HVAC controls 74
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3rd Gear
Joined: Jul 2011
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HVAC controls 74
My heater controls, the fan to be specific, and possibly other things are not working. The fan does come on in one position but it is low so I believe that it would be a control problem and not the fan itself. I am going to fix the AC before the summer is out but surely need the rest of the system working properly. Any input would be appreciated.
Advanced
Joined: Jul 2007
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The first two things to check are: 1) There is a in-line fuse in a fuse holder located inside the engine compartment along the drivers side fender and 2) the fan relay which is a small chrome plated relay bolted to the side of the air conditioner box inside the engine compartment on the passenger side near the firewall. The relay's are very unreliable but can be disassembled and the points inside cleaned and made to work again. Replacement relays are readily available.
Le Mans Master
Joined: Aug 2006
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Does this help?
The 30 amp fuse controls the hi speed for the fan, if it's blown you only get low & medium speed.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Also note the 'resistor pack' [the square doo-hickey near the center of that schematic labled "RESISTOR"] which could be defective. It is mounted to the top side of the A/C-Heater plenum on the firewall and it is easily removed for testing and/or replacement.
