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Discussion Starter · #21 ·
:oops: sorry, I meant console
 

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So your talking about the hoses/connected to the switch???? Because I have removed the whole dog house without seeing any hoses. Does anyone have a pic of what we are talking about. I'm sure it's easy. It's gonna be 97 today. If there's any chance that I can get this working it would save me n my son.

Thanks in advance
 

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Awwww. The hoses were stuffed behind the radio.
Ok so I have the dash open the counsel off and everything looks good. If I turn it on and twist both the fan speed switch and the ac to def switch I get a lil bit of sound as if it was gonna swing into AC/vent mode but no go.

Anything else before I replace the switches ???
 

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Discussion Starter · #25 ·
It's above my knowledge now.
 

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Dealing with an issue with no defrost. Lucky me, it's December. There are two vacuum operated doors for heat control...one for floor and one for front vent and defrost. My defrost decided it was cheap white plastic and the nub that the actuator connects to decided to break off. The actuator end is metal of course :roll:

Currently trying to figure out if I can get access without damaging the system, but it looks unlikely. The blend door for defrost will fall to panel vents due to its weight and fulcrum, but if it is pushed up it will catch air and stay open as long as the van is on and the air is running. At this point, all I care about is defrost because I never use the panel vents, so I think I'm going to rig up something to keep it open or close to open so that the fan can finish opening it. I'll have to remove the dash to get proper access to it to repair it, which means I'll likely either have to rebuild the control arm thingy or rob one out of another JY Astro, not something I plan to do anytime soon. Took a while to figure it out, but a little listening and a flashlight saved the day..sort of.
 

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Fact gathering. I got the defrost to stay on defrost without affecting anything else in the system, but lo and behold my system seems to be falling apart. We had no heat at idle the night before, this morning I had heat all the way to work. On the way home, no heat. I got home and started digging around, discovered the 6 way gang valve leaking/falling apart. Replaced that figuring the loss of pressure in the system was causing the problem, because I would get heat at higher rpm forcing fluid into the heater core.

After replacing the valve assembly, now I still have no front heat. Rear heat works just fine. Problem is, the heater core lines aren't as hot as the rest of the system. I'm holding good pressure as the upper radiator hose was firm. I'm beginning to wonder about the heater core. I think perhaps I've got an obstruction or ??? Plan to back flush the heater core ASAP and will post to this thread.

Symptoms were. No defrost control, dash vents and floor heat...lots of heat though..front and rear( repaired/found bad defroster door arm..wedged open with foam and topped off coolant). It switched to Defrost and floor control, no heat at idle, rear heat still working fine, front heat at highway speeds ( van sat overnight ). Then it switched to front heat at idle, heat at speed both front and back ( replaced gang valve and topped off lost fluid ). Now I have no heat in front, but rear heat. WTF is going on ??? Perhaps I'll have heat in the morning.
 

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SOLVED! Okay gang, for those that have the same "duh" moment and can't quite figure it out, I did today. I had the exact same problem on another GM van...WOT under load and you get heat, but at idle, ice cold.

Here's the solution. The vacuum operated valve for the front heater core is operated in such a manner that vacuum is NOT applied to it when heat is desired, unlike the REAR heater valve which requires vacuum in order to open up and allow heat to go to the rear. It makes sense when you think about how the whole system is engineered, but it's overly complicated in the parts that are used.

Here's the rub. At WOT, vacuum is lost. I had had the jumble of vacuum lines all screwed up as well as the previous owner. The large rubber vacuum line with the two holes in it that come from the firewall work like this. The upper hole is for vacuum to be supplied to, meaning that vacuum sucks everything from within the passenger compartment out to the motor. The lower hole is to cause vacuum to be applied back towards the engine, which is directed that way by an orifice that changes when you select from HEAT to COOL on the position knob.

So, the lower hose goes to the vacuum operated valve and when vacuum is applied, it CLOSES the flow of coolant, which equals NO HEAT. The upper hole has the vacuum ball, the vacuum source with check valve and the rear heat vacuum line connected to it.

What I had done is hook up the lower hole to the vacuum ball, and the rest to the heater core valve, rear heater core valve and the vacuum source ( motor ).

So, when I would change RPM, you would notice sometimes that the defrost would come on instead of the dash vents where the selector was.

Apparently my connections were shoddy and the vacuum source would jump all over the place and cause it to work in random ways. I now have heat when I want it, where I want it ( short of the temporary-soon to be permanent-fix to the broken defrost/panel blend door arm. )

And as it turns out, it also repaired my P0171, P0174 lean bank cylinder problems, because hey, no vacuum leak!

So, all things considered, a little discomfort for a couple of days to kick me in the pants...I fixed a nagging long term problem and learned something about the HVAC system!
 

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My van blows warm air out of the vents but doesn't get hot. I just got this van a few days ago. Thinking it's good possibility that the heater core is plugged up. The guy I bought this from only drove highway an chased oil every 3k. The van never had plugs wires cap rotor. An runs well a 156k.
 

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with the van up to operating temps, check the two hoses going into and out of the heater core. They should be the same temperature if water is flowing through it. If one is warm and the other is cooler, then you have a restriction, a plugged core, or an inoperative valve.

Does the van have green coolant or Dexcool in it still? If it was switched to green and the old Dexcool wasn't fully flushed, you could have a build up of gunk in the heater control valve which is restricting flow. Do you have only front heat and not rear?
 

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Quick note on this from my experience just now...

I got my astro without the doghouse installed, so put that in myself. Turns out, those 4 air hoses run right through there. My selector wouldn't work, went through all the lines under the hood, saw they were already replaced and had vacuum. Took the interior apart, checked it, everything worked fine. Had the lines pinched off, so rerouted them and put it all back together.
 

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That fixed mine. I would thank all the contributors to this problem but there are multiple posts on this subject. Rerouted the vaccum line up high so that it doesn't lay on the intake manifold and get crispy so fast. Any thing rubber or plastic in that engine comp will get brittle eventually but thought it would last longer ziptied to the wiring harness above the engine.
 

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Just wanted to say thanks for this post. The colored lines diagram on the first page helped me trace where the bottom line actually went to (the vacuum canister), as I inadvertently ripped it out when removing the top line (to engine) that went brittle and broke. As others have said, access to the canister is through the wheel well. Just take the wheel off, and look behind the splash guards. It's mounted with 2 screws. I took mine off to reattach the hose I ripped off, and saw that the port had been jerry rigged in the past, so I replaced the whole thing.

Yea! All my air vents work again! I'm ready for the rest of the summer, but mostly for winter (in Alaska).
 

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I appreciate that picture. I have a 2004 Safari, is that considered Gen II? As in Return of the Geni? My issue (well my van's issue) is an apparent "weepy leak" from the HEATER CONTROL VALVE . FYI - I have rear heat (which has not worked in years) so I assume I will need the 6 outlet control valve? I really can't see the darn thing, that is for sure.

My next question is: this looks like a real tough job and I do know that even touching a vacuum hose is "system death"?

I am pondering this job , my mechanic said "i shouldn't drive it" with a (what he says) is a cracked plastic valve that will blow up at the worst time (like on a the Lions Gate bridge in rush hour) but well.... i drive it all the time, I just keep a jug of water handy and keep filling. That said I know "it" must be fixed but I really don't feel like giving mechanoman my van for a whole day . I know he wants a new Laptop and I smell "hours of labour" and a big $$$ bill!

any advice from you safari nuts is appreciated!!!
 

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Yep, 6 outlet. And you replace it through the passenger-side wheel well, as stated above. Much easier to get to.
 

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Thank you Leeann_93 for your informative post regarding replacing the Safari 2004 Heater Control. I show the part number:

FOUR SEASONS 74853 Heater Valve Info
Front; w/ 6-Port Hose Connection

Costs about $33.00

I assume your first take off the Passenger Wheel - then the wheel well itself? That would make sense as I cant really see any other way to get at that unit - way too much stuff in the way . I assume the FAN HOOD has to go as well -- that always seems to be a part that is in the way.

Thanks again for your kind advice.
 

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You don't have to remove the wheel, but it does let you get closer to the work. And yes, pop off the wheel well cover.
 

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Jasen,
I have rear heat and air, but nothing up front. I know the post I'm replying to is 4 years old, but I need assistance in fixing my issue with HVAC. If you have pics related to this fix please send them. Also, I'm tackling the door handles and door puns and bushings. Pics would help there as well. 2001 GMC Safari 2WD LT. Please feel free to email me at [email protected]. Please put Astrosafari as email heading so that I know who/what it is. Thanks!
 
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