My 71 chassis manual wiring diagram shows this, but I've searched far and wide without finding anyone selling heater resistors for these cars. This isn't the same as the resistor that screws into the face of the AC box on the firewall, is it?
The resistor array allows three values in ohms to be put in series in the circuit resulting in voltage drops that give you three blower fan speeds.
That being said Dennis, yes it's usually a small group of resistance coils set into a phenolic base with a couple of screws somewhere in the heater box. On the opposite side of the base are the male spade terminals that attach to a wiring harness connector. Devon
http://www.ebay.com/itm/Nos-1971-72...ies&hash=item5626eb5a2e&vxp=mtr#ht_500wt_1316 Not sure if this is the one you need, but at least it is a buick and a 71.
Yes, it is the same. I was confused too, because the manual shows the resistor as being mounted on top of the air plenum under the dashboard, on the passenger side. I searched high and low before I realized that it was in the engine compartment.
NON Ac cars are under the dash. AC cars are in the engine compartment on the fiberglass box. Look for the wire plug. The connectors are often different for each year. Get the one for your year or it will not connect to the plug.
Thanks to everybody for their input. I actually have the resistor that's like the one in the pic posted by Lee. If the resistor is faulty, would the blower motor not run at all, or just not run on three speeds? Also, does anybody know a source for new ones?
When they go bad you usually end up with "off" and "hi" as your options. Sometimes you just end up with "off". When you look for a replacement call it a "blower motor resistor" and you'll have better luck finding it.
I picked up a spare one when I thought mine was going out. Turned out it was the connector which was dirty. When they go (i.e. one end burns out), you lose one or more of your fan speeds.
I've got nothing on any fan speed. The blower motor is new, so I'll try cleaning the contacts. If that doesn't work it's off in search of a new resistor.
If it looks like the one in the pic. In my experience the only way they can go bad is to actually be broken somewhere on the coils.
Just use a regular Volt Ohm meter. Set on resistance. You will notice different Ohm readings between the terminals. Or, just ensure there is continuity between each of the terminals.. 1 and 2, 1 and 3, 2 and 3
These resistors are built like tanks - if they have not broken, snapped a wire, they are still good. You can test them with an ohm-meter if you are curious.
Bingo. That was the problem with the blower not running. However, now it only runs at one speed from Lo to Max. I checked the resister with an ohm meter and it appears to be good. Both the relay and the fan switch are new, but I tried another relay with the same result. I'm wondering what else I could check before pulling the dash and trying another switch.
If it's not the resistor, and not the relay or switches, then it must be something in between. Get a meter and ohm out each wire between the switch/relay and resistor contacts until you find out what's wrong. Just check the wiring diagram and find out what's open or shorted.
