rodrieguz

ok I admit I'm green when it comes to these cars but I still love em'

My ac control panel is not working, I assume there is a relay or fuse somewhere. Please help me locate it. On the 68 coupe

MDchanic

Look for 20A fuse in panel under dash by emergency brake, probably top left, labeled "Heat A/C."

Also, got any more details about your symptoms?

- Eric

rodrieguz

heat does not blow when you turn the switch from the dash on. My dad hooked a hot wire directly to the blower motor switch connector (left side of engine bay firewall) and it started blowing inside the car.

MDchanic

Does the heat blow ONLY when you hook up a hot wire, or does it ALSO blow when you turn on the switch? And if so, what switch, and what setting(s)?
And what terminal (wire color) did your father connect the hot wire to?

rodrieguz

pretty sure it was the black one, on the far left closset to the pass fender.

when the terminal was charged the heater started blowing then.

Lady72nRob71

With ignition switch in RUN, measure voltage to ground across each side of the fuse, or use a test light. Let me know what you get. Either the fuse, connectors, fan switch, or even ignition switch could be bad.

This is assuming you have heater without factory AC... I do not have the AC schematic in front of me but the circuit should be similar (except for high speed fan).

Rickman48

He did say A/C control at the begining.
On the top of the A/C box you should find a 4-wire plug that goes to a oval/rectangular piece with 2 - 5/16 bolts to it. I really don't know what it is, but I've cleaned/replaced it on a '69 442 to get the fan to work.
First time, the plug was melted together, and I was lucky enough to find one, second time, I replaced it from a yard. Never another problem!

Lady72nRob71

I have helped troubleshoot someone elses circuit that was called 'heater controls' but turned out to be AC ones. We wasted lots of time for just a blown high speed fuse...
Don't want to go that route again - have to confirm to be sure we are both on the same page.

MDchanic

I agree.

We still have very little definite information.

MDchanic

Specifically, we know:

1. Presumably means the fan switch doesn't turn the fan on, and
2. that this is an A/C car (not a heat-only car).

3. Presumably refers to: "1968 cutlass "s" 2-dr hardtop" in his sig.

4. This contradicts assumption number 1.

5. Does this mean the resistor block on the plenum, the high fan relay, or some other plug?

6. Could be the resistor block, but this isn't where you'd connect a jumper (the brown wire at the heat relay is the hot on an A/C car), also, without checking the diagram, I believe there's no Black wire, but there is a Black with White stripe.

It will be easier to help this member when these questions are answered more clearly.

- Eric

rodrieguz

Thank you guys for your time,
Maybe this will help you guys help me,
this car has factory ac/heat. please excuase me if i'm not explaining what's going on correctly..........I turn the car on engine running, go to turn on the heat from the control panel on the dash right of steering column left of ignition key, nothing happens, nothing blows out. I take the car to my dad to have a look, he tells me the conrol panel on the dash is bad, he hooks up a wire from the battery to the big black box (with the ac lines comming out of it to the left of engine bay ) it has a 3 pin connector on top with a single connector right below it. the wire was hooked up to the top far left terminal, he tells me I can run a hot wire off any terminal to a new switch, bypassing the factory contoller. that's not what I want to do I'd rather get this working correctly.
the fuse is good, checked both sides with a test light.

rodrieguz

ok I tried this, took the little plug out and it had wire coils behind it, took a wire brush cleaned and reinstalled, checked blower motor and it worked.
Should I remove the resister again and clean it with a wire wheel on a bench grinder? It looks so delicate I'd hate to brake a discontinued part

MDchanic

NO. Do not do that. Those are the fan speed resistors. If you break them, you will have to replace them. If one or more is broken already, then that's your problem. Any auto parts store should be able to get that resistor block.

Here is a copy of the schematic of the electrical system with A/C.
This is for a 1973, so you can ignore the Low Range Relay, Engine Thermal Switch, Ambient Switch, Thermal Limiter, and SuperHeat Switch - you don't have those. I have a clearer scan, but the BBS will not allow me to upload it. I can email it to you if you'd like.

Simply follow the electricity from the ignition switch to ground. Print it out and you can go over it with a highlighter if you need to understand it.

Somewhere in there, you have a bad connection.
It sounds like your father connected a hot wire to the Black / White Stripe wire going from the resistor block to the high fan relay, so you know everything after that seems to be good, so you can concentrate on the parts before that. Just follow along the circuit with a meter or a test light, and when you have no power, you've found your problem.

No fan at all would suggest a break in the circuit of the orange and black wire from the ignition switch to the 20A fuse (but you said the fuse had power, so that's got to be good, right?), or the brown wire from the 20A fuse to the fan switch. After the fan switch, there are a number of different wires, so at least one speed would work if one wire were bad.

Just go down the line until you fond the problem, and clean the terminals as you go.

Good luck.

- Eric

Lady72nRob71

So all is working now? If so, then you most likely had a dirty / corroded contact. Being in the engine bay, it can happen. If the problem resurfaces, the contacts inside the wiring plug might need to be cleaned and crimped down a little, meaning each one would need to be removed from the plastic connector, which can be done by releasing them with a tiny jewelers screwdriver. A wirewheel on a dremel works good here.

The resistor itself should only be cleaned by hand. Electric tools may easily damage it. The contacts could be polished with a dremel wirewheel though.

rodrieguz

thank all you guys for your imput on this matter and the wiring diagrahm.
I drove the car last night for a few hours with th blower constantly blowing good heat. On to the next issue....

Lady72nRob71

Great - one down, ?? to go!