Question about 2000 Chevrolet Express Cargo

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Heater problems My heater core has hot water flowing thru it but cant get the damper to open with a call for heat. Is there a easy way to manually open the damper without tearing everything apart?

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  • hvacmanr22 Dec 13, 2008

    vacuum operated it used to work for a while then stop then start working again now it wont open the damper. i do know the heater core is getting water thru it as it is plenty hot. the air bi-passes the heater core as if it is in a/c or vent mode

  • Mike Butler
    Mike Butler May 11, 2010

    can you tell , or do you know for sure whether it's vacuum or electrically operated?



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If you can get a hold of that vacuum motor/valve, and move the rod in the right direction, up, down, back, forth whatever, then zip-tie, or wire it in place for now. You should be able to feel or hear the difference as you go, if yu can safely run heater while you do it.

Posted on Dec 13, 2008


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1 Answer

Heater core hot but not in cabin

the damper at the core must be open,
so the rules are" (heat exchangers) 101
1: hot engine, yes.
2: hot core, yes. (water must flow and both tubes hot to core)
3: air flow through core, not. (fix cause, if blower is running on high
then the damper is closed.
do you need a drawing? the FSM covers that , all cars, factory service manual even shows every step, in diagnosis.
1990 is a toyota corolla. so books on that car , match too.. hint?

they make 2 kinds if 1990
one with cable damper (temp)
and with water valve. got valve>y/n, no then its damper
this is a cable car, so the cable must move the valve or the damper
open fully to get hot air

valve below. (1990 corolla book)

using 2 persons, make sure the valve works
and is not clogged inside. it.


Feb 18, 2015 | 1990 Geo Prizm

1 Answer

Truck will only heat for a minute then quits

make sure hot water is flowing thru the heater core by feeling both hoses, in and out, both should be hot. if not, maybe the valve is not opening to allow the water to flow. If both hoses are hot then maybe the heater valves are not working and you are just bringing in cold outside air instead of the air flowing thru the heater core and providing heater air. Could also be a sensor in the heater that thinks it is a lot warmer than it really is.

Feb 17, 2015 | Cars & Trucks

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2005 gmc savanna van...cooling system will not blow hot heat. water pump,heater core,radaitor and thrmostate replaced. is there any electrical problems/

don't know this van specifically, but some things to check, make sure cabin filter is replaced or clean, you didn't say if the blower itself works, if not, correct or replace. Check the hoses going to the heater core, if hot water is flowing thru the core, both hoses should be hot. Check the heater controls to make sure doors in the system are opening closing as they should, you may just be drawing in cold air and not going thru the heater core.

Feb 11, 2015 | 2005 GMC Savana

1 Answer

Car has no heat a little sometimes

it only takes 3 things to get heat.
1: engine at 180F or more holdind, IS IT?
2: that coolant flowing through the heater core, (water valve open)
3: fan blowing air through said core. IS IT?

first see if your car has a water valve. 1/2 the cars have it others only
have an air damper.
so look for water valve, at the hose fire wall.
are both hoses hot , at near 180f? if not its blocked.
if both are hot, then the dampers is stuck closed.


Feb 13, 2014 | 2006 Acura MDX

1 Answer

2009 jeep patriot not heating up properly

its a heat exhanger.
1: the water is not 180F or more.
2: the water is not flowing through the core
3: or the air cant pass through the core.
bad water temp,. bad flows, or the damper is in the wrong position.

i plug in my scan tool and the ECT reads 180f or more. holding
cool real hot water.
i then feel both water lines to the core (dial set to hot)
both are hot, if not , the core is plugged or the water valve (if present)
is clogged.
ok both lines 180f roasting hot, finger test or better IR pyro gun.,
must be damper stuck blocking core, or huge mouse nest inside.

if the core is hot, we check damper controls
there are 3 systems, and some cars have a mix
open FSM to HVAC section,, bingo there you go...
cable, vacuum servo and damper motors.
some are a mix. min 04 is mix. my jeep 08 is vacuum
my 96 is cables.
id dont matter,. there is a simple test for each
the motor kind are the hair pulling kind, (invisible)

i went online
the patriot has at least 2 cables, blend./temp, and mode
so there is water valve, so he damper if open on temp you get
full heat, just eyes on that lever ,cable and end of cable tells
you if the door is opening.

Feb 05, 2014 | 2009 Jeep Patriot

1 Answer

1998 jeep wrangler blows out cool air

you can answer the valve question your self. just look, at the 2 hoses
to the heater core. its there, or not.
the 1998 is here.
see cooling and HVAC sections, as i see , (no engine stated)
there is no valve in the engine bay.
page 7-2 , see that?
then see HVAC page.
if hot water flows thru the core. then the dampers are stuck (why takes tests)
car has 3 vacuum servos, they can be watched to see if each works
page 24-38 (chapter 24 hvac, end)

in an emergancy you can force any vacuum servo to do what you want with bailing wire or tie wraps.
force dampers to heat max. no recirc, and what ever direction you want. on cars with no hot water valve, (this car)
they have a heat damper, yours is stuck closed.
the H/C lever, moves this damper, open and closed.
make it so.

Jan 26, 2014 | 1998 Jeep Wrangler

1 Answer

Heat wont work

never post a car with no year, they make changes every year.
1990 to 2002 , ? and is a Toy Corolla in Snake skins(geo)
geo was 90-97/ only. 1.6L or 1.8L?
like heater water valves, or heater damper only heat controls.
so the fan runs at full speed?
the engine gets to 180F and holds?
ok not knowing year, ever see the 2 hose from engine side, to
cab side heater core. the that pass thru? well that is the cab core.
and you get engine hot and touch both hoses. are they both hot
yes, good, if not we work that.
this take like 1 min to do , after engine is hot and works on all cars.
1996 major changes. so?

here is a no year, answer on the controls
when you move each lever, it move a cable (does it) and if does
does the end of each cable move an object.
1: a water valve.
2: a blend door.

the cable has 2 end, either end can fail.
the cable has sheath, just like a bicycle and works the same way.
the sheath is has clamps if broke the cable is rendered useless.
use tie warp to clamp this floating sheath to any near object.
done many.
on old cars, i back flush all coolant paths and test the water valve if found. then when all together I have full flow through the heater core.
one guy had mouse nest in core, blocking it.
the system is real simple
hot water must flow thru the heater core. at 180F or more.
and air must flow through the out side of this core and past
all the way through it, and arrive at the vents
if the core is hot, then the flow is bad.
bad damper ,mouse nets. or some pack with leaves.
you now have all you need to fix it.

read this, they mostly bounce off walls but find it.

Dec 18, 2013 | Geo Prizm Cars & Trucks

1 Answer

No heat blower moter blowing cold air,temp on max 91, fluid is full fuses are fine car temp running good in the middle motor fan work on and off like its supossed to . i just cant figure it out and BMW...

ok the heater cor needs to bet hot, if not , no heat.
you can put hand on both tubes, of the core of any car.
do so, are the they both hot.
no, (the heater valve is closed or packed up, (no service? every 2 years)
yes then the heater, controls are bad, (bad controller or the damper flaps , motors (or cables, vacuum) controls are malfing.
lets do the flow (no pun)
1: hot engine, 180F holding or more.
2: fan blows
3: hot water flowing through the heater core....
4: dampers in the right position.
just 4 checks, find the one that fails in this order and the job
is less work, and to the real cause.

id didnt go to to look at what type of controls you have.
we can, (so can you) if test 3 passes.
some cars have core valve , find yours and make sure it flows.
other cars there is no valve. and only the dampers block heat.

Nov 30, 2013 | 2001 BMW 325i

1 Answer

Heater does not work have flushed engine changed thermostat and heat flapper valve

the problem maybe heater core stopped-up. need to see if coolant is flowing thru heater core.and check to see if heater hoses are getting hot near heater core . if take off heater hoses to core with water hose run water thru one side of the hoses to see if water flows thru the other hose.

Nov 19, 2010 | 1998 Ford Econoline

1 Answer

No heat,ch.thermostat,water is circulating,blower goin strong .

Check the 'heater control valve'. This valve opens when u turn on the heat switch on the dash, so the hot coolant will flow thru the heater core and provide heat. So although the coolant is circulating in the engine, the valve controlling the flow to the heater core is stuck closed, or not working.

Nov 15, 2008 | 2000 Ford Focus

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