on the 4th generation trucks, or is it still a problem?

 

20

 

In the 20 years of driving my 03, I had one failure with the heater lines, and that was the steel fitting that is under the rear of the exhaust manifold. It's basically a sweeping L with a bracket welded to it that bolts to the side of the block or head. It's the return water line from the heater core. Mine rusted so bad that pieces if scale came off, causing a massive leak. I could not get a new one immediately, so took it out and brazed up all the leaks, primed and painted it and reinstalled it. Never had trouble with it again.

 

I did the Ball Valve shut-off probably 12-14 yrs ago. I open it all the way in the winter, and close it off, about 80-90% in the summers. It seems to keep.it a little cooler. I never had any issues with the heater core, or overheating. Probably because I don't keep it completely closed. If you guys want pics of it, let me know.

 

I'm of the opinion that pictures, like free beer are never a bad thing. I say post them. But I also have to admit that in this entire thread I never once pictured only partially closing the valve. That may be an actual valid compromise.

 

For all you naysayers worried about reliability, today's BMWs, Mercedes, Jaguars, etc. designers have evaluated the tradeoffs and decided in favor of the added complexity and risk for the nominal added benefit of reduced heat in the HVAC box. In evaluating those tradeoffs, I'm sure they have a lot more information at their disposal than we do.

But, not to be outdone by modern BMW, Mercedes and Jaguar, in doing a bit more research I have found a Mopar part number for a similar heater core bypass valve: 3849199 See item 17, VALVE, Water (4-port) 2,5 Engine. This part is for a 1990 Dodge Daytona. Here is the aftermarket replacement today. It won't easily work for our trucks since it's vacuum operated.

BTW, the same part was also used in Chrysler LeBarons and New Yorkers, and Dodge Daytonas, among others. These don't appear to me to be model lines that Chrysler would have wanted to seem "less reliable!"

Clearly the tradeoffs worked in favor of adding the valve for Mopar engineers back in 80's and 90's. Might not be saying that much, but it was a stock design. Also, I did not look to see if modern FCA vehicles continue to do this, but I would not be surprised. But it does suggest that reliability issues are probably NOT what kept the valves off the Gen 3 pickup trucks. My guess is Chrysler's desire to separate luxury vehicles from lower lines (i.e., snob appeal - they didn't put these valves in the Dodge Darts or Plymouth Horizons of the same era either) and the added cost nixed the notion. I mean, our trucks were designed for work; even the Gen 3 Laramie line wasn't really all that luxurious.

However, electric versions are available that look an awful lot like these Mopar style units. Here is one from Old Air Products, and another from Thermotion. They look like good fits to me.

 

Was there a functional problem with the HVAC System throughout these two decades that makes you to want this hack? Just asking, I still want to understand what brings you to this topic.

 

Just an A/C system that doesn't blow as cold as it should. I think mine has a little to do with Blend Door issues too.

 

My concern doesn’t have anything to do with parts reliability, but rather the fact that 5/6 already run hotter than the other cylinders and flow thru the heater core improves flow for the back of the block. I wouldn’t want to decrease that flow in the heat of the summer.

Then fix those issues. A 3rd Gen shouldn’t need a heater core bypass valve in summer. I was able to get temps of 41° out my drivers side vents on a 126° day in Phoenix, and that was slightly low on refrigerant since the passenger side was blowing warmer. Temps equalized once I added some refrigerant back into the system.

 

FWIW... If there was a real benefit, they would've included a shutoff valve from the factory like my old Chevy's from the 60s and 70s have. I have never had an issue on any of my RAM trucks with A/C not being cold enough, even here in the southeast... not an issue, and not worth the effort and associated risks that have been mentioned... JM2C.

 

The AC has always worked, but was never as cold as it could have been. The large black dash in my truck always absorbed a lot of heat from the sun and made it difficult to stay cool on hot sunny days, especially when stop and go driving all day, and getting out of the truck every half mile or so. A dash mat made a huge difference to alleviate the sun on the dash.

 

Poor AC has been discussed since about '94 when Dodge did away with the shut off valve to the heater and continues to this day. Nothing great about my '21 Ram.

Blakers, you might remember this thread.

https://www.turbodieselregister.com/posts/2353383/

http://www.dieselbombers.com/dodge-.../29176-3rd-gen-tech-colder-ac-under-25-a.html