How JustAnswer Works:

  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.

Ask Randall C Your Own Question

Randall C
Randall C, ASE Master Tech
Category: Chevy
Satisfied Customers: 11084
Experience:  ASE Master, L1, 32 years, Diagnostic / Electrical Specialist
Type Your Chevy Question Here...
Randall C is online now
A new question is answered every 9 seconds

Where does the vacuum hose on the heater control valve connect

Resolved Question:

Where does the vacuum hose on the heater control valve connect to on a 1997 Suburban 2500 4WD 454 engine with rear AC?
Submitted: 3 years ago.
Category: Chevy
Expert:  Randall C replied 3 years ago.
Hello, how long of hose end do you have? what end is undone?
Customer: replied 3 years ago.
I replaced the heater control valve because the old one broke. The vacuum hose attached to the old valve was disintegrated and the end away from the valve wasn't attached to anything, so I don't know where it goes.

There is a small cylinder (roughly 3/4" diameter and 1.5" long) attached to the firewall above where the coolant lines go thru the firewall. It has an electric plug and 2 small hose barbs on it. From what I read elsewhere, it sounds like that might be what applies the vacuum to turn on the heater control valve. I'm guessing that it electrically opens a valve that allows vacuum from the engine to be applied to the heater control valve. But if that is the case, then there is another vacuum hose missing on the second barb fitting on that cylinder, and I need to know where that goes, and whether the hose to the heater control valve attaches to the top or bottom fitting on the cylinder, or whether it works either way.
Expert:  Randall C replied 3 years ago.
Thanks. yes, the hose from valve to solenoid goes on botton fitting. the problem is i can not lcoate anywhere a pic of where the other hose goes to/from. i will say, the line to the top fitting is to be MANIFOLD vacuum so it goes to engine directly on or near throttle body OR look at rear of engine near the fiel pressure regulator that has manifold vacuum as well . There may? be a "T" fitting there, look at the underhood vacuum diagram label which shouild be on or near on top of radiator? they put the label in different spots. the valve is not very important at all. It only turns off water to heater core to help AC cool a little better in very hot weather. I understand you want done correct but.. I just do not remember nor pictures to show where other line hooks up. I would look around back of engine etc as you may find the balck/hardplastic line laying somewhere. If not. look close at throttle ody for empty vac fitting and look near fule regualtpor as well for fitting. if all else fails, get a vacuum T from parts store and insert inline to the Fule pressure regualor hose. It will do exact same thing. the top fitting is to be full vacuum when engine at idle



graphic
Customer: replied 3 years ago.
Thanks for your answer. That certainly answers the first part. As to where the vacuum hose from the solenoid goes, I did not find any fittings or hoses around the throttle body. There is a small, black, hard plastic hose that goes across the top of the engine. It is unattached on the passenger side, and broken off on the driver's side. I can't find where it might attach on the driver's side. Any ideas?

There is a slightly larger hard plastic hose going from the large black cannister behind the left edge of the radiator over to a square thing with an electric plug sticking out of the intake air manifold on the driver's side. Is that the vacuum line to the fuel regulator? Tapping into that would require a tee where the leg of the tee is a smaller size.

Here in Tucson, we do have very hot temperatures, and a Suburban has a very large interior volume to cool.
Expert:  Randall C replied 3 years ago.
Did you look at under hood label? I will be the smaller vacuum line One end goes to solenoid, other, you have to find a fitting or T that may have broken off on one end. i wish i could give moe info but just can not remmeber without looking.
Customer: replied 3 years ago.
The label is on the air filter housing. It indirectly led me to an empty rubber elbow coming out of the air intake manifold, which has suction on it. When I connect that directly to the heater control valve, the valve activates. When I connect it to the solenoid, it doesn't, so there is an electrical problem. But I already knew that there are electrical problems with the AC, because I have to bypass the AC relay with a jumper wire for it to turn on. I guess I could leave the vacuum line attached directly during the summer, and connect it to the solenoid during the winter.

Thanks for your prompt help. I will click "Accept" after I send this.
Expert:  Randall C replied 3 years ago.
yes, sounds like electricl problem maybe at conttrol head etc. Glad you found the vac source. Yes.. it is to have fulltime vacuum like you describe. soory you had to search some but info is very limited due to age
Expert:  Randall C replied 3 years ago.
here is a diagram for reference. the HVAC control module may very well be your underlying problem. Idoes control compresor funcyions as well as heater control valve. it is a micro processor

graphic
Randall C, ASE Master Tech
Category: Chevy
Satisfied Customers: 11084
Experience: ASE Master, L1, 32 years, Diagnostic / Electrical Specialist
Randall C and 4 other Chevy Specialists are ready to help you

JustAnswer in the News:

 
 
 
Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.
 
 
 

What Customers are Saying:

 
 
 
  • I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money. Todd L Rochester NY
< Last | Next >
  • I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money. Todd L Rochester NY
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex Los Angeles, CA
  • Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult. GP Hesperia, CA
  • I couldn't be more satisfied! This is the site I will always come to when I need a second opinion. Justin Kernersville, NC
  • Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around. Esther Woodstock, NY
  • Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know. Robin Elkton, Maryland
 
 
 

Meet The Experts:

 
 
 
  • Tim's Auto Repair

    mechanic

    Satisfied Customers:

    7641
    Have owned a repair shop for 25 yrs.
< Last | Next >
  • http://ww2.justanswer.com/uploads/TI/tim37857/2011-10-28_23053_S6301814.64x64.JPG Tim's Auto Repair's Avatar

    Tim's Auto Repair

    mechanic

    Satisfied Customers:

    7641
    Have owned a repair shop for 25 yrs.
  • http://ww2.justanswer.com/uploads/DT/dt69nova/2012-6-15_234154_pic1.64x64.jpg Dave Nova's Avatar

    Dave Nova

    Chevrolet Technician

    Satisfied Customers:

    6870
    ASE Master Certification. GM World Class Certification
  • http://ww2.justanswer.com/uploads/ggrote1/2009-06-27_031011_me.jpg Gary's Avatar

    Gary

    Chevy Technician

    Satisfied Customers:

    5404
    15 years GM master tech
  • http://ww2.justanswer.com/uploads/testedtuff/2009-09-26_170108_pictures.jpg John's Avatar

    John

    Master A.S.E Automotive technician

    Satisfied Customers:

    4071
    A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
  • http://ww2.justanswer.com/uploads/RO/rodcuda/2011-7-25_224114_Donhoff1.64x64.JPG Neal's Avatar

    Neal

    Chevy Mechanic

    Satisfied Customers:

    2306
    Shop Owner and Mechanic on multiple makes.
  • http://ww2.justanswer.com/uploads/goodwrench9124/2008-11-09_220838_dscf0007.jpg goodwrench9124's Avatar

    goodwrench9124

    ASE Certified Technician

    Satisfied Customers:

    2041
    Ase Master Certified, GM Master Certified Tech. Awarded GM Top performer, Hybrid certified
  • http://ww2.justanswer.com/uploads/DR/drivefast1971/2012-1-12_172422_0009051tQKh.64x64.jpg Ron Z.'s Avatar

    Ron Z.

    - Chevy Tech -

    Satisfied Customers:

    1912
    18+yrs experience. State Inspector and Chevy Diagnostics