Heater bypass is an awesome fix!!!

larson · Jul 30, 2015

I pulled the hoses and connected them with a 3 dollar gates 5/8 double male barbed fitting last Sunday and wanted to give it a few days of trial and error and now I can say id recommend this mod to anyone that has to deal with the heat like we do here in Texas. Yesterday the bank tstat read 110 outside and my ac was way cooler then it has been. Unfortunately the very next day my return caps sprung a nice leak but I fixed that too so no more diesel smell in ac vents. Thanks to all that helped or responded to any questions I had dealing with both situations.

IDIoit · Jul 30, 2015

i like to have my heater at the ready incase i experience an overheating condition!

another mod you can do is to use a shut off valve like they did in the bump sides.
then all you gotta do is pull a lever and you have instant heat.

it was 103 here today, no AC, i have 6-90 Ac

BDCarrillo · Jul 30, 2015

6-90??? That rig gets up to 90??

Are there any reasons not to put in a brass ball valve on the heater core supply line? Did it on my 6.4, but the coolant flow was several accessory loops.

Not sure if the IDI is a bit different since the heater core returns to the water jacket and pump.

OLDBULL8 · Jul 30, 2015

On my 84 MH, an electric valve is tied into the AC clutch circuit, when you turn ON the AC that shuts off the coolant flow to the heater. Here is a couple of different ways. Electrical or vacuum.

http://www.amazon.com/s/ref=nb_sb_n...eywords=Vehicle+heater+coolant+shut+off+valve

IDIoit · Jul 30, 2015

BDCarrillo said:
6-90??? That rig gets up to 90??.

90 is no problemo!
i have half a million HP with 3.55's and a ZF

larson · Jul 30, 2015

BDCarrillo said:
6-90??? That rig gets up to 90??

Are there any reasons not to put in a brass ball valve on the heater core supply line? Did it on my 6.4, but the coolant flow was several accessory loops.

Not sure if the IDI is a bit different since the heater core returns to the water jacket and pump.

Yeah you can run valves I was just lazy and didn't install them when it takes 10 min to slip the hoses back on the heater core. To each there own.

Clb · Jul 30, 2015

BDCarrillo said:
6-90??? That rig gets up to 90??

Ummm' YEP it do(flatfooting it down the highway it sings purty nice thru the 4" pipe.

LCAM-01XA · Jul 31, 2015

OLDBULL8 said:
On my 84 MH, an electric valve is tied into the AC clutch circuit, when you turn ON the AC that shuts off the coolant flow to the heater.

Do not copy that exact setup with a Ford light-duty truck! The A/C compressor is engaged when you put the HVAC system in defrost mode, the A/C part of the system is used to dry the air out before pushing it out the vents. If you have the heater bypass valve triggered by the A/C compressor clutch coil alone then every time the compressor kicks in during defrost you will lose coolant flow thru the heater core, not a good thing during cold weather.

BDCarrillo · Jul 31, 2015

So how should we tie in a valve (short of a manual ball valve)?

Vac- Possibly tee off recirc vacuum motor under hood... then no recirc with heat.

Elec- AC clutch circuit would mean no coolant flow during defrost.
Elec- Run a microswitch that the hvac blend door actuates to shut off coolant flow when the temp selector is on max cool?
Elec- Plain old toggle switch

Mech- Run another control cable from the temp selector to a cable actuated valve (used on some 80s Dodge trucks)

Any other methods to tie into the factory HVAC cluster/system?

OLDBULL8 · Jul 31, 2015

That shutoff valve was on there when I bought the 84 MH 15 yrs ago. Didn't see any problem when I did a trip to Texas in -4*F some yrs ago. Fact is I didn't even know it was there until a couple of days ago, when I recharged the AC. :dunno

LCAM-01XA · Aug 1, 2015

BDCarrillo said:
So how should we tie in a valve (short of a manual ball valve)?

Vac- Possibly tee off recirc vacuum motor under hood... then no recirc with heat.

That's how most folks do it, works well for as long as the valve holds up. Which with these valves lately, may not be as long as you'd possibly like it.

You are correct, the recirculation door is closed on the "max A/C" setting only. So it's a pretty decent control device for the shutoff valve as well.

LCAM-01XA · Aug 1, 2015

OLDBULL8 said:
That shutoff valve was on there when I bought the 84 MH 15 yrs ago. Didn't see any problem when I did a trip to Texas in -4*F some yrs ago. Fact is I didn't even know it was there until a couple of days ago, when I recharged the AC.

Not all vehicles are plumbed the same way tho. Especially the ones associated wuth RVs.

IDIoit · Aug 1, 2015

makes me curious how my 98 E350 is plumbed with 2 heater cores.

OLDBULL8 · Aug 1, 2015

IDIoit said:
makes me curious how my 98 E350 is plumbed with 2 heater cores.

Maybe something like this. In the pic the two lower ports, one would be coolant in for the two upper ports that would feed two heater cores, then one of the lower ports wouls be coolant back to engine. Don't really know, but it sure looks that way. Somewhat like a FSV

http://www.amazon.com/ACDelco-15-55...eywords=Vehicle+heater+coolant+shut+off+valve

ToughOldFord · Aug 1, 2015

***Nothing to see here***

Heater bypass is an awesome fix!!!

larson

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IDIoit

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BDCarrillo

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OLDBULL8

Good Morning Ya'll.

IDIoit

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larson

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Clb

Another old truck

LCAM-01XA

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BDCarrillo

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OLDBULL8

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LCAM-01XA

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IDIoit

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OLDBULL8

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ToughOldFord

The Cold Glow-Plug

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