The dash pad has been removed along with most everything that could be unbolted. The annoying key chime is on the back of the column . The horn relay is on the radiator support on the driver side .
Went over the area under the dash no relays except for the buzzer ; took some pictures of under dash but no relays . If I work under the pretense I do not have a relay , where is the next most likely area that’s problematic
Where the wires go through the firewall? Check there for wire damage. Turn the fan on and move the wires around, see if there is an internal break somewhere.
Moved around the wires coming through the firewall ; with fan running at max there was no noticeable difference. Unwrapped the tape around them not that it tells you anything the wires look untouched and in good shape
No, that's not what I meant. Position your fan switch on one of the positions that DON'T work. Then start moving wires around and see if you get any fan action. If your switch is good, and your resistor array is good, the only thing left is wiring or connections.
Tried moving the wires in the non functional positions with no results . I tested both switches previously but tried bypassing the switch all together by touching the brown wire to the remaining wires w/ the key on . The black/orange wire was the only wire that got the fan on ( max ) . Nothing from remaining wires. If I’m not missing anything then like you said the problem is in the wires under the dash. These wires look to be wrapped up for 50 yrs or so and I think I eliminated any other causes
Took a break and went back to this enigma again and found something that doesn’t make sense . Unwrapped the wires under the hood going to the resistor and followed them through the grommet and now I’m not even sure what I’m looking at . The black/ orange , blue, and yellow go to a 3 way plug doesn’t look like it has been plugged in a while . In the bundle is also the green wire for the a/c clutch , that along with the brown wire into a 2-way plug . The plug goes into the heater control unit ( this much I knew ) . The wires that were plugged into the fan switch go into the main harness and I’m guessing through the the bulkhead connector. Only way to trace them back is to drop the column ( ugh ). The only wire that appears to go through the bulkhead connector is the orange/ black as it shows on the chassis schematic . Had the car out in the sun for a change and took some Picts of the harness & plugs. Almost at the point of raising the white flag and calling in re-enforcements. May not be that easy in this Coronavirus time we live in.
My resistor assembly has a plug so you can't mess up the wiring. No such luck there with yours. Either try to trace back all the wiring, or just buy a new engine harness. That looks like a PO's Cluster-_____.
Having recently gone through this nightmare, let me shed some light. I have a '68 GS400 w/factory air. I can confirm that they did not use relays in our '68's. I replaced my blower motor (Delco made in Canada), resistor (from the Parts Place), still didn't have all speeds. It wasn't until I purchased a NOS '68 blower switch off ebay that I got all blower speeds to work. I'm highly suspect that your switch has issues. Funny thing is that I took the old switch apart and it was hard to see what made it fail short of dirty 50 year old grease. If your wiring checks out ok, then your only components are the switch, resistor, and blower motor. FYI, Buick64203 is showing you the correct wiring diagram for your car. I have a FSM verifying this. You should also have a ground strap from the back of the block to the firewall from the factory, and the blower motor is grounded from one of the screws that attaches its mounting hole and the other end attaches to either the firewall or other suitable grounding place. I went through hell with this for months. Best of luck, hope this helps! Dave
Update- Positive news now have medium, high, and maximum working . I had a couple of issues from a slightly corroded terminal on the bulkhead connector, the 3 wire plug coming from the resistor had 2/3 terminals corroded and broken . The ground plug on the inner fender was loose as well. the resistor plug that feeds into the main harness was buried inside the harness and cocooned in tape for god knows why . Going forward still want that low speed to work. More details to come
As I said In mast post in have 3 out of 4 speeds working but I still want that low speed setting on the fan to work . Two thoughts; I was reading some threads where the low speed oN GM cars will not work believe a certain outside temp . Do I have onc of these on 68 Skylark convertible ? Secondly while I have med, high, and max settings, they are out of sequence when they turn on . Most switches start with OFF on the bottom setting and MAXIMUM SETTING on top .. I have working OFF- OFF , LOW- Nothing , MEDIUM- HIGH , HIGH - MAXIMUM, and Maximum-HIGH . The 4 wires on the resistor ( with a new resistor)are as the FSM schematic ‘s are correctly connected to the the correct wires . The 5 wires on the plug are likewise connected to the correct 5 wires ( diagram in photos ) Any thoughts on diagnostics to get the fan speeds in the correct sequence ?
