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GMC Safari/Chevy Astro Heating / Cooling



  • please send pic of vacuum line fix,thank you
  • 97riv97riv Posts: 4
    Have read the forum on Safari heat and cool problems. My problem is after starting the the van it throws heat when the temp. gauge is half way up to normal operating temp.Once it warms up to normal operating temp. the air goes luke warm and sometime cool,and once in a while it will throw hot air. It is hit and miss but normally it is cool air.I am going to change the thermostat today and see if that works.I have owned 3 of these vans and never had this problem ,just the rotted vaccuum which is common with these vans.Very good forum!
    Any ideas on this problem. I will post tommorrow about the thermostat change to tell if it was the problem. :confuse:
  • 97riv97riv Posts: 4
    It wasn't the thermostat? I tore everything I could apart, the heater lines are hot ,the damper door on the passenger side stays shut till you put it on A/C then it opens.The vaccuum actuated mixing valve seems to work O.K as the arm goes up on full heat position and down on cold position.Every morning I start the van and it clears the windshield (we have frost here now ) the temp. gauge goes quqrter qway up then it stars to blow cool air? Could it be the heater control resister heats up and goes to cold? I'm stumped.
  • tstormtstorm Posts: 10
    Are you sure the coolant level is full?
  • 97riv97riv Posts: 4
    :lemon: The coolant level is good.I found out my rear heat works fine, as I use it for a work van and don't use the rear heater,but have been lately to keep he van half warm.As I said before, lots of heat at the front till the temp. gauge goes to around 1/4 on the scale, then I can hear the blower speed up and the cool-to cold to luke warm air starts.When it first starts this it will cycle hot cool for a bit then just cool air. I'm sure it is the control that heats up and it is like turning it to cold, as it opens a damper to let the cold air in, I just don't know wher this damper door is?I know there is one by the passenger side where the heater core cover is but don't believe that is the one? Soon as E-Bay has the right control (rear defrost) at a reasonable price I will purchase one and try it.
  • gss56gss56 Posts: 1
    Could you send me a copy of the vacuum hose diagram. I'm having that exact same problem with my 98 Astro Van. Thanks!
  • bdar,

    Can I get a copy of that vacuum diagram?

    My e-mail is
  • Thanks for the info. Please email me the diagram as I have just started to have this problem.
  • Hey, I have this exact same problem and I found the broken vac hose. I just need the diagram to run a new one, could you please e-mail it to me at thanks a lot
  • please send the diagram to

    thank you, we've had this problem for way too long. it will be great to get it fixed.
  • please please forward that diagram to me as well or maybe post a link to it on here....we have looked all over and can not find this diagram ANYWHERE!!!

    I would really appreciate it!
  • 97riv97riv Posts: 4
    Post # 213 has the vacuum diagram.The vacuum line that usually needs relacing is a small line about 1/8" and runs from behind the accumulator (silver can) on the passenger side to the motor behind the A/C condensor.It's hard to change without removing the engine cover but can be done as I did mine 2 months ago.
  • Not sure if you got it fixed yet but the most common problem with the fan motor is either the fan itself or, most likely the governor's located on the heater box under the hood. Has a plug going into it right next to the blower fan. The coils corrode and break...These are your speed condensers..:)
  • It still is not working on the high speed. Hasn't for a couple of years now but only on the first two settings. Is this the type of problem that could easily be fixed by replacing the govenor switch? Is it something that one can install or change easily with little mechanical knowledge? Thanks everyone for much information about the various problems with the heater contorols.
  • Had this problem on a '92 GMC Safari. It is most likely the high speed fan relay located on the firewall above the fan box on the far left side of the engine compartment looking at the firewall. There are 2 relays there, and I don't remember which one, but if you trace wire harness on plug, it should lead to the fan motor. You can get this part at any parts store or the dealer for fairly cheap. The replacement may not be exactly the same shape, but it will work fine. Just make sure its attached to the firewall or the frame for a ground. Good Luck, it's too damn cold not to have "HIGH"!!
  • Heat from vents blows luke warm or cool air. When van idles or I come to a stop, air blows cool. When I accelerate, air becomes luke warm but not hot. When there is stress on the engine going uphill, air sometimes stops blowing from vents, but when I remove my foot from the accelerator, the air comes back, but still luke warm or cool air.
    Replaced radiator, new radiator cap, new radiator fluid, replaced thermostat, replaced heater core, replaced water pump, mechanic checked all vaccumn lines and performed smoke test on vaccumn lines to check for leaks, replaced T where vaccumn hoses connect and a few other minor parts, but still the same problem. Mechanic says he doesn't know what else to do.
    I getting tired of taking the van back & forth to the mechanic with no results. Currently 228,000 miles. Can anyone solve my problem?
  • 8poncho8poncho Posts: 1
    2005 Astro, read many of your blogs, looked at the diagram, opened the hood and patched the hose in 5 minutes. Thanks, if I could buy you lunch, I would.
  • I am having the same problem with my vents not switching, its stuck in the defroster position. I will try your written instructions but if you could please send me the diagram of the vacuum system.
    God Bless,
    Sincerely, Mike Evangelista
  • i have a 98 astro and i took many of the inside panels out for shelving on mine the rear heater core is right behind the driver seat and i think the panel just pops out. i have not tried to take mine out but i did have a mechanic recomend just bypassing the rear heat since mine doesnt work anyway.
    but ussually its not that hard to get them out sometimes its a pain if you have to take the hole dash apart
  • yea mine did the same thing it was bad i had a small crack on my windsheild and it cracked all the way across cause i couldnt change it turned out the vacumm line was right under the hood on the passenger side up by the firewall
  • jockohjockoh Posts: 3
    could you please explain how to do this, where do you cut and what do you do after you cut,and how do you fill the hole that will be left after the job is done thank you for your time
  • jockohjockoh Posts: 3
    If you still have that diagram for the vac hose could you please send it to me via email
  • jockohjockoh Posts: 3
    please send to
  • scottcb1scottcb1 Posts: 4
    I don't know if you still reading threads on edmonds, but I am having similar problems with my 96 astro awd with rear a/c heat installed. I am losing freon fast, [about 1 hour and presure gone after putting some in] I can't hear it leak out but it has to be a BIG leak somewhere. Just want to ask someone before I try tracing this down and dissasembling VAN all the way to rear of vehicle. Any shortcuts, advice, suggestions would be great.

  • billiam3billiam3 Posts: 1
    That is great you found the diagram! Could you please send it to me?
  • scottcb1scottcb1 Posts: 4
    That is great you found the diagram! Could you please send it to me too?
  • voxon4voxon4 Posts: 2
    Please send me a diagram , have a nice weekend.
  • i was wonderin if you might be able to help me. i own a 96 chevy astro 2 wheel drive 4.3 liter . my vacuum lines are a mess and the ac blows fine in the rear but only comes out of the defroster. i dont think its a switch but something isnt getting enough vacuum to open . ive looked under the doghouse and the line is secured to the top of the engine , it goes across the top of the engine over the alternator and just stops, i can hear vacuum but i cant figure out where this hose goes.i live in the high desert and it gets 110 degrees in the summer. so air would be great. please help me thank you
  • scottcb1scottcb1 Posts: 4
    I would like to help you out but I don't have a clue. I asked several people on this board for vacuum diagrams that are floating around, but no one ever responded to me. perhaps you will have better luck than I did. If you do get this diagram would you send me a copy of it, it sure would help.

  • geraldlgeraldl Posts: 3
    I believe you may be correct when you are guessing vacuum problem. However, I have no solution. Please note that if the AC has the correct amount of Freon, the AC will kick on and off frequently. When the AC stays on forever, it typically means there is not enough freon. The only remedy I can think of is to let a mechanic test the vacuum lines. If you have the time, check for old/cracked/dried vacuum lines/hoses. Especially where the lines connect. If dried/cracked, replace the vacuum lines/hoses. Also make sure the fitting of the hoses are not loose. Good luck.
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