This is the third HVAC rotary control switch I've replaced. Typically, it happens when the AC doesn't come on once in a while and jiggling the switch gets it going temporarily. Some people have also experienced fires from this type of switch.

Don't know why, but it seems to be a point of high resistance that periodically cooks itself to death.

Would it be possible to isolate the control switch from high current, by using relays? If so, would anyone have a recommended wiring layout?

 

This is the switch/**** to control the fan speed right? Does it always burn out when on a certain setting? I know the highest setting has its own relay while the lower 3 speeds also have their own relay.

 

No, the fan speed switch is the smaller rotary one on the left side of the unit. This larger switch is the one connected to the directional sliders controlling the AC volume and vents. Looks like a lot of juice goes through these connections, possibly fused for 20 amps.

How about it electronics guys -- any way to "beef" up this area to handle or isolate the current?

 

my stock one just started burning up, it was actually smoking pretty bad.

it started a few days ago i was using window defogging and went to turn it off and it kept on running.

maybe try a better brand. where did u get yours at?

 

Over the counter at GM, Delco-Remy.

Hope someone has some ideas how to fix this chronic problem!

 

Don't know what switch you're using, but on the wiring diagram for a 93 Camaro the compressor contacts in the control switch only sends a request signal to the ECM. Very small current. Might get by using a standard fog light relay in this circuit, pretty small windings in those and would draw minimal current.

 

The wiring diagram is fused for 25 amps, includes the heater circuit too. Would inserting a relay into the circuit isolate the switches from the high-amp requirement? Where would the relays be inserted?

 

delco one, thanks i need to try a new one at least, see what happens.

u have a part #?

i have had 3 thirdgens first time this has happened to me, my 91 was the first car i have deleted a/c, i doubt its from that. maybe from alot of use or pushing to hard on the slider.

 

I see these are different from the 93 that I was looking at. For sure you could use a standard relay to switch the compressor and save your control switch. Just use the power lead from your switch to engergize the relay coil with other coil terminal grounded, use the power feed to the switch for the relay contact input and the output to the compressor circuit.

 

TTT

 

Opps, I screwed up on the terminal numbers there. The relay coil is on terminals 85 and 86, so ground one and send current from the HVAC switch to the other. Terminal 30 is main power input and terminal 87 is a normally open energize to close for output power. Something like this:

 

Thanks to Tom3 for the revised, clear instructions for the attached diagram showing how to install a relay into the HVAC wiring to avoid burning-up AC control switches. Note I have not yet installed the relay, so cannot validate it's effectiveness.