What Are Reasons Why Your Heat Won't Work

[rich21]

1994 sc400. heat not working. i did the self diagonosis but everything was fine. i even tried switching the two vacuum hoses but those hoses are different sizes so that didn't even work... any advice?

[SKperformance]

there is an actuator on the firewall that has a small wire rod connecting to a black square valve it controls the flow of coolant throught e heater core.

If it doesn;t open then you get now hot air.

check to see if it is working

[rich21]

now i see that you have an es300 is it the same as sc400? do you have a pic that i can see so i know what to exactly look for?

[SKperformance]

Yup i have the camry

but toyota uses the same setups ,so it is located on the firewall more on the right side or passenger side.

[JPI]

There are a couple things to look for

1. Engine low on coolant

2. Mal-function Heater control valve(located on the firewall)

3. Air servor mixer(located by the evaporator)

JPI

[rich21]

engine coolant is fine. how would i check to see if it's the air mix servor mixer. and i still can't seem to mnow what the control valve looks like. is there a pic anywhere that i can see?

[rich21]

no one knows :(

[Sadistic]

Does the fan come on and blow cold air?

[rich21]

yeah the fan is running to what its suppose to be

[bartkat]

Does the engine temperature guage come up to normal? If not, the thermostat may be bad. The thermostat stays closed until the engine warms up, then it opens and allows coolant to circulate. If the thermostat is stuck open the engine won't warm up completely in cold weather and you won't get much heat from the heater.

This is usually easy to replace. It should be located near the water pump. Have someone check that out. They don't cost much and it''s worth it to just replace and see it it helps.

This is one of the most common problems causing a no heat condition.

[rich21]

the temperature gauge goes up to normal

[rich21]

ok i found the rod that you guys were talking about. now i pushed it in and there was a hose that connects to the valve, i saw build up of what it looks like old coolant the build up from when i had the radiator leak. now you guys told me that coolant has to pass through. is it possible thatwhen i put them radiator sealant additives that it could of clogged up that hose and thats why coolant is not passing through therefore im not having heat? hmmmm <_< anyone...

[bartkat]

Can you disconnect it and look inside? See if it's clogged and see if it opens and closes.

[rich21]

its a wierd clamp with a pin thats holding it in place don't want to try and take it out and having me lose it somwhere in the engine compartment. plus its 11 at night and its freeeeeeeeeeezing.

[bartkat]

Didn't say to do it now. If you don't know how, take to a shop. Sounds like you're onto something with that stop leak you put in there. We didn't know about that before.

[rich21]

im gonna have a mechanic check to see if thats the problem. i'll keep you posted, thanks for the help.

[alchemymike]

have the same problem on my sc400 everything works but no heat is blowing out mechanic still has car been there for two months

[osucool]

I had a similar problem with my 92 SC400.

Most cars have a vacuum controlled heater valve which opens when you turn the heater on (heater control valve).

Vacuum is supplied from the motor to this assembly and in this case is transfered to the valve mechanism, the valve opens and coolant is allowed to run through the heater core.

At least on my SC400 there is an electric switch that controls the vacuum going to the bulb of the switch. It is essentially an on/off switch for vacuum. When the switch gets power then the vacuum is directed to the valve. The electrical switch can be seperated from the mechanical valve.

Apparently this electric solenoid was faulty and not directing vacuum to the mechanical portion of the valve. If you have an ohmmeter tester then you can quickly test the two pins after unplugging the connector to the valve.

If this is your problem You have a couple of options

1.) Of course I don't recommend it but you could take the incoming vacuum line to the assembly and route it to the valve.

(Line from the motor to the top of the valve where the line from the electrical assembly runs to.) I am not sure if this will work properly or not.

2.) I went to a salvage yard and found a vacuum switch that was on old honda civic 92 maybe (I think used for the motor mounts vibration?) $4 bucks at U-pull it-- the thing is right out in the open near the firewall-- one 10mm bolt and two vacuum hoses.

I replaced the faulty Nippendenso part with this item and all works perfectly. Size is pretty similar so it is not a noticeable hack job.

3.) I think the dealer wanted $450 for this assembly which consists of the electrical solenoid and the mechanical valve.

Maybe this will help , if not then good luck and try not to freeze.

[rich21]

thats what i did i rerouted the vacuum line to the heater control valve and now i have heat thank god. going to leave it like that for the winter. so thats what i would alchemymike for the winter, t least you would have heat.

[McGowen]

I have a lack of heat problem as well. Here are my symptoms.

1) The firewall mounted valve seems to be working. I can see it actuate when the heat is turned on.

2) The engine temperature goes to normal and does not overheat.

3) The heater works when the engine is running over 2000 RPM.

4) The heater goes cold at idle.

5) The thermostat has been replaced.

6) There is coolant in the reservoir, so I believe the system has plenty coolant.

Any help would be appreciated.

Thank you, C.W.

[Marty Witt]

I lost my heat for a few minutes the other day. To give a little background, I had my antifreeze changed about 10 days ago. They used a fancy gizmo to suck out the old while putting in the new at the same time. When they finished, I asked if they were going to burp or bleed the system to remove air from the block. He said they did not have to do that with this fancy system. Anyway, for about 8 days everything seemed fine, until I stomped on the gas after the light turned green. All of a sudden, I could feel my air getting colder and colder. I pulled over and revved the engine and I could hear gurgling noises. I thought I had a leak. Finally the gurgling stopped and the air started to get warmer and warmer. Now all is well again. I think my engine needed to burp!!! So, If I were you, I would try opening the bolt near the top and front of the engine to remove air from the block. I think you do this slowly while the engine is running, but don't quote me on that.

[osucool]

My first guess would be a faulty or cracked vacuum hose. As you know vacuum would increase as engine rpms rise.

Intermittent problems are the worst.

Good luck

[alchemymike]

Are you sure your not getting any errors on your climate control? check the sunload sensor followed by the in car ambient air flow sensor mine did the same- no heat and had a bad sunload sensor