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GMC Safari/Chevy Astro Heating / Cooling



  • Yesterday I noticed a small amount of heat coming from the lower vents. There is plenty of airflow from all other outlets.
  • I need to replace my front heater core on my 99 Astro.
    The factory service manual says to remove the access panel.
    But there are no pictures/diagrams for the heat core removal.
    My assumption, is that it can be removed from inside the van on the passenger side as the heater hoses go through the fire wall.
    Am I correct?
    Any assitance in removal/replacement would be appreciated.

  • I have a good tip for those of you who have the same problem I did.

    First off, thanks to all of you for helping me diagnose the problem. I went the doghouse route, by the way. Yes it was a pain, but I think it would have been worse to try and do it through the hood. The break in my line was about five inches off the connection at the intake. From the hood side, it looked as though someone had already done this before because there wasnt't the thin factory line or the thicker elbow at the tee end; there was just what looked like a typical vacuum hose (maybe 1/4 or 5/16 inch).

    Anyway, the line was connected at the tee and just dangling down toward the Vacuum Ball (or whatever you call it). I pulled on it and it came up free (unconnected), so I just assumed that it was disconnected at the Ball. I spent a good hour under the car feeling around the ball, but all the lines were connected there. The unconnected end of my 1/4" line (again, remember it was connected at the tee near the evaporator), had the 1/8 inch "stiffer" line sticking out of the end, oh about an inch and a half. After reading some of these threads I found that this was indeed the line that goes back to the intake and at that point, the elbow was intact and there was about 5 inches of pretty stable 1/8" line.

    So I went to the auto parts store. Of course they didn't have the dealer part, so I started looking around for some tubing. The guy had some 1/8" nylon tubing, so I got a 72" spool of that for $5.95. I also got some bigger tubing for which I hoped the inch or so of protruding 1/8" line would go into. If not that, then maybe the nylon tubing would work. The bigger line that I bought had a 7/64" ID, which I though would create a nice snug fit. It didn't. The 1/8" nylon tubing was too loose and slid around too easily in the larger tubing. Which made me think that the dealer 1/8" tubing is really for ID not OD. And of course the 1/8" line that was protruding from my unconnected line just fell apart when I tried sticking it in the new 7/64" tube.

    But not to despair. My 7/64" ID tubing fit pretty well on the factory 1/8" line coming out of the intake. (oh yeah, I paid a whopping 79 cents for a foot of the 7/64" tubing). But I still needed to connect that to the line that was coming off the tee and, as I said the 1/8" protrusion was crumbling. This called for a splice. If the nylon tubing hadn't been so small, I could have used it. But like I said, it was just too loose. So I started thinking: What would be about that size; I only need a section of it to connect the two larger tubes.

    Hey, what about one of those extension wands that are on a can of compressed air or WD-40? No good. Too small. And then I had my brainstorm: the ink tube in a cheap ball point pen. It took about five pens to find one that was almost out of ink (I wanted it clean and as much as I could get), but it was a perfect fit.

    Turns out I could have gotten away with just a couple inches. But the bottom line is that with a piece of ink tubing from a cheap Bic pen (which are about $1.00 a dozen, so less than 20 cents for the one pen which had pretty much already served it's purpose anyway) and a 79 cent one foot piece of 7/64" ID tubing, I got the job done, with plenty of extra space to route it over the air cleaner housing.

    All climate control vent settings now work like they're supposed to. Thanks to you guys and about a buck.
  • I have read several posts on heater fan speeds, but I still am not sure what my problem is. On my '97 Astro van I have a four speed fan switch, but only get the two higher speeds to work. The fan is off in the first two settings. I have replaced the blower, but still have the same problem. In other postings a relay has been mentioned and also a resister pack. If this might be my problem, where are both located and which is likely the culprit?
  • My 2003 Astro's heater motor is almost dead. Started making ugly grinding noises and will only run if i hit the fan housing a few times. I want to replace the motor myself but am not sure how to even remove it. How do you access the motor? Thanks in advance.
  • Most likely it is the resistor pack. It is on the blower housing under the hood. You have to remove the coolant overflow and washer fluid bottles to get to it. It is directly behind them. Also look at the condition of the plug on the wiring harness. I had the opposite problem as you, all speeds EXCEPT High worked. That "pin" on the harness was fried. I had to get a replacement at a salvage yard.

    The relay is a part of the resistor pack.
  • bbri67bbri67 Posts: 3
    Just replaced the resistor for the blower due to a failure.Blower works fine now,but heat seems week.All the vacuum lines seem fine,all the vents open and close right.All fan speeds work and the heater core is heating up great.I just can't get the good heat to come out unless the controls are set to max a/c.On any other setting the heat is coming out but it seems to be luke warm not hot.And to top it off the temps here in Chicago are finally dropping.Any ideas?Thanks.
  • cobcob Posts: 210
    The reason that the heat works better on Max A/C is because it is recirculating interior air and not mixing in fresh air from the outside like the normal vent/AC/heat settings. Is your thermostat working properly? Mine runs at the mark directly between 100 and 210 which I figure to be around 160 but I installed a 180 thermostat instead of the stock 195 to keep it cooler in summer for towing. You may also want to check your coolent level, these engines are prone to leaking intake gaskets and coolent goes in the oil or on the ground depending on where the gaskets fail. On these cold days in Michigan I can drive 10 miles on the highway at 75 MPH before my thermostat opens for the first time. It takes a while for the van to warmup compared to other vehicles I have owned but can't beat the AWD in the snow.
  • bbri67bbri67 Posts: 3
    I just replaced the thermostat with the 195,and replced the anti-freeze with a good 50/50 mix.I found a heat control valve in-line with the heater core that didn't have any vacuum going to it,but like I said the heater core is getting good and hot and the vents will only blow luke warm air.The engine temp runs about the same as yours(which I thought was a little low but I guess not).Maybe It's working sluggish due to the cold temps.I'm not sure because it's my wifes van and I never drive it.Thanks for the reply I'll keep digging around.It's probebly going to end up being one of those crappy vacuum hoses buried somewhere.Thanks again.
  • bbri67bbri67 Posts: 3
    Turned out to be a flapper that mixes outside air with the hot.Wasn't closing all the way,a slight reallignment and its back to normal.Of course I had to dig deep to get to it. I'm getting pretty good at rippin that dash apart though.
  • dtreetdtreet Posts: 5
    I seem to get very little heat from the lower vents. It appears that hat air is trying to exit from the defrost shen I have it on floor only.
  • cobcob Posts: 210
    Broken vacuum line, see posts 25-40 for explaination of how to find and replace.
  • dtreetdtreet Posts: 5
    Thank you for the help!
    My feet have been cold this winter with the chilly tempertures we have been having here in Colorado.
    There is plenty of air blowing from the dash vents so at least my fingers stay warm.
    Is this vacum hose controling all of the settings? Everything else seems fine except for the floor vents.
    Has anyone found the hose in bulk sincelast summer?
    Any clues on a gas gauge that will vibrate, drop to emopty and then raise all the way to above full again?
    Thanks again!!
  • cobcob Posts: 210
    The vacuum controls all the settings and the default setting when there is a vacuum loss is to the defrost setting so air only comes out the front window defrost vents. Someone else in an earlier post found that a flapper in the system was not closing so they did not get hot air at the floor only cool air but they got hot air in the A/C max mode.

    Fuel gauge problems are ususally linked to the sending unit which I believe is in the tank with the fuel pump assembly. Someone can correct me if I'm wrong. At some point your fuel pump is going to go out on you, it is another free option that GM builds into all their trucks. At that time have the sending unit replaced also unless there is another fix for your gauge.
  • jodivanjodivan Posts: 11
    wonder if all these prob are typical of other Safari's since we road tested a 2000 (cause we need the 8 seats) and noticed cold coming out of rear heat, and other minor things, but did seem to drive ok. Should we just try to find something else with 8 seats? wish we could get past repair list, but it was sold by flint auction to used car dealer. :confuse: jodivan
  • probly bad hoses I had same problem
  • I have 1992 gmc safari. hot air comes out defroster but window stays fogged. note: It looks like there is water coming in through top of window.Would that cause the fogged window?
  • You people are aright!
    My 2001 GMC Safari also had no heat from some outlets.Sometimes they would finally open up.You told me where to look for that tiny plastic vacuum line by the AC unit and where to look on the intake manifold. Sure enough the line was brittle and leaking by the engine.Nappa Auto sells 3' lengths of the plastic tubing(1/8")and the old fittings just pull out.I did cover the engine end of the tubing with larger rubber tubing too.and routed it over top by the air cleaner.
    Hardest part was getting the doghouse off.
    Total repair cost $4.00
    Thank you ;)
  • I bought my 97 Astro new and now am having trouble with heating. I sometimes have cold air coming out of the front vents, sometimes luke warm. I have heat coming out the factory rear. Sometimes this changes, and I get cold air out of the rear and luke warm air out of the front. My selector directs the air flow to defrost, bilevel or floor fine. My antifreeze is full. I have no leaks. I replaced all of the 5/32 vacuum lines from the ball under the antifreeze res. and to and from the control valve. I have read all of the threads prior to mine and am wondering if anyone has had to replace the heater control valve behind the silver air conditioner tank on the pass. side under the hood. Mine has two vacuum line attached with an electrical solinoid on top and heater hoses on the bottom ports. Also, what is the function of the 1/8" black vacuum line which goes across the top of the motor. It looked like it was ok but didn't take off the dog house to inspect the whole line. I know that my thermostat needs changing because it only gets to about 150 degrees. But, would this cause my eratic heating in front and back? Seems like it could be the heater control valve to me but not sure. Thanks to whomever can help!
  • cobcob Posts: 210
    First, replace the thermostat, takes 10 minutes no gasket no permatex the thermostat has a rubber gasket around it simple fix. That maybe all it takes to get the heater to work, start with the simple fix. The 1/8" line is the one that usually fails. It is the line that goes to the vacuum port on the intake manifold and creates the vacuum for the system. When it breaks your heater defaults to the defrost setting and based on your post you have no problem with that at this time.
  • Cob, sounds like good advice. I already have the thermostat and gasket so I'll replace it. Do I need to drain all of the antifreeze out of the radiator? I can't find a petcock on the lower radiator to drain the antifreeze. Do you unhook the lower radiator hose to drain it? Or do you just pull the hose from the thermostat housing and loose what is in the upper hose? Thanks again.
  • cobcob Posts: 210
    If the van is cold than the fluid in the upper hose will mostly be drained down. There is no petcock so just remove the upper hose and when you remove the goose neck you will lose maybe a quart at most of fluid after all this is the highest point in the cooling system and when it is not under pressure it should drain down to the lower level.
  • Thankyou Mr.Cob, I will change the thermostat tomorrow.
  • My experience in repairing my 98 Astro vacuum hose problem was almost identical to tkw! Including holding the rubber fitting between my left index finger and middle finger and feeling stuck there. After some patient twisting and pulling, I was successful in pulling the fitting from the manifold end. The vacuum hose was extremely brittle and broke into pieces very easily. Project completed all from under the hood!

    My creative fix was to remove the small original tubing from the rubber fittings at each end and used 1/8" drip irrigation tubing (which I had plenty of) to push into each rubber end fitting, re-route over the air filter away from extreme heat and...success. Thanks for all the helpful 'posts'!
  • albedo039albedo039 Posts: 3
    Will solution to vacuum hose problems described on here count for 1992 models as well?.
    My problem started with slow reaction on the vent lever, shifting it from position to position. This lasted for a couple of months, now it will not shift from AC to one of the upper positions (vent, blend, window) at all.
    On my car there are two hoses, not one. One black and one white that runs as described in previous postings over to the driver's side where it seems to go through the wall together with all the electrical wires into the cabin under the dashboard. They are both plenty long enough for alternate routings, and they are not even close to any hot parts that could make them melt.
    Opening the HVAC console (two screws), engine not running, and moving the lever, I could clearly hear the sound of vacuum shifting positions. The two vacuum hoses leading in to the console are one green and one black. They both seems to be OK. I disconnected them, and could clearly hear the suction, and feel it as well, closing the tube ends with my finger.
    Any ideas?
  • gpbillgpbill Posts: 1
    I have a 1995 Safari and the blower doesn't run. I replaced the switch, but that didn't work. Then I replaced the fuse and it worked for awhile, but now it has stopped blowing air again. Could it be the blower motor or possibly an electrical short?

    Any suggestions would be greatly appreciated.
  • well i got to say thank you to everyone i read most of this forum for my ac problem on my 2000 astro air blowing out of the defrost and ac/heat not working in the back . i replaced all 3 hose's like you all said and now it works great except the ac that is not cold . it is full of the freon but not cold can some one help thanks you this is a great help site .printman1691 :)
  • tedhousetedhouse Posts: 1
    I got a rock in the line running to the rear A/C, nicely venting all of my Freon (sorry atmosphere!) Actually it was gone before I got the van, buT I have a replacement set of lines. My problem is trying to disconnect it from the rear condenser. It looks like I have the nut I need to get off, but I can't separate the block old lines from the threaded stud that comes down from the condenser (I'm under the van at this point).

    Has anyone done this, or does anyone have a diagram I can look at to see what I am doing wrong?

  • lwquinnlwquinn Posts: 1
    Did you ever find out what was wrong with the blower cutting out? Mine did the same thing and finally the rear ac quit blowing altogether and the front ac only has the two highest settings.
  • My front blower for A/C & vent started not blowing when accelerating, then only blowing through the vents when coasting or when engine was lightly loaded. Now it hardly ever blows, you can hear the fan running, but no air comes out. The rear A/C blows cold air all the time so it's not a cooling issue, it's like a damper is closing stopping the air. Could this be a vacume problem? Is the blower "door" vacume operated or electric? How can I fix this without going to the dealer?
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