no vacuum to heater control valve problem on 02

no vacuum to heater control valve problem on 02

Postby Vinnie6 [OP] » December 10th 2009, 5:43am

Trying to troubleshoot a low-heat situation. Thought I had it licked, but I was still not happy with the amount of heat I am getting on the floor. Tonight I made a major breakthrough. I'll cut to the chase: no vacuum to the heater control valve. Obviously the next step is to find out why. The vacuum line is really thin and goes straight to the firewall, so the problem must be up inside the dash. It's a 2002 Astro. Any ideas as to what I need to do to troubleshoot this? I have absolutely no experience in this area. I am making a really big assumption here - bordering on sounding stupid - but, the heater control valve is supposed to open when the heat is turned up, right?
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Re: no vacuum to heater control valve problem on 02

Postby Vinnie6 [OP] » December 12th 2009, 7:18am

Well, here is my update: In trying to solve my low-heat situation, I went looking for vacuum line problems - found nothing wrong anywhere. Pulled the doghouse even. THEN I was under the hood again looking at vacuum hoses. That is when I found the hose that goes to the vacuum ball had somehow come off the vacuum ball. It went back on, but is plenty cracked and needs replacing. I also learned that it is the COOL setting that opens the heater control valve - when your temp is set to hot, the valve stays closed. I wish I had learned these things before taking things all apart! I have no vacuum problems. Everything seems to be working as it should. I went for a drive before putting the doghouse back on to see how much heat I would have. Now that was an experience! Reminded me of the motorcycle days. That is one loud engine when under load! Cool! Wish I could always listen to that. I seem to have normal heat now, but won't know for sure until I get her on the road for few miles. The burning question is - can a vacuum hose coming off the vacuum ball cause a reduced heat situation? Anyone know the answer?
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Re: no vacuum to heater control valve problem on 02

Postby Vinnie6 [OP] » December 12th 2009, 7:50pm

Still low heat. I'm going to replace the heater core later today. Everything else is working PERFECTLY.
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Re: no vacuum to heater control valve problem on 02

Postby Vinnie6 [OP] » December 13th 2009, 7:11am

Wasn't the heater core either. Still not blasting heat like I am accustomed to. Tomorrow I will change out the heater control valve even though it works. Maybe it's plugged. Seems to be a common occurrence from my reading other topics. That's all that's left to try.
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Re: no vacuum to heater control valve problem on 02

Postby jeff's93astro » December 13th 2009, 7:18am

where does your temp guage sit your thermostat could be sticking open or opening to soon making the motor run cooler and make you have low heat
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Re: no vacuum to heater control valve problem on 02

Postby Vinnie6 [OP] » December 13th 2009, 4:03pm

Jeff,

Thanks for asking. It's one dash to the left of 210.
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Re: no vacuum to heater control valve problem on 02

Postby Vinnie6 [OP] » December 13th 2009, 9:42pm

Well, I put in a new heater control valve. Not an easy task! 90% of the time is spent getting the pliars on the hose clamps and moving them. I previously found some very crumbly old vacuum lines around the rear heat solenoid looking thing and the air canister ball, so those are replaced now. The old heater control valve, however, looked great. It was clean as can be on the inside. After putting things back together, I went for a drive and the heat was fluxuating between warm and cold. Air has to work its way out of the cooling system. I tend to believe it was air in the heater core all along. In the last five days I have removed and inspected the heat controls in the dash, removed the dog house and inspected vacuum lines, replaced the heater core, and replaced the heater control valve. I still do not have heat like I used to, before the dealer replaced my thermostat. What else can it be?
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Re: no vacuum to heater control valve problem on 02

Postby jeff's93astro » December 14th 2009, 1:34am

i believe you may just have air in the system get the front end up in the air while its cold take rad cap off and crank it and see if you can get some of the air out
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Re: no vacuum to heater control valve problem on 02

Postby wob1 » March 24th 2013, 2:30pm

I had similar issue ...had to replace all the vaccum pipes even the one that goes to the vac ball near the RHS wheel hub (remove inner wing protector) to get to this as was fully perished when I got to it ...now heater works fine and can now adjust from screen to in car and also foot well directions. Replace all the pipes in the engine bay first.
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Re: no vacuum to heater control valve problem on 02

Postby swharris » April 11th 2013, 5:57pm

Check for LOW coolant level in the cooling system. I had that happen once. Had a leak in a heater hose. Most of the coolant had leaked out and I had no idea. The only way I noticed it, was because the heater stopped blowing hot air continuously. It would work briefly when I rounded a corner, and it dawned on me that coolant was only getting to the core intermittently. Haha. Truck was not over heating because it was the middle of winter.
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Re: no vacuum to heater control valve problem on 02

Postby redfury » April 12th 2013, 12:50am

Do you get more heat when the engine RPM's are higher?
A temporary fix usually becomes a permanent solution, therefore it does not exist.
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Re: no vacuum to heater control valve problem on 02

Postby Don1806 » April 14th 2013, 2:20am

Based on my experiences with a 99, it can be a couple of things. Low coolant / air in system that still needs to be burped out, cracks in a vacuum elbow if the lines are good. The elbows get microscopic cracks in them that you cant see without really manipulating them, but when the temp gets hot under the hood the cracks expand and cause a vacuum leak.

My Astro runs nowhere near that hot. What temp thermostat did they put in and is it opening and closing as it should? Since that's when your problem started, that would be my prime suspect along with air in the system.
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Re: no vacuum to heater control valve problem on 02

Postby Leeann_93 » April 14th 2013, 3:15am

One dash to the left of 210° is correct. They take a 195° t-stat.
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