Busboy

Most know how "marginal" the A/C is in the second gen trucks it's bad enough up here in the summer but it must be pretty bad in the hot US. Anyway I was wondering if anyone has installed a water shutoff to the heater core. By using the same vacuum source as the max AC recirc door we could shut off the hot water supply through the heater core right when we need it the most. I talked to the dealer back in 2001 and after a long drawn out discussion they said it was not possible. I had forgotten about the subject until today while rooting through my parts I found a brand spanking new vacuum water shutoff vlv in among a bunch of switches while looking for a high idle solonoid.
Anyway has anyone done this or even a manual shutoff or does anyone know of a reason NOT to do this?

GFB

You could fab up a simple H pipe with a bypass valve to put in line before where the lines go through the firewall. Wouldn't hurt anything. I would suggest a bypass rather than a block off.

The a/c in my truck is about the best of any vehicle I've ever had. I didn't know they had a bad reputation.

I'm not totally sure what you're getting at though. When the temp **** is all the way to the cold side you aren't putting any air past the heater core anyway.

biododge1

i may be wrong, but i think the recirculating door is electrically operated and not vacuum

Busboy

I'm not saying the AC is bad, it just doesn't throw ice cubes at you. On the newer trucks Dodge went with a much larger condenser to improve the cooling. If this truck had electric radiator fan/s it would greatly improve the AC at start up. In very hot conditions on the hi-way towing the hot coolant still passes through the heater core which is inside the cab. Even though the air flow doesn't pass through it, the heat still radiates into the cab so the AC has to fight the heater system as well. I searched the threads and found some reference to this in the first generation truck section and sort of got the impression that this was standard on the first gen trucks. I remember many older vehicles that used this system and was surprised to find it missing on my truck. It would be a simple mod as the only thing electric is the blend door, the other doors are vacuum.

JSPulliam21

www.dieselsite.com sells a kit or the Powerstroke guys. Maybe you could build one like theirs. Here is a link.

Tommy93w350

I've done this on my truck with two different configurations. You can not block the circulation totally off. Trust me, you don't want to do this. It does make a huge difference during the summertime. During 95 degree heat, my ac runs on low on a trip, it freezes my wife and my feet!

First the easiest, take the heater hose off the core from front of the motor and connect it to back of the motor. You're simply bypassing the heater core and re-routing back to the block. The bad part, every winter you have to re-connect the hoses.

Second, I created a H valve with 1/2" ball valves, nipples and extra hoses. I'll have to take a picture to describe though. Very simple, get all the valves and hoses from the hardware store. I'll try to get pics tomorrow.

Once again, do not block off the water circulation, just re-route it.

Busboy

Thanks for the input. I thought of a manual shut off as it would be easy to rig a bypass like on the hot water tank of an RV for winterizing, but would prefer something that is operable from inside. You say don't block the flow, do you think it will cause hot spots in the head area? Like I said I sorta thought this was a stock thing on the first gen trucks? I'll post a question in the first gen section and see if I get a reply.

AggieJustin

Where did you connect the hose to feed back into the rear of the block? I've considered doing this on mine to try and get some extra cooling from the A/C. I just haven't looked close enough at it yet to see where I'd plumb it up at.

Joseph H. Smith

I don't know what condition your a/c's are in but they must be weak at best. I have a 98 quadcab and I work in the country of Panama where it is extremely hot almost everyday of the year and I am constantly being asked to turn down the a/c. Any little problem with the a/c will impact its performance. Partially clogged evaporator, partially clogged resticter tube, too much oil in the system, low on gas, blend door insulation is failing allowing the hot air to pass around the door even though it is closed. I fixed that one by putting new foam strips around the door as the original foam dissappeared when you touched it. Also if the blend door is out of adjustment and is not closing completely. Weak blower motor, pinched line. If you block off your heater core for the summers it will corrode. That is one of the reasons that the shutoff valves were discontinued. I had one on my 70 Nova. It would sit in one position all summer and then when I finally would turn on the heat the valve had deteriorated from sitting in one position for so long and leaked. Happened more then once. I have not had to change my heater core on this truck yet but I did have to change the evaporator as since this truck does not have an air filter it got clogged from dust sticking on the wet fins reducing air flow and making it longer for the evaporator to dry after use. They rust from the outside-in. When I cleaned the old evaporator all of the corrosion was on the fins that were covered with dirt.

Busboy

Like I said earlier I'm not saying they are bad, just they don't throw ice cubes at you like some vehicles do. If it wasn't a "marginal" system design Dodge wouldn't have increased the size of the condenser on the newer trucks. For the most part it's ok, it's just when extremely hot and towing at hi-way speeds with a cab full of people it's "marginal" because of the heat radiating off the heater plenum. By installing a s/o vlv that operates with the recirc door would mean it would open and close all the time, the only time it would close would be MAX AC and OFF, the rest of the time it would be open. I changed the evap core recently due leaking on the bottom, the old one was clean, I also installed a new dryer at the same time, the condenser is clean and the sys is fully charged, it runs a drivers side duct temp of around 40F which is not bad.

JSPulliam21

That link I posted uses a vacuum actuated valve. If you tapped into the MAX A/C vacuum line it would only shut off water supply to the heater core when MAX A/C is selected.

Tommy93w350

Run one hose from the the back of the block to the front and completely bypass the heat core (we'll call it block hose).

Now, run one hose from the heater core to the block hose, put a valve at the end and Tee it into the block hose.

Run a hose from the other heater core to the block hose leaving room in between both heater hoses. Install a Tee to the block hose.

Install a valve between both heater hoses on the block hose to divert water through the heater core.

You should end up with one valve on a heater hose and one valve on the block hose.

During the summer shut off the heater core hose and leave the block hose open.
During winter, open the heater hose and shut off the block hose.

The flow is never shut off just diverted through the heater core or back to the block.
*********One should always be on so the coolant will flow***********

To motor
I
I
I Heater Valve
I----X------------------------------------ Heater Hose
I
I
I
X Block valve
I
I
I------------------------------------------Heater Hose
I
I Block hose
I
I
I
To motor

EverydayDiesel

I have after market oil cooled only turbos. Can I just cap the line right before the heater core?