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GMC Safari/Chevy Astro Heating / Cooling



  • cobcob Posts: 210
    It is a vacuum problem. One of the lines that runs from the side of the a/c unit under the hood that goes across the engine maybe the culpret. Does the air only blow out the defrost vents? If so than that is the problem there are many posts with instructions on this forum. Normally if you had a low vacuum problem the air would have worked under acceleration when the engine produces max vacuum pressure and then would not work while coasting when vacuum pressure is lower. Good luck finding the broken line it usually melts on the front of the intake manifold behind the upper radiator hose goose neck.
  • duecekdduecekd Posts: 19
    Hey to all! I have a '92 GMC Safari, bought used, 120xxx mi. When I got it I had the problem of blower only coming out of floor and defroster. I knew it was a vacuum problem because the same thing happened to my '92 Safari which is on its way to it's final resting place. RIP.
    I read in these forums about the vacuum line running from the vacuum ball to the back of the manifold. I checked that line, and it was fine. It had been replaced with
    black "fuel injection" fuel line instead of the very thin plastic line mentioned in previous posts. I had good vacuum at the "tee" connector that goes to the ball, and also goes to a thin black plastic line that disappears into the wire harness bundle and comes out to the "climate control selector switch" connecting to a "Y" connector tube (green in color). No vacuum at that end. To confirm that was the problem, I ran a piece of the same fuel line (with doghouse removed) from the "T" at the ball to the green "Y" in dash.
    Wonderful air began blowing out the face vents again! Yahoo!
    I then snipped off the end of the OEM thin tube at the ball end, and put it in the fuel line. I replaced that end to the "T" and reconnected to the ball. I routed the new hose along the same route as the main wire harness in the engine compartment and drilled a hole just big enough for the fuel line to fit thru in the firewall right next to the cable that opens the hood. (It is located right behind the climate control area in the dash near the doghouse opening) I used another piece of the old thin tube to make a splice to the fuel line and the green "Y" tube. It now works great.

    All that said for the next guy, my new problem is this. When I select ANY setting on the selector switch other than vent, I hear the flaps redirecting air to the right places, but it causes the compressor on the A/C unit to continually click on and off, which also drags the engine down on each ON cycle. It's as if all other positions are now sending a signal to turn on the compressor.
    I know this was long, but any help would be appreciated.
  • reayx5reayx5 Posts: 1
    I have had this A/C & vacuum tubing problem; searched & found this discussion, and with everybody's posts I was able to repair it. I want to thank you guys for sharing the solution, including giving me an idea which vacuum tube to look for. Our temperature high today where I live was 111 degrees, so not only do I thank you, but my family who ride in the van thank you.

  • duecekdduecekd Posts: 19
    I wanted to do a follow up on the solution to my problem for the next guy.

    The problem is stated in the last paragraph of Post #124, so I will not repeat it here. I will restate that this is on a '95 GMC Safari with 4.3L "W" engine.

    I found out that the compressor kicking on and off is due to low freon levels, and there is a low level sensor that cuts off the compressor to keep it from burning up. I had a freon recharge kit that I had bought for my '92 Safari, but never used. It came with 3 cans of 134a freon and a gauge to show freon levels. This gauge hooks to the low pressure side of the A/C system.(Read instructions of similar kits for location of low pressure valve in your vehicle).

    The gauge would jump up and down with the cycling of the compressor, so I was unable to get a steady reading (This is with the engine running and the A/C on Max)

    I found out that if you remove the connector for the low pressure sensor, which on my van was located on the back side of the accumulator(a silver cylinder a little bigger than a soda can on front passenger side of engine compartment at about 11 o'clock.),also the same place my low side fitting was located, at about 5 o'clock.

    Remove this connector an short between the 2 female pins of the connector (I used a paper clip bent into a horseshoe shape) This will keep the compressor running all the time.
    The gauge now clearly showed that the freon was low. I added 1-1/2 cans (approx 18oz) of freon, and VIOLA, COLD air. It has been about 3 days now and still OK. I will check in about a week and see if the gauge still reads good, or if I still have a leak. The kit I bought had 134a refrigerant,oil and a leak stopper built in. Hopefully it works!!

    Hope this helps some other HOT person down the road!
    Good Luck!
  • my van had vacuum problems. I replaced the lines and now the ac controls work except when accelerating. When I accelerate the air goes back to the defrost vents. Upon taking my foot off of the gas the air returns to the selected vents.

    Please help
  • duecekdduecekd Posts: 19
    I am not a mechanic, but I stayed in a Holiday Inn Express last night! My guess is you still have a vacuum leak at either the "T" connector that goes to the vacuum ball, or the vacuum ball itself is cracked or the line is not connected to it. From what I understand, that vacuum ball is made to hold enough vacuum to compensate for changes in the engine speed, and keep the vacuum at a constant. The only other thing I can think of is that one of the lines is getting pinched somewhere during acceleration and torque of the motor.

    These are just guesses, If I've stated something incorrectly, someone with more expertise please straighten me out. Good Luck!
  • Thanks for the advice, I tend to agree with you. I have a limmited knowlege of the vacuum system so I sure could use a vacuum diagram. I have checked several manuals, hayes, chilton, and nothing. All the lines were replaced by the mecanic with rubber tubing but it was doing thison acceleration once I repaired the first break. The mecanic did replace the origional T with a different kind, one with out the round thingee on one side. That darn ball is just so hard to get at, thanks chevy.
    Gotta love these American vehicles and their magicly disintegrating rubber and plastic. Everythin made out of plastic under the hood is super brittle now and is starting to break off in little pieces everytime I lean on or touch it. I will recheck the vacuum lines and try to reach the ball somehow. Thanks again I appreciate your post,

  • nedrnnedrn Posts: 1
    When I turn the climate settings to off and turn off the engine the blower motor stays running on high. Even when the engine is on, the fan only stays on high. The purple wire that plugs into the back of the switch in the dash does not have electricity running through it when unplugged from the switch and the fan continues to run. Do you think it is a vacuum issue or relay / voltage regulator issue?
  • duecekdduecekd Posts: 19
    I have never had the exact problem you are describing, but I will throw this out there as a possible cause. I believe your blower relay is stuck, or fused closed. On my '92 Safari, I had what I think is your problem in reverse. My blower wouldn't work only on the high setting. It turned out to be the blower relay, which on my van was located on the firewall right above the A/C unit on the passenger side of the engine compartment. There are 2 small silver relay cans a little bigger than a Zippo lighter, and on my van, the blower relay was the one on the left. Remove the screw holding it to the firewall and unplug the wire harness from the bottom. You should be able to get a replacement from any parts store. I would take it in with you so they can match it up. The one I got didn't look identical, but plugged right in and worked fine. Good Luck, and hope this helped!
  • I just found this forum and it helped me with my 2000 Astro a/c problem, air blowing through the defroster. I found the vacuum hose, which was breaking into pieces, and replaced it. Thanks to everyone for the great information and easy to follow repair instructions.
  • I need to know the location of the rheostat for a 96 safari. Front fan won't go to high and rear heater fan won't work at all, but ac fan rear works fine. Purchased a new rheostat. Where is it? On the firewall side?
  • My safari front fan works for low and med, but not high. Is this the blower motor rheostat possibly? I have checked all fuses.

    Also, the rear heat wont come on at all.
  • There is a resistor network on the front side of the blower housing. This is under the hood, on the passenger side. You will have to remove the coolant bottle to get to it. You will probably find that not only is the resistor network damaged, but the harness plug also needs to be replaced. Ay least that was the case with my '97 Safari.
  • I have a 98 safari that has been giving me problems with the heater. I have an hour commute to work and the heater never gets even a little warm! At first I could pull over and let it sit for a second , then start it back up and it would work. Then it got to where it just wouldn't work except for every once in a while out of nowhere. What could this be? Thermostat stuck open? I have made sure is full of antifreeze/water. Where should I start?
  • I have found this forum very helpful. I am having a problem with the vent controls in my 2000 Astro. It only blows out the defrost and the passenger side at the bottom. I found that one of the small vacuum lines (the one that runs to the manifold) was brittle and leaking, so I replaced it (had to remove the doghouse though :cry: . Its a pretty common problem that is well documented on this forum. But my vent controls still don't work. The new line has plenty of suction now and had to be replaced but the problem remains. Any ideas?
  • Try checking out my post #124, first part in this same forum. I think you'll find you don't have vacuum at the hose end to the selector switch. Hope that's it.

    good luck, it's getting to damn cold to be messing with no heat!!!
  • i just bought a 1996 astro,the seller told me that the heat wasnt working, so i new i had something to fix.i had to replace the water pump,it was leaking.i also changed the therostat,heater resister,fixed the vacum leak from ac to the manifold,checked the heater core and still no heat.all the control setting seem to be working,every time i turn on any setting cold air blows out.i think it might be the door that the outside air comes in isnt closing,any advice to help would be very welcome.also where is that door?
  • Hi; I'm Curt and I have the same problem. Did You ever find a diagram? and if so where is it?
  • My rear fan works fine, but always cold. I checked the vacuum lines in the engine comp. that control the valve that lets hot water go to the rear heater. If the rear heater core was clogged, would both lines be cold, or would the input be hot and then the return cold? Seems if the core was plugged, no water would move anywhere. And how can you test the valve? It seems fine, all hoses connected, etc. Anyone ever have a core plug? I haven't...thanks
  • I am having same problem with my Chevy Astro '97. I have flushed coolant, replaced thermostat, I think it may be the water pump - although the standard tests for this seem to indicate that it works. My car never over heats, and the gauge indicates that the car generally operates in the 150 degree range. The thermostat is set for 195 degrees. The gauge goes up to 210 and slightly above, then drops suddenly down to the 150 - 170 range. I have checked the lines to and from the heater core, and liquid is flowing through it. The lower hose (in to the heater core) gets warm, but the upper is cold. I just drove cross country, and the heat worked intermittently (mostly it just didn't work). The temperature outside has been cold (in the teens), and the heater works more often when it is a little warmer (40's and above).
    If anyone has found a solution, I would be very interested to hear it.
  • i had the same problem,follow the hoses from the heater core to where they meet vat a temp.control valve.what the valve does is it opens to let coolant flow to the core.check and see if it is stuck,there is a little plundger in there that you see the top of it to see if it as moving in or out.if it is working fine the tryt flushing the core,thats really easy,just disconnect the hoses to the core in the engine compartment between the ac and the pass fender.take a hose and hold it on one tube and then the other.its a little messy.dont forget that when you fill it back up with anti freeze run it for a while to let the core fill back will need to top off the radiater
  • I wrote a few posts ago about the vacuum problem in my 2000 Astro. That problem is now fixed but now (1 month later) there is a new problem. When I put my foot on the gas, the air stops blowing from the vents and goes back to the passenger side bottom and defrost only. If I take my foot off the gas, it will start blowing out the vents again. Whats more is that the rear heat turns cold with my foot on the gas and goes back to warm when I take it off. This is a weird car.
  • The control valve is up in the engine compartment attached to the AC Evaporator housing, isn't it? I found mine, but cannot figure out if it is faulty. I did have issues with my rear heat low/med/high switch, and it seems to have failed. I did get it pulled apart and found a way to jumper 2 pins so I can get the rear blower to run on high, but have only cold air-because the water line is cold. So, I assume that the plunger unit is faulty, as my front heat is fine, and new radiator etc...You said to disconn the hoses betw the ac and pass. fender. could you email me at [email protected] so you could walk me thru this? Thanks
  • Hi folks, been finding some great info in the forum, but still can't get any heat. I pulled out the doghouse, and sure enough found a rotted vacuum line. It ran from a T on top of the engine down to another T on the pass. side. That T went into a connector on the
    fender wall and a skinny plastic line that went into a wire bundle. I replaced that line, but it didn't help. Any other ideas?
  • duecekdduecekd Posts: 19
    anim8r21, you said you can't get any heat, but does that mean the blower isn't blowing heat, or the heat is coming out of the wrong vents or what? You said you replaced a vacuum line, which one? The one from the engine to the vacuum ball canister, or the one that goes into the wire bundle to the selector switch on the dash?

    Need more info on whether you have a possible stuck thermostat, and no heat, or your blower isn't blowing the heat thru the right vents, or the blower doesn't blow at all?
    Would love to help, it's too damn cold!! (Even though we went from the teens last week, to 73 today. I actually rode my Harley all day yesterday with just a jacket. That's St. Louis weather for ya!!)
  • you could take off the air filter housing,it should pop right off then you can look down at the plunger and see if it moves in or out.i took a long screw driver and kind of pulled up on the metal linkage on the top of it.if it moves up when you pull up on it you should replace it, also check the vacuum line that connects with the valve,.you should have someone start the van while you watch the top of the plunger with a flash light.if it is moving in and out when you turn the heat on and off it is working properly. as for the core,just unhook the 2 hoses and hold a garden hose to the core tube,top or bottom first,it doesn't make a difference.the water should flow through and back out the other tube at a good flow.if it piddles out or don't come out at all then its plugged.i didn't know much about these vans until i bought one.i had no heat and high speed on the fan.i asked my buddy who is a mechanic,he helped me trouble shoot the i have heat on all speeds I also had the airflow mixture door stuck open so i was always sucking cold outside air in through the core so it wouldn't get hot just slightly warm.feel free to ask me anymore questions,i don't mind,its how i got my info.
  • Im so unhappy. 96 Safari. Simultaneous failure of rear heat switch (would not work at all) and front fan only working on speed 1,2, not 3. So I ripped out the rear heat switch and fiddled endlessly with it-nothing. Finally jumpered the 2nd from the bottom pin on the left to the right bottom pin and the rear fan comes on high finally, but always cool. 1) where is the $#^&@^ airflow mixture door. 2) you see a plunger after you take off the air filter housing? *$*#*@ I see bolted to the a/c evap housing on the pass side engine comp.what I think is the heater control module where the hoses come into. Both lines are cold by the way...3) the resister in front is toast I think becaues the red wire connectn seems burned. Guy checked the board and thinks its toast. For the front then, I believe I need a new resiister, but I did check it and current is going thru the red conn. And the aftermarket(and even dealer)resister won't fit into the hole-it has 4 plastic pins on it and it bumps the plastic housing. &$*$&#* GM, why can't they make it easier... #((#@( sick of this. Please reply asap. thanks :sick:
  • I am so angry at parts mfgr's. The front blower resister controls the fan speed for the front of my 96 Safari. The one that is in there is damaged, and so I took it out, and bought a new one. The new one has 4 plastic pins at each corner kind of 'protecting' the circuit board? Idiots. With those pins there the new resister won't fit. Do I bust them off? Freeking morons.

    Also, if anyone knows how to test if the rear heat control valve is working, let me know. I believe I found it on the pass side in the engine compart. bolted to the AC Evap housing, but cannot tell if its not working. Is a plunger visible? Can I push or pull it? I am just so sick of no heat. :sick:
  • Basically, I have no heat at all from any vent. The fan blows, and when I push the selector to hot, it is less cold than when the selector is on cold, but not much difference. The engine runs at a normal operating temperature. The vacuum line I replaced runs from a T junction on top of the engine, down to another T junction by the passenger fender well. The T by the fender well has a short piece of hose that connects to a nipple mounted into the fender well, and then a skinny plastic hose runs into a wire bundle next to the radiator. Where is the vacuum ball canister?
    Dallas weather is pretty crazy too, we go from low 30s to high 70s in the course of a couple of days! Wish I had my Gold Wing running! Know much about [non-permissible content removed] carbs? :-)

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