I recently purchased 77 300d. It hasn't seen a lot of use, just 51000mls but I have some climate control problems. I know the heater is designed not to work until the engine is heated up with the exception that the defrost overrides the temperature sensor.
The heater will not blow under any condition, even with the car warmed up unless the defrost button is first activated. The heater will then operate. It will continue to be operational even if I turn the car off until the point that the engine cools all the way down again at which point the defrost will have to be pushed first again. The heater will also not turn off once it is activated until the engine cools down again. The off button just seems to have no effect.
I'm assuming this is some problem with the temperature sensing device but I am not sure. Where is the sensing device and how difficult is it to replace? Does anyone have any other ideas about what may be malfunctioning?

Kerry,

I have a 1977 300D as well. It is a great car.....bullteproof, with the exception of the climate control.

There are numerous failure points in the ACC system, servo, pushbutton control unit, vacuum actuators, etc.

I received some great diagnostic information from Larry Bible that I would be happy to fax to you. It helped me narrow down similar problems that I had with my ACC system.

Just post your fax # or send me a private message with your fax # and I'll send it over. Or do same with your address and I'll send via snail mail

JCD

I also have a diagnostic flow chart for problems with the servo-type climate control system. Can't say how it compares to Larry's info, but this is a good diagnostic chart that I used to help me cure my problem. I'm sure Larry's diagnostic info is good, the one I have is from a professional service manual. Let me know if you want it and I'll mail you a copy.

Good Luck!
Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.

JCD and Tom:
Thanks for replying. I am really enjoying the car except for this minor problem. In an ideal world I would like a more direct manual type heating/ac system. I would appreciate copies of both. My fax is 303-989-6285. Please put my name on the sheet since the fax is at school where a lot of people receive faxes.
My address is:
Kerry Edwards
117 W. Irvington Place
Denver, CO 80223

Kerry

Sent the climate control diagnostic info, 7:21AM EST.

Good Luck,

JCD

I have a 1980 300SD turbo with the same climate control problem. Do these diagnostics flow manuals apply to this model also? I have all buttons working but no heat whatsoever. I think the control valve is not opening. I bypassed it altogether and get all heat now but no air con.I would appreciate any info to help me trouble shoot further. Thanks

Kerry:

I mailed the AC diagnostic flow chart yesterday.

Cabazon:

You should have the AC using the servo to control the automatic climate control (TXBill has an SD like yours and it has the servo). These are complicated systems and several things could cause your problem. The only way to know is to do a check of the system. Send me your address and I'll send you the diagnostic flow chart.

Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.

Same here, send me address or fax number and I'll get it to you. Tcane is exactly right, the complexity of these systems makes a structured approach necessary.

JCD:

Was that you bidding on the sun visors on eBay yesterday? If so, did you win them? Hope you won because they looked like they were in good condition and the right color. I was going to go to the junk yard soon for some parts and was going to look for visors for you, but won't if you won.

Is the diagnostic info you have from Larry a flow chart or pages of printed info?

Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.

Thanks a million tcane and jcd I have Emailed you my fax and address

Here's another tip. As you work thru the diagnostic, take good notes. It is important to follow the structured approach, document what happens on a notepad and review the notes carefully before jumping to any conclusions or changing anything.

Good Luck

JCD