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What if one of the hoses thats hooked to your heater core is hot and the other is cold what does that mean

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Posted on Dec 11, 2012


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SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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Posted on Jan 02, 2017

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SOURCE: 1999 chevy truck, blows cool air only,

yes it could be. you should look under the dash if possible and see if you see the levers for the doors switching.You may possibly have a weak actuator.

Posted on Nov 11, 2009

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SOURCE: Poor coolant flow through heater core. Heater core

on some GMC models there is a valve that opens when you turn on the heat inside. It is called a heater control / actuator valve, it works off engine vacuum thru hoses connected under the dash, and going to the top of the valve. Now junk and crud and old rust will get in the valve and restrict it's flow. You will have to pull the valve off and clean it, but it is best to replace it, seeing it is hard to get all the junk out of it.
It looks like a L shape pipe with a hose on top & bottom, black plastic,and a smaller line on top mounted close to the wheel well about even with the exhaust manifold on the pass side. Drain the coolant, remove the valve and see if this is the cause, lots of gunk in the one hose. It is not real hard not real easy to replace this valve. Now if your truck does not have this valve check the pipe that the hose hooks to on top of the engine, remove the hose and see if a small screw driver will go down inside or if it is stopped up. .

Posted on Dec 07, 2009

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SOURCE: Heater doesnt work blows cold air, replaced

This is what I did to solve the exact same problem.I got a pump that you can hook to a drill that has garden hose connections on it.I made 2 hoses to pump into my heater core and hook to the pump. I bought some radiator cleaner at Auto Zone and put it in a 5 gallon pail with about 2 gallons of hot water.I pumped the cleaner from the pail into the OUTLET side of the heater core.(By going in the outlet side you are back flushing the core.) I put an old cloth over the top of the bucket and let the outcoming cleaner run onto this cloth acting as a filter for the dirt coming out of the heater core and let the pump run about 10 minutes. Believe me,A LOT!!!!!!!!!!! of dirt,rust etc. came out of my heater core. The heat now works excellent! Good luck.

Posted on Jan 29, 2010

  • 87 Answers

SOURCE: heater blows cold

ok there is a few things might be happening...first did you make sure when you put the intake gaskets in there was No ports plugged or covered...second is...are both heater hoses Cold or is one hot and other cold...if so you have a air lock in the heater core...if this is the problem you need to lossen off the cold one till antifrezze comes out.

Posted on Mar 06, 2010

  • 4669 Answers

SOURCE: no heat top radiator

Have you tried backflushing the heater core?

Posted on Nov 04, 2010

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1 Answer

No heat, only cold air. AC works.Heater core/hoses fine. Havent heard thumping and actuator arm slowly rotates when I turn temperature dial. Doesnt that mean the actuator is working?

check the heater hoses after running the van for it to get hot . if they are not getting hot then the heater core is plugged up

Nov 20, 2015 | 1998 Ford Windstar

2 Answers

Why doesn't rear heater work?

Sounds like a blocked heater core. Could be different reasons. You get any check engine lights? If not, you may want to back flush the heater core by using a garden hose and adapter you can get at an auto supply store. You would hook up a running garden hose to the side that is cold and hopefully the prtessure would unblock any sediment or blockage.

Oct 20, 2015 | Cars & Trucks

1 Answer

2000 chevy silverado not blowing hot air

1: not enough liquid in the system (air in the heater core)
2: inoperative heater valve not allowing hot liquid into the core
3: hot/cold blend door in the heater box stuck on cold
4: clogged heater core
A clogged heater core will have one hot hose and one significantly cooler hose at the firewall connection; easily tested by hand. a good core will have both hoses very hot to the touch when the heater is on full blast.
Make sure that the system is full and at operating temperature, and the heater controls set on full heat. Feel the hoses at the firewall; if they are both too hot to touch then the problem is in the heater box or controls.

Mar 03, 2013 | Cars & Trucks

1 Answer

1995 jeep cherokee heater problems

Get jeep up to operating temp
Turn on heater to max heat
Hood feel 2 heater core hoses goint into upper passenger side of engine compartment firewall.
They should feel too hot to hold
If it's not hot, could be 6 things
1. heater control valve is bad
2. Vacuum to heater control valve is bad
3. clogged heater core.
4. Bad thermostat
5. Bad waterpump
6. Needs more coolant (check when system is cold)

Do these things:

1. Disconnect vacuum line from control valve and feel under valve to manually move valve to open position. This should let hot water flow through core. If you now have heat inside, replace the heater control valve. Or you can disconnect the plunger on the heater control that is hooked on to the silver bar on the bottom of it. With it disconnected you can manually move it to the open position. It will always remain on.

2. When system is cold, disconnect both heater hoses going to heater core. hook up a water hose to one side of heater core and flush out any gunk. When you get done, the water should run clear. If you see lots of gunk come out, that was probably the problem. Replacement is like $20-30

3. When system is hot and engine running, squeeze the upper radiator hose (using gloves) when you release it you should feel a surge of water. Proves your water pump is working. If no surge, check thermostat. If thermostat checks good, look at the weep holes at the bottom of the water pump for traces of antifreeze. If you see a trace or stream of coolant, indicates bad pump.

4. As far as testing the thermostat, watch as your engine heats up on the gauge. when it gets to a certain point you will see the temperature rise, then lower, then rise again. This means your thermostat opened properly, cooling the system temporarily, then heated it back up. Replacement is around $5

Try these and see how it goes.

Feb 01, 2012 | 1995 Jeep Cherokee

1 Answer

What if the heater hose going in is hot and the heater hose coming out is cold.the heater will blow cold air

Possibly the heater core is 90% blocked. open enough to draw hot water in, (hose feels hot) but not enough volume to provide heat from very cold air, 10% hot water gets cold quick, coming from core..
Flush heater core in reverse direction - cold side in hot side out..

Just a theory..

Dec 14, 2010 | 2000 Chevrolet Silverado

1 Answer

Little or no heat.

you have two hoses leaving the firewall and going to a bypass just under the alternator they are your input and out to your heater core feel them both when the vehicle is at operating temp if ones hot and the other is cold backflush the heater core by hooking a hose to the cold side and force water through the heater core make sure to disconnect both hoses before flushing though

Oct 31, 2010 | 2005 Pontiac Grand Prix

1 Answer

I do not get any heat from the heater

Do you get air out the vents in your Blazer with the heater switches on? If so then open up the hood of your vehicle and with the heater running in the on position feel the hoses going into the heater core on the passengers side just ahead of the glove box under the hood. See if one hose is hot and then feel the other and see if it is hot or cold. If one is hot and the other is cold the heater core is plugged up and needs to be replaced. Now sometimes if they are not real bad you can have a place that works on or repairs radiators hook up to the heater hoses and they can sometimes make the heater core start working again. We have done this on several occasions with great success. Depends on how bad it is.

Dec 04, 2009 | 1998 Chevrolet Blazer

1 Answer

Heater blows cold air.

heater cores clog in taurus. way to know is this--engine fully hot--heat on reach down to the fire wall and grab hold of one of the heater hoses where it hooks to the core--one should be real hard to keep hold of because its that hot. If the other is close to the same the core is not clogged. But if the other is cold to the touch its clogged. You can remove the hoses and shoot garden hose water in one side or the other and break it loose usually

Apr 07, 2009 | 2002 Ford Taurus

2 Answers

1998 jeep cherokeesport

Follow these steps:

Check coolant level, then start engine until it is warm and the thermostat opens. You will tell when it does when the needle on your temp gauge goes cold when it reaches around 180-200* and then goes back up. Now turn on your heater full blast and go to the engine compartment. You will see a heater valve located on the passenger side, next to the washer reservoir. It is a black thing with 4 heater hoses connected to it. Feel the hoses. When everything is working correctly it should be like this:

Hose going to waterpump will be hot
Hose going to (I think the thermostat housing) will be hot
2 Hoses going to heater core (mounted behind firewall) will be hot

1. If only 1 heater core hose is hot, heater core is clogged--
UNCLOG: remove 2 hoses going to heater core when engine is cool, hook water hose end to one of the sides and flush out gunk from heater core. Reconnect hose and you should be good.

2. If neither hose core hose is hot, heater control valve is bad or vacuum is bad--
Test Vacuum: remove vacuum line from heater control valve, you should feel the vacuum **** on it when pressed to your cheek and the heater control valve actuator should move when you unhook the vacuum line. If you have a good vacuum, it's probable the valve available at autozone part # 5941 for around $21.

To get heat while you wait to replace part, unhook silver arm on heater control valve that is hooked to the plunger. This will give you heat all of the time, but it is controlled by the bottom hot/cold switch on your heater control unit so you won't get hot in the cab. It will just circulate heat through the core.

Oct 25, 2008 | 1998 Jeep Cherokee

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