fritz442

Hi folks, I know this topic has been beaten to death, but I have to ask. 72 Cutlass 350 w/AC, heater didn't blow at all. Replaced the relay by the brake booster and was getting a click. Found the inline fuse and replaced that, now I have high only. Whats next? Resistor? Is that another relay over by the blower motor, next to the big round emissions-looking thing. Thanks for any help!

1970cs

Here is the link to a 1970 heat/ac diagnostic flow chart should be the same system. page 1-18 manual
Link is to wildaboutcars.com free to join and use!!!!
http://wildaboutcarsonline.com/membe..._Section_1.pdf

Pat

MDchanic

Yup.

So far so good - looks like you're doing the right stuff.

So the high position on the switch, the high-speed relay, the high-speed fuse, the general heater blower fuse, the blower motor, and all of the associated wiring and connections are good.

Yup, or the resistor plug, or wiring that goes to it, or the low-speed terminals of the switch, or the low-speed terminals of the relay.

Resistor's the most likely, though.
Is it connected?
It's easy enough to take it out and take a look at it.

Well, I'm not sure what round thing you're talking about, but in '72 some A/C cars had low-temperature relays, and some had rear defogger relays.

- Eric

jaunty75

This is the classic symptom of a failed blower motor resistor. Replacing that is your next step.

fritz442

Thanks guys, I think I'm getting close then. So where exactly is the resistor? Under the hood or dash?

jaunty75

The 1972 Chassis Service Manual, available for free at wildaboutcars.com, shows the resistor to be mounted on the heater case up under the dash behind the glovebox. The manual says to disconnect the wiring harness from it and remove the two screws that hold it on.

If you do go look for the manual, it's figure Figure 1-27 on page 1-17.

Rickman48

Over the years, I've had this problem, and usually found the harness plug melted at the resistor. I was lucky enough to repair it to work.
Only once did I have to replace a burned-out assembly, and was lucky enough to find a used one.

MDchanic

Sorry, Jaunty, not to bust your chops, but he's got A/C (or we wouldn't be having the "only works on High" discussion), and you're looking at the "heat-only" diagram.

On A/C cars it's right out in the open on the evaporator box, under the hood, as seen here:



Takes all of about 60 seconds to replace it.

- Eric

MDchanic

I agree that that's a strong possibility, which is why I didn't pin myself down to the resistor being the only part of the circuit that could be bad.

If it's just the plug, the spade connectors can usually be removed from it individually and cleaned up, and if worse comes to worst, they can be replaced with ordinary ¼" spade females and used without the plastic plug assembly.

- Eric

fritz442

Thanks everyone! Got Patriots today, I'll check it out this week hopefully that'll do it!
Ed