| Author | Message | ||
     Brian Vogel Grand Master Username: guyslp Post Number: 820 Registered: 6-2009 |
Toward the end of this thread on SY2 wiper parking behavior the discussion turned to relays. I thought I'd break out this thread so that those searching for relay information, particularly regarding changeover (Single Pole Double Throw - SPDT) relays being used as On-Off relays (imitating the behavior of Single Pole Single Throw - SPST) in practice. I've been working around the right hand blower fan and now have the duct removed, exposing the three relays beneath. According to Chapter M in TSD4200, these three are the fan and compressor relay, fan delay relay, and servo isolation relay if you're looking at them from right to left standing beside the right fender/wing. The fan and compressor relay is your usual SPDT relay used as you'd expect it to be. The other two, though, are not. The fan delay relay, shown here:  has its C3 (normally closed - hot when relay coil is not energized) capped off. Given that this is the case, it's function is to be ON when energized and "doing nothing"/OFF when not. The servo isolation relay, shown here:  has its C1 (normally open - hot when relay coil is energized) capped off. Given that this is the case, it's function is to be "doing nothing"/OFF when energized and ON when not. This is, of course, the reverse of the behavior of the fan delay relay. I also got a very good look at just how corroded the connections can become on these things. Here are two photos of the Servo Isolation Relay once the connectors were removed. The female slides looked just as ugly as the male spade terminals.   I'm amazed this thing even functioned, but since the climate control was functioning just fine I presume it must have been. This scene simply reinforces my penchant to use electrically conductive grease on all connections when I put them back together to prevent this sort of mess from occurring in the future. Now I need to clean up the contacts on the Scintilla switch that's right next to these "while I'm there." Brian | ||
| Omar M. Shams Grand Master Username: omar Post Number: 395 Registered: 4-2009 |
Dear Brian, What purpose does the fan delay relay serve other than wait for the condensor and the heater to be at the correct temperature before allowing the fans to come on? If that is all it does, then frankly that is a nuisance for me in hot Dubai. I would sooner bypass it and have the fans blow air the minute the switch is activated. Thanks Omar | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 824 Registered: 6-2009 |
Omar, You're well beyond my knowledge on this but, based on the behavior of the climate control system during heating season here I'd say that's one of the purposes of that relay. I also wonder if it serves as a "fan cut-out" relay when cranking the car? Someone here will certainly know. Photos from today's work: Scintilla switch (or at least I think it's a switch) before:  and after cleaning:  . . . that bit of stuff you see around the connections is No-Ox-Id A-Special electrically conductive grease. And, the relays with labels (since it was much easier to position them out of order due to work by a previous custodian):  Brian |
