Yh-380 vacuum switch alternative solution found

[Jaded]

Quick update for folks interested in alternatives to the Yh-380 vacuum switch.

Ordered what we were told was a YH-380.

Received the heat only switch...

Out of desperation and stubbornness I took the switch apart to determine compatability  between it and the parts from our OEM ac/heat switch.

Turns out the vacuum bodies of the switches are nearly identical except for a single vacuum port behind the sliding valve plate and the valve plate itself (and obviously the extra two conductors for a/c circuit.)

Conveniently there just happens to be a very slight dimple where the additional port should be on the vacuum body.

So:
After removing the cover that holds the sliding valve plate to the back of the vacuum body.
I used a pin (like the kind you find in new button up shirts) with a little heat applied and slowly pressed through the dimple to add the port. Being careful not to leave any extruded material around the edges of the new port so as not to damage the rubber on the sliding valve plate as it moves back and forth.

Reassembled the new vacuum body with the valve plate from our a/c-heat switch. Back on to the OEM a/c-heat switch body (being mindful of the annoying little ball bearing that needs to sit on the detent spring between the switch slider and the vacuum body).  Also cleaned and applied a dab of dielectric grease to the contact slides on the switch body while I was in there.

Voilà

Blend doors all work now. A/C and max settings also work as they should too. Although rhe a/c is not connected with a belt so can't confirm entirely as that circuit is offline atm..  project for another day.

I'll try and get some picks of the specifics, but it is fairly self explaining for the adventurous and stubborn DIY'r.

Total time: about 45 mins to swap components. (A bit fiddly and tedious and my hands shake from nerve damage)

Tools needed: a set of mechanics picks, fine gauge needle, bit of assembly grease safe for plastic and rubber.

Side note: someone should model this thing and start 3d printing them...

[Gary Lewis]

Well done!

By the way, if you do the same thing to Port 1 you can run a vacuum shutoff valve to stop the flow of coolant to the heater core in both Vent & Max A/C.

[Jaded]

Gary, Noted with thanks!

Part number for that mod?

On the topic of Vacuum:

Has anyone had any issue with the silicone vacuum hose kits? I like the idea of using the fancy colored hoses as that seems an ideal way to keep track of what's what, but unsure if the silicone material is prone to any sort of failure or poor performance.

Seems like all of what I have read so far is from the perspective of before purchase and not the 3 years later perspective I am looking for.

[Gary Lewis]

I'm not sure what part you are wanting the PN for.  Maybe the valve to shut the coolant off?  If so it is on the page at Documenation/HVAC/HVAC Systems and then the Heat Shutoff tab and then the Vacuum Valve tab.

But, by the way, heed the caution on that page, which says "However, it only works on trucks with the 1980 - 82 HVAC controls as the 1983 - 86 controls can't be easily modified for this use.  But, you can swap the earlier controls into a later truck, as explained on the Swapping Controls tab above."  Anyway, read the page.

And if you don't want to make that mod you can tap into the vacuum line under the hood that goes to the recirculate door and use it to control the shut off valve.  The recirc door closes in Max A/C so you'll not have the heat shut off in Vent, but you will in Max.

[ArdWrknTrk]

I'm looking to now bypass my heater core.
(Actually, I should verify the motor by the hood hinge is working, and check the foam on all the flaps)

Heat sneaking into the cab, and I've never had AC, but (as you know) I have plenty of firewall insulation.

Maybe just a manual valve....

[Gary Lewis]

I don't know how the vacuum system works on an '87 but suspect it is just like an '86 and the recirc door only gets vacuum in A/C and Off.  W/o A/C you probably don't have that position so getting vacuum to the valve isn't easy.  A manual valve is easy.  

[ArdWrknTrk]

Well, I checked the hot-cold door actuator and it is working.
So, I guess I need to take out the heater core and reseal that door.

Do you have a p/n for a manual bypass valve?

[Gary Lewis]

Unfortunately no.  We have a tab for it on the page at Documentation/HVAC/HVAC Systems but no entry.  So if you find one please let me know and I'll update the page.

[ArdWrknTrk]

Right away Captain!  

[viven44]

My 78 Bronco has a vacuum operated shutoff in AC to turn off coolant flow to the heater core, but it doesn't redirect the coolant, its a dead stop so I always wondered what that means....

The bullnose trucks don't have this feature ???

OBS doesn't apparently... first thing I learned this week about OBS

I also saw on the OBS Facebook page that this is a very common mod, in fact someone recommended this adapter to accomplish this... " people say it's good for another 5 to 10°" ....the one below would redirect coolant flow so I'm considering using the one below on the Bronco...

https://www.amazon.com/dp/B000C2QSVQ/?coliid=IGZP4S810JO0X&colid=3IGQF00LDI4AO&psc=1&ref_=cm_sw_r_cp_ud_lstpd_P7BBT8310K96X74T956M

[ArdWrknTrk]

With Ford trucks the heater core is always bypassing the thermostat, so you don't really get airbound or ever lose heat.
If you see where it taps into the water pump, and the intake bypasses right back, you can understand.

[85lebaront2]

That appears to be a very common Chrysler FWD car heater valve.

[ArdWrknTrk]

I think I'm just going to install a 5/8 barbed ball valve and let the water pump dead head against it.

I'm* a big fan of 'KISS' and everything I see just seems weird and bulky.

[viven44]

Jim, I ordered this today for my Bronco.

https://www.amazon.com/dp/B0989DJLXJ/?coliid=I3F4M217CO34UG&colid=3IGQF00LDI4AO&psc=1&ref_=cm_sw_r_cp_ud_lstpd_66YGSYCEF3ZYJGVR6203

I will see how this manual one works. Needs to be adjusted twice a year... not too bad.

[ArdWrknTrk]

They sell this one -with hose clamps!- for $19.
What's different???

[viven44]

One ships from a "ZHUZHIMAO" for $6.99 and will take 2 weeks to get here and the other from Amazon for free and arrives today.. I'd rather pick the known devil  Truth is I didn't shop... I just picked something and went with it.. as long as it had good reviews.

By the way -- this morning I let the AC turn on immediately so the coolant block off valve was effective from the get go... it made a big improvement in perceived cooling.

I think a manual valve's function may be superior as an automatic vacuum operated valve can temporarily allow coolant flow if someone messed with the controls while driving and filling up the heater core.... but if one was diligent in leaving the AC on all the time that wouldn't be an issue. I don't use the AC much unless I felt uncomfortable so a manual valve would suit me better.

[ArdWrknTrk]

I'm paying more than $7 for 4 stainless hose clamps and I'm in no rush.

While I appreciate immediate gratification I don't necessarily need it.

[viven44]

Well I rushed it, its here... but I am busy and don't have time to get to it until next week  so you did well

[viven44]

Installed it in series with existing factory vacuum operated valve so I can use both depending on how lazy I am in spring/fall

[ArdWrknTrk]

Maybe 3 minutes, and 3oz of coolant.... DONE!