Hey guys this is for a freind of mine.
She has a 92 Sc400 and there is no heat. The AC works fine when you turn it to auto and like 65 all the bars go up. But hwen you turn it to like 75 or 80 the bars all go away and the fan just blows cold air. Also from time to time the radiator light comes on but there is no overheating. If it makes a differfence the car has 78k miles. I have three guesses right now:
1. Air pocket in system not alowing coolant to heater core.(Going to flush coolant tommorow)
2.Heater Control Valve not operatiing correctly. I will look at this tommorow. I belive the 92's used a cable insted of a motor for the valve to open.
3. Something wrong with cabin temp sensor.

Any ideas or other guesses?
Thanks for any help!

Also if you raise the bars manually it still blows cold air.

 

I had sa,e problem for my 93' SC 300. The dealer diagnosed as bad VSV for heater valve. The dealer replaced for $400.00.

I hope this help.

pc

 

Also when you floor the car then warm air comes out. Does this mean the coolant just has to be flushed?

 

This is exactly the same problem on my girlfriend's car. Everything is normal with the climate controls, except that when she tries to turn the heat on, no hot air come out of the vents. Even if she turns the temperature to "HOT", the air is still cool.

So please tell me where the Heater Control Valve is.

Thanks in advance.

 

SEARCH people, SEARCH! One of two problems. Low coolant, causing vapor lock. Or, the heater control valve is bad. $278.00 from Steve Ganz @ carson toyota. Its a common problem. Flushing might help.

 

Top off your coolant wether it needs it or not; you'll be surprised!


Keith

 

A second for "top off your coolant reservoir" before you start buying parts.

 

Tell your friend to move out here to Phoenix, AZ. Out here you never need a heater, all you need is a damn good A/C.

 

On my '93 SC300 (when the heat stopped working), I took the vacuum line off the VSV switch and moved it directly to the heater valve vacuum canister (not sure about part names). The heater has worked fine, both in auto & manual modes (system still waits for coolant to warm before ramping up fan speed, if I remember correctly).

Anybody know the function/purpose of the (non-working) vacuum switch that I bypassed?

TIA,
Tim

 

Now thats a new one. Which hose did you relocate and where did you attatch it to on the canister?

 

I had same prob in my 93 SC400. Took it to Toyota and they replaced the VSV valve. Think it cose about $250

 

Camshaft,

The "switch" has two vacuum ports on it, and a two-wire connector (I think it's 2-wire). Anyway, one short hose from the switch leads right to the canister (heater valve), the other (long one) has vacuum present. Since the hose leading to the canister did not have vacuum, I simply connected the one with vacuum directly to the canister (right on top), and voila -- functioning heat.

I'd recently installed a VintageAir heater into a project car I'm building, its heater valve is also vacuum controlled.

It seems then, the function/purpose of the (VSV) switch is to allow coolant to circulate through the heater core "only when needed?" (by activating heater valve) Again, my heater/AC controls still work just as well as they always have.

HTH,
Tim

 

Sure beats the hell out of spending $250 if you live in an area that is colder. In warmer areas, you would not need the fluid flowing through the core all the time.

 

I'm serious guys, try topping off the coolant before anyone buys anything. Everyone has some spare coolant lying around, if not the distilled water is only .59 cents per gallon.

My coolant appeared completely full when I had the same problem. I added maybe 2 oz. of coolant and--> voila! Heater worked again. About 2 years passed, same problem.......coolant Appears completely full, top it off anyaway, again - Heater is working fine. I can't explain why adding so little coolant can solve such a big problem; but its worh a shot.

 

I'm up in Canada and had the same problem,hadme stumped!finally was ready to try replacing heater valve when the guy at the parts counter told me they had never replaced one...Iwent back under the hood [Hell I didn't want to be the first to pay $600.for a valve!] anyway I found the facume line from the heater valve to the back of the engine manifold had come off .before you buy any parts check for vacume to the valve.might just be that easy.: