Thanks to Terry, Denny, and Jack for helping me resolve the wiper door problem. Greatly appreciated. Now back to an A/C problem Jack helped me with awhile ago: locating and troubleshooting the relays mentioned in subject line. After several hundred dollars, a new updated POA valve, expansion valve, compressor, filter/drier and muffler line set, special oil and 134A conversion, my car now blows cold! Whew. The anti-dieseling relay works properly when mounted with the ground wire. I'm discovering how important ground wires/straps are on these old Vettes. But, I am missing the blower cut-out relay (the electric shop put in a jumper to get the a/c to fire) and I don't like the blast of air accompanied with shutting off the car. I have bought a relay but where the plug goes is different. The antidieseling relay looks like _-_ while the plug end for the blower relay looks like I_I .I don't know if this makes sense but the part that everybody sells is listed as a blower cutout relay....plugs dont match. Does anyone know whats going on here? Is the right relay available? Do I need these relays at all? Somebody has messed with these before and thats why the a/c had no juice. I have not had time to experiment with various combinations of not using the relay I have and/or the jumper wire. What an over-engineered mess.....A note on the wiper switch. Its supposed to be a grounding switch, well, it wasn't grounding, thats why my wipers wouldn't come on. I had to run a ground wire from the switch mounting screw to the firewall bulkhead to get them to work. GROUND WIRES ARE IMPORTANT on these cars! I'm close to getting the dash and console back together after all this so I can start prepping the car for paint. Which leads me to my next question. Do I need to gel-coat the car before primer? Starting a new thread for this. Thanks again everyone!
-
-
Re: C3 71 anti-dieseling and blower cut-out relay'
A typical reason for the wiper switch not to work is 'Bubba' failed to read the Chassis Service Manual when he tore into removing the cockpit center console.... The CSM has a clear note to the effect the bezel was designed to 'break away' in a head-on collision and has weak points that will fatigue fracture if you grab it at the top and try to pull/pop it free from the upper dash panel!
Once the center cluster bezel is fractured (MANY are!), you can lose the ground integrity of the wiper switch. But, everyone who's worked on these cars knows this history and its details...
Yep, the blocking relay was there on AC equipped cars to prevent the blower motor from 'surging' on during engine shut-down when the anti-diesel relay kicked in to over-ride the center console AC controls and FORCE the clutch on the A6 compressor to engage and add drag to the engine. Your copy of the '71 Chassis Service Manual will tell you there were exceptions to this in the Chevy lineup with Camaro NOT having this feature and mechanics/owners told to simply expect/live with the fan turning ON during engine shut down.
I believe both the anti-diesel and blocking relay are GM discontinued although a later GM part (6273301) WILL physically substitute for the factory original 3996203 anti-diesel relay. I'm not sure I'd be too concerned about the physical cosmetics of these relays as they mount to the RH side of the Harrison air box in the cockpit and are 'masked' from view by the RH lower dash panel....
And, YES, you have to physically connect the dash harness' discrete ground wire to the mounting bolt of the anti-diesel relay (AS depicted in the AIM) because the relay's case/bracket IS the relay's ground. In the Corvette application, both relays mount to the Harrison air box with is non-conductive fiberglass!!! Without the ground, the system won't work... The blocking relay takes its ground from the wiring harness connector.
Without a correct blocking relay, you'll have to live with the AC blower fan surging on during engine shut down AND expect to fail a PV and/or the Flight Operations Check if you pull a '71 savvy 'meanie' judge. BTW, I happen to know one!
Comment