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LarryMart
Samba Member
Joined: April 19, 2022
Posts: 56
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 Posted: Sat Nov 25, 2023 8:49 am Post subject: cold defrost but hot heat |
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This morning with cold temps 25/-5c, 91 Multivan... temp control hot, defrost and heater split half way, fresh air off, vent open: Nice heat at feet and side vent, but cold defrost. Closed air on the floor and vent and still had cold defrost.
First cold temps with van , so idk about changes... I know the that defrost flapper closes and opens, but the temp is not warm (not as cold as outside air either)
Thanks!
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larry
91 Multivan |
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DanHoug
Samba Member
Joined: December 05, 2016
Posts: 4777
Location: Bemidji, MN
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| Posted: Sat Nov 25, 2023 11:28 am Post subject: Re: cold defrost but hot heat |
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| LarryMart wrote: |
I know the that defrost flapper closes and opens, but the temp is not warm (not as cold as outside air either)
Thanks! |
the defrost has been the coolest outlet on my 87 and is the canary in the coal mine in terms of heater core issues. here's some things to mull:
- try the defrost with most of the intake grill blocked and fan speed on one or two. or try it at a raised idle speed while stationary. if it is noticeably warmer, you have core and heater box issues. if the output is rilly rilly hot at the floor vents, this is important to know.
- poor heat output can also be from an aftermarket heater core. do you know the history?
- debris on top of the heater core and reduce heater output.
- cooling system sealer use sometime in the past 30 years can also reduce heater output.
- be very cautious on new heater cores. they just don't have the fin surface area needed to warm the huge amount of air coming in the intake. you are better off with a good, used, OE core.
- make sure your heater valve behind the radiator is fully opening.
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-dan
60% of what you find on the internet is wrong, including this post.
'87 Westy & '89 Westy both 2.1 4spd
Past projects can be found at--
www.thefixitworkshop.com |
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jlrftype7
Samba Member
Joined: July 24, 2018
Posts: 3577
Location: Chicago
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| Posted: Sun Nov 26, 2023 8:06 am Post subject: Re: cold defrost but hot heat |
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Since you have floor/feet heat, I suspect missing foam on the defrost or other internal flaps is allowing cold outside air to route around the heater core versus through it.
I will say however, with our different, earlier Heaterbox on our ‘84, even after replacing all the foam on the flaps, the floor heat seems hotter than defrost air.
I haven’t measured it with a thermometer though, but it seems hotter.
We gained a huge amount of efficiency with fresh foam on the flaps. Air volume through a given vent selection was so much better after the Heaterbox rebuild.
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'68 Westy- my first VW and vehicle/Bus- long gone.- sold it to a traveling Swiss couple....
'67 Type 3 Fastback, my 2nd car- gone
'69 Semi-Auto Stick Shift Beetle-gone
2017 MINI Coopers, our current DDs
‘84 Tin Top - Hilga....Auto |
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LarryMart
Samba Member
Joined: April 19, 2022
Posts: 56
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| Posted: Sun Nov 26, 2023 12:34 pm Post subject: Re: cold defrost but hot heat |
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Thank you,
I will put it on the do list.
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larry
91 Multivan |
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jlrftype7
Samba Member
Joined: July 24, 2018
Posts: 3577
Location: Chicago
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| Posted: Sun Nov 26, 2023 6:28 pm Post subject: Re: cold defrost but hot heat |
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| LarryMart wrote: |
Thank you,
I will put it on the do list. |
I tested Defrost and Footwell temps today while on the highway. Even with our rebuilt Heaterbox, there is a definite difference in defrost temp. It’s just not as hot as the air coming out of the foot/lower vents. FYI for you.
_________________
'68 Westy- my first VW and vehicle/Bus- long gone.- sold it to a traveling Swiss couple....
'67 Type 3 Fastback, my 2nd car- gone
'69 Semi-Auto Stick Shift Beetle-gone
2017 MINI Coopers, our current DDs
‘84 Tin Top - Hilga....Auto |
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