Hello everyone. I have a weird question with my 69 Firebird with a/C. When I first start my vehicle I could turn the air on through all speed even up to high but then after 30 seconds the high option quit working but all the other ones remain working. Is this a relay thing? I thought it might be so I went to replace the relay but noticed the relay that I have only has three spade connectors when I go online to purchase a new one all the ones down there have four spade connectors. So I have two questions number one is this really a really issue I’ll check both the relay and the resistors. And second do I have the correct relay or wiring or is this an aftermarket? I’m the second owner of the vehicle but I think the A/C is original.

Hello?

Well, since nobody seems to want to take a stab at it. I remember reading a long time ago that if you only had one speed for the blower fan the blower resistor on top of the HVAC suitcase (under the dash) was the blame. Perhaps yours is being affected by heat and is on it's way out.

Have you looked at the wiring diagram on the firstgensite. They have one specific for the AC system. Don't think it is the resisters because they get bypassed on High and 12V is put directly to the blower. If I had to guess I would say it is in the switch itself, but I would jumper around the switch to mimic Hi (e.g. jumper Brown to Black-Orange Stripe). If it continues to run (after 30 seconds), it is likely in the switch itself.

With the symptoms, I wonder if someone replaced the inline fuse with an automatic reset breaker?

On my 69, the inline fuse has given me some trouble. It is located above the intake manifold in front of the carburetor, and I sometimes have to take it apart to clean it from corrosion. This fuse is only used for the high fan speed so it doesn't affect the other fan speeds.
It might not be the same problem on your car, but it is easy to check, if you haven't done it already.

What's a little strange is that is how my 1967 Firebird (w/AC) is designed/wired. Namely, that the high speed comes from a separate fused link under the hood. What is weird is the 1969 is different at least the schematic shows it to be different. So I don't know what to say.

x2 My 68 /w A/C fan speed dd not work. I bought a new blower resistor ... problem solved

jump the resister with a separate wire I think its 2 prong

Salmon38, I’ll check it out. As of now I have all speeds but the high speed always stops working after about 30 seconds. I’ll check that resistor.

I have looked at the wiring and the resistor is bypassed for a direct 12v when on high. I’ll direct wire and see if I can isolate the switch. I have never worked on the switch but I imagine I will have to pull the dash. Any tricks to this as I assume it is a PITA.

Did your blower work in all speeds then stop after about 30 seconds? I am tracking that the resistor only comes into play on the lower speeds.

Do you have a pic? Previous owner pulled the 350HO and dropped a 400 in and rerouted a lot of the wiring.

I only have an old picture, but the fuse seems to be hidden behind the thermostat housing in the picture. It is the wire incircled in red I'm talking about, running from the alternator to the high speed relay (incircled in blue).

The air cleaner is from a GTO, so it is not correct for a Firebird.

Isn’t there a relay involved? The relay sends full current to the fan motor without going through the switch