Jaded Posted August 17 Share Posted August 17 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... Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 17 Share Posted August 17 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. Link to comment Share on other sites More sharing options...
Jaded Posted August 17 Author Share Posted August 17 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. 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. Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 17 Share Posted August 17 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. 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. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 18 Share Posted August 18 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. 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.... Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 18 Share Posted August 18 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.... 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. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 18 Share Posted August 18 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. 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? Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 18 Share Posted August 18 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? 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. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 18 Share Posted August 18 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. Right away Captain! Link to comment Share on other sites More sharing options...
viven44 Posted August 18 Share Posted August 18 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. 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 Link to comment Share on other sites More sharing options...
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