A/C Fan Switch Removal - '72 Charger SE

[Randy Layhe]

Hello all! This is my first post here though I've extensively used the search function in the past--great treasure trove of info!

I recently bought a '72 Charger SE 318 for my fiancee (she's always loved the idea of having an Americana Muscle Car). In trying to get her A/C working, the blower only seems to work on low speed. All wires to the blower resistor are testing positive for power per my test light. In fact they all illuminate the test light at varying degrees of brightness so I believe it to be good. The switch doesn't have a good ..."feel" to it so I'm thinking it is probably the culprit. Looking under the dash, it seems like it would be real bear to get the switch out of the car. Can anyone please advise here? I don't yet have a factory service manual.

Oh, and the car has factory A/C.

Thanks!

 

[Nacho-RT74]

Yes, low speed is the default speed even with lever fan switch unplugged. ( have you checked if MAYBE plug is disconected ? )


Two 3/8 nuts on sides and one 1/4 screw for an extra bracket. Will came out the full assembly.

Its tricky but doable

 

['68 Charger]

Here's a pic from a 1972 B Body dash from the backside view. The yellow arrows are pointing out the 3 mounting points for the A/C heater control unit. This is a standard cluster but the rallye cluster has the same mounting set-up.

 

[Randy Layhe]

Nacho, that's a good point. I'll confirm asap. It sounds somewhat common for the switches to go bad too from what I've read by searching.

68: very helpful! This is a very helpful forum already!

Thanks,
David

 

[Nacho-RT74]

Was searching a pic with a rear view but couldn't find it

The lever fan switch is a common failure on 73/74 but not sure on 71/72. Can't tell on 71/72 since switch is quite different and my car is 74, but on 73/74 the plug uses to get melt due the heat caused by the load switch drives through in mid and high speeds. This is because the plug conects straight to the switch and switch points are weak inside unable to hold the load. This causes heat up to the points inside, then the prongs, then the terminals and plastic plug. I upgraded my blower system with 6 relays, one to each speed... Low, mid, high, heater speed ( yes, heater is diff speed on A/C cars ) and... Can't recall the 6th relay use LOL... Will search for a diagram I made with whis upgrade. I think it was for the deff/vent speed, which is feeded straight from switch function selector and not from the lever switch, even drives the same high speed on A/C function

71/72 switches get attached a pigtail harness what carries the plug hanging around. Its in fact the one close to the rear screw to the bracket on pic. This makes the plug to be safe from the straight heat from switch itself, but, maybe the switch itself got shot already... Althought like I told you, MAYBE is simply unplugged

 

[Nacho-RT74]

This is the 71 wiring diagram. Same than 72 except the cavity used for the A/C compresor source on firewall bulkhead conector

And this is the realy Upgrade I made underdash... I have to correct my previous reply... Used 6 relays because I included low and high beams function on my relay upgrade all spread out underdash ( didn't want visible relays on engine bay and A/C system demands relays between switches and speeds resistor block so, is not posible to make it on engine bay ), but the A/C system just were 4... Heater, low, mid and high speeds.

 

[Nacho-RT74]

the heat at speeds switch was so high that was able to overheat the lever outside and you could feel it

 

[Nacho-RT74]

just noticed, the high speed relay it must be really feeded from lever fan switch, not the control unit like I did on diagram... but... you get the idea... The diagram I made on those days was referential.

I located the heaglights relays on back of kick panel, the Heater and high speeds relays around steering column, and heater and low speeds around glovebox area. No one of them is visible.

Didn't cut wires from original harness... just removed the wires from original plugs running them to relays and run a wire with same color between relay and original plug... will search a pic of that I took, for the heater and low speeds relays.

 

[Nacho-RT74]

I know you didn't ask for electrical upgrades, but, just in case... These pics are bad quality ( old nokia 6275 maybe 5 years ago ) but works to show...
Nothing here:

But pulling out the harness suddenlly appears:

which are hidden on back of glove box liner, hold by the A/C box bracket stud/nut, where also takes the ground for the relays.

Didn't cut any wire, just removed part of the tape and used same wire and terminal to trig on the relays... then run a wire same color from relay up to resistor block plug and taped it back together. That makes unnoticeable the upgrade under the dash.

Made the same in all relays systems

 

[Randy Layhe]

This is very helpful, thank you! I was just toying around with the car and it looks like the fan shuts off when the control box is switched to heat or defrost. Would this confirm the switch? Given the high heat right now I'm really not excited about getting to get the switch unit out of the car.

Thanks,

David

 

[Nacho-RT74]

Well, heat and defrost source to the blower comes from diff wire... The brown one and is feeded straight from control switch and doesn't go through the lever fan switch

 

[Randy Layhe]

Interesting...so I need to check my control switch. I know the cable isn't connected to the bracket anymore that moves the heater valve so hopefully I can fix that too while under there.

Thanks!

David

 

[Coronet 14]

If you remove the left A/C vent and lower the steering column the A/C controls will be alot easier to remove. The nuts will be easier to see. This will make them easier to remove.