Heating Works Only On Max-heat

[mohitlad]

I have a 1992 SC 400.

Had it for a year with about 105k miles on it.

Since last week, the heating does not work. Ran a diagnostics, and came up with code 21.

Funny thing is that the heating works only when I turn the knob to MAX_HEAT. Even one unit below that will blow cold air.

Any suggestions on what to do would be helpful.

Thanks

Mohit

[Marty Witt]

I have a 1992 SC 400.

Had it for a year with about 105k miles on it.

Since last week, the heating does not work. Ran a diagnostics, and came up with code 21.

Funny thing is that the heating works only when I turn the knob to MAX_HEAT. Even one unit below that will blow cold air.

Any suggestions on what to do would be helpful.

Thanks

Mohit

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Code 21 is the solar sensor and most likely means it was dark when you ran the test. My car did not blow heat also. I found that by adding a little coolant to the system (even though it appeared full) made my problem go away. It's real easy to try it.

[AppleJack]

I've got the same car - same year .. and have had that same problem .. sorry to say I don't have a solution for you. Mine seems to be intermittent and actually hasn't had that problem for a while ... I checked the coolant level to make sure that wasn't related. Good luck and I'll stay tuned to the responses you get ...

[mohitlad]

I've got the same car - same year .. and have had that same problem .. sorry to say I don't have a solution for you.  Mine seems to be intermittent and actually hasn't had that problem for a while ... I checked the coolant level to make sure that wasn't related.  Good luck and I'll stay tuned to the responses you get ...

←

Ok, thanks for the tips. adding coolant seems to do the trick. I am not sure if the air is as hot as it should be, but it is definitely warm.

Thanks

Mohit