Dash HVAC Relays

[RoadTrippin]

Trying to do some clean up work from PO's. I'm not quite sure why these switches were added to the dash hvac circuit. Looks like an extra relay was added as well. Both of the inside switches need to be on before the dash controls will work. I want to get things back to normal but I'm not sure what the stock wiring configuration looked like. The trailer wiring that was used inside, runs right in front of the blower. Anyone have any pictures of the relays with unmolested wiring?

Thanks!

 

[Christo]

Trying to do some clean up work from PO's. I'm not quite sure why these switches were added to the dash hvac circuit. Looks like an extra relay was added as well. Both of the inside switches need to be on before the dash controls will work. I want to get things back to normal but I'm not sure what the stock wiring configuration looked like. The trailer wiring that was used inside, runs right in front of the blower. Anyone have any pictures of the relays with unmolested wiring?

Thanks!

View attachment 3768

View attachment 3769

View attachment 3771

Wiring diagrams are available at bdub.net.

 

[1978budbus]

I think these are artifacts of an enhancement that the previous owner(s) may have removed (like additional fans). My 78 Transmode Royale has the two firewall mounted relays but does not have the one mounted to the blower motor, I do not have the thermal overload at the green tie wrap. I think a couple of hours with a VOM and a set of prints will answer a lot of questions.

 

[RoadTrippin]

I found my copy of the service manual schematic. Yeah, I'll just rip out what was added, test the original connections and go from there.

 

[Matt Colie]

Brian,
Document what you rip out, it may have served a purpose you haven't recognized yet.
Matt

 

[RoadTrippin]

Brian,
Document what you rip out, it may have served a purpose you haven't recognized yet.
Matt

For sure. Working on installing a small accessory fuse panel today and ID'ed the green fusible link. Also may just replace the big relay since its looking pretty crusty and delete the delay relay once I get the wiring sorted.

 

[Scotty]

Im working on my HVAC (transmode - 78 Royale) and have the Delay Relay as well
my issue is corroded plugs/connectors

does anyone know where one can obtain the plugs for the delay relay as well as the blower relay?

 

[Christo]

Im working on my HVAC (transmode - 78 Royale) and have the Delay Relay as well
my issue is corroded plugs/connectors

does anyone know where one can obtain the plugs for the delay relay as well as the blower relay?

@1978budbus asked me to "relay" the following connector info to you: 3 terminal connector, Rock Auto WVE Part number 1P1010 and the 2 terminal is Standard S85.

BTW, today I just happened to order a new blower relay from NAPA. It's an Echlin AR109.

 

[Scotty]

thanks @1978budbus and Christo
but the Delay Relay on my rig is a 4 wire (pic attached)
that connector does however work for the Blower Relay connector of which I need as well - awesome

Christo - if I interpreted the parts interchange on GMCMI correctly - the AR109 is for the 'blower relay', not the 'blower delay relay'
did I get this incorrect?

 

[Christo]

thanks @1978budbus and Christo
but the Delay Relay on my rig is a 4 wire (pic attached)
that connector does however work for the Blower Relay connector of which I need as well - awesome

Christo - if I interpreted the parts interchange on GMCMI correctly - the AR109 is for the 'blower relay', not the 'blower delay relay'
did I get this incorrect?

You're exactly right; I have corrected my post. Here's a handy diagram I made a while back:

 

[ktcnyc]

You're exactly right; I have corrected my post. Here's a handy diagram I made a while back:
View attachment 4615

 

[ktcnyc]

Still getting to know this stuff -trying to get low and mid speeds to work on my blower...so- what does the blower delay relay do?

 

[Scotty]

Still getting to know this stuff -trying to get low and mid speeds to work on my blower...so- what does the blower delay relay do?

delays the blower (for several seconds) from engaging max speed, this is to give all pneumatic doors time to completely open or close so they don't get interrupted by the stronger air flow generated by the fan at max speed.
or something like that

 

[RF_Burns]

You're exactly right; I have corrected my post. Here's a handy diagram I made a while back:
View attachment 4615

Christo,
On this diagram, the relay you have labeled "Headlight Relay", is actually the Horn relay. It also has the main power terminal which the main fusible link is attached (bolt terminal). At least on my '77 xPB coach it is.

 

[Christo]

Christo,
On this diagram, the relay you have labeled "Headlight Relay", is actually the Horn relay. It also has the main power terminal which the main fusible link is attached (bolt terminal). At least on my '77 xPB coach it is.

Thanks, fixed.

 

[RoadTrippin]

Bringing this one back to the top. Finally removed the PO's wiring mods to try and get back to a stock wiring configuration to see what works and what doesnt.

Comparing my wiring colors to the wiring diagram:

-My Yellow off the delay relay and connects to Purple to the Blower relay. (I removed his yellow splice which ran into the cab to PO added switches)

-Removed relay on the blower motor and additional wiring that ran to cab switches. PO Green wire on the add-on relay connected to brown on the original delay relay. I imagine that I splice Brown off the delay relay to the rest of the brown wire thats connected to the blower motor? (im holding the brown wire together)

Just trying to get a sanity check here to see if I'm looking at this right before I put any power into these wires.