Why does my heat taper off?

Why does my heat taper off?

Postby tims1957 [OP] » February 14th 2010, 4:40am

Im new to the forum and new to the astro safari world. I just bought a 2000safari with the travel Quest conversion. I drove it home friday night. 45 minute ride and by the time i got home there was no longer any heat. tempgage read about 170. Sat morning put in a new 195 tstat,topped off antifreeze. Blew hot ait like a champ. gage read about 190ish. Drove it to dinner sat night, the air coming from the vents slowly got cooler and cooler.gage never moved. Im baffled. If it matters it has rear heat and a/c. Any suggestions are appreciated! :shrug:
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Re: Why does my heat taper off?

Postby Astroplane » February 14th 2010, 5:14am

LastCat is right on about checking the valve. :clap:
I had to edit my original reply because I told you what to check for on a '99 Blazer. Different system.
You are asking about the front core? Is the rear blowing heat like it should? You might still have air in the system. If it is completely filled and it still tapers off, the front core or valve may be restricted. Also check the vacuum lines near the A/C accumulator going to the valve and vacuum reserve ball.
Last edited by Astroplane on February 14th 2010, 7:41am, edited 1 time in total.
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Re: Why does my heat taper off?

Postby Lastcat » February 14th 2010, 5:57am

Check your Heater Valve. I had the same problem, I could always get heat to the back heater, but the front would get colder after the van warmed up. I was shutting the fan off, after 5 mins turn it back on, and get about a minute of heat, then it got cold. That valve is on the passenger side, near the firewall. I took mine out, and it had a rubber stopper that came off the shaft and was plugging the outlet to the front heater, I didn't replace the valve yet, but just removed the stuck rubber stopper. Next summer, I will have to replace that valve.

Well that's one idea, you could have a few other problems.

LC
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Re: Why does my heat taper off?

Postby tims1957 [OP] » February 14th 2010, 5:48pm

I checked it again this morning.Once the van warmed up i got luke warm air from the front vents. Cold air in the rear. Yesterday i had hot air from both at first. The front heater core has 2 lines going to it. Lower wich is bigger than the upper is hot,upper is cold. Maybe valve is partially open? allowing some heat?

Is there anywhere i can see a diagram of where all the hoses on that valve come and go to?
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Re: Why does my heat taper off?

Postby Astroplane » February 15th 2010, 5:08am

Take a look at the thread "No Rear Heat" in this forum.
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Re: Why does my heat taper off?

Postby astro355 » February 15th 2010, 10:32am

Diagnose 1st, never be a parts changer!

355 small block chevy w/ modified 700R4

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Re: Why does my heat taper off?

Postby Vinnie6 » February 16th 2010, 5:51am

I had the exact problem you are talking about - top heater core return hose cold. The rear heat was still working but slowly getting colder and colder. My problem was excessive sediment buildup in the dexcool, plugging the heater cores. Backflushing the heater core fixed it until it plugged up again (usually about three hours of run time). I finally licked it permanently when I had the entire system flushed out and replaced the coolant with propylene glycol instead of Dexcool. In my case the heater control valves were fine. What caused the sediment buildup in the dexcool? Air is what I am told. I suspect I had a bad radiator cap.
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Re: Why does my heat taper off?

Postby astroturf » February 27th 2010, 1:06am

Vinnie6 wrote:I had the exact problem you are talking about - top heater core return hose cold. The rear heat was still working but slowly getting colder and colder. My problem was excessive sediment buildup in the dexcool, plugging the heater cores. Backflushing the heater core fixed it until it plugged up again (usually about three hours of run time). I finally licked it permanently when I had the entire system flushed out and replaced the coolant with propylene glycol instead of Dexcool. In my case the heater control valves were fine. What caused the sediment buildup in the dexcool? Air is what I am told. I suspect I had a bad radiator cap.


Vinnie, What type of coolant did you go with? Thanks, Jim
My Cup is neither half empty nor half full... But has a hole in it. Holy Cup Holders Batman. LOLz, Jim
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Re: Why does my heat taper off?

Postby Vinnie6 » February 27th 2010, 3:39am

astroturf wrote:Vinnie, What type of coolant did you go with? Thanks, Jim


Amsoil, mixed 50/50 with distilled water.
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