Heater Core Bypass Valve / Blower Motor Switch questions

[derek]

This weekend we plan to start working on getting our A/C components installed. One thing we intend to do is the heater core shut off that is described in the documentation section. Ideally I would like to use the vacuum valve that Gary mentions there.

Gary, were you ever able to confirm that Four Seasons 74612 is the correct valve? This is what the documentation page says:

For a 2-port valve Ford's E4FZ 18495-A will work nicely as it it has ports that are arranged so it can be supported by the heater hoses, as shown to the right. It is for an 1984/85 Tempo/Topaz with a high capacity dual core heater. The previous info is apparently incorrect! I just bought a Four Seasons 74614, which is for an 84 or 85 Tempo or Topaz and should be the equivalent of an E4FZ 18495-A. As it turns out, this is a normally-closed valve and opens with vacuum, which is exactly the opposite of what you want. Instead, I think you want the Four Seasons 74612, which is what I've now ordered. More when I get it in and install it.

Additionally, if we are going to go that route, we would have to pull out the selector and while in there we want to address another issue we've noticed if possible:

Our blower motor stays on even when the function selector is switched to off. I'm assuming that it's something with the switch there, the vacuum functions all seem to work correctly, but my understanding is that when the selector is in off it should also be cutting power to the blower motor. Has anyone else run into this issue? I searched a while back and found some people talking about that behavior, but haven't run across a solution yet. I'm hoping cleaning it up a little may do something.

In the end I'm not hugely worried about the blower staying on all the time, as living in Louisiana there are very few times I'd be running the vehicle with it not running anyway, but it would still be nice to have working correctly.

[ArdWrknTrk]

Derek, I can't speak to the Ranger vacuum operated heater core bypass valve, but I can assure you that with the blower 'off' there should be no ground to the blower motor.
(It is ground side switched through the resistor block, giving you multiple speeds)

[derek]

ArdWrknTrk wrote

Derek, I can't speak to the Ranger vacuum operated heater core bypass valve, but I can assure you that with the blower 'off' there should be no ground to the blower motor.
(It is ground side switched through the resistor block, giving you multiple speeds)

Yeah we replaced the resistor and cleaned out the blower motor leaves a while back and that's got the different speeds working, it just never shuts off, so I'm thinking the other switch is just broken "on" somehow, hopefully it will be more obvious once we pull that thing out.

[Gary Lewis]

Derek - My bad as I hadn't updated that page.  It now reads:

​For a 2-port valve Four Season's 74612 will work nicely as it it has ports that are arranged so it can be supported by the heater hoses, as shown to the right.  (The Four Seasons 74614, which is for an 84 or 85 Tempo or Topaz and should be the equivalent of an E4FZ 18495-A, is a normally-closed valve and opens with vacuum, which is exactly the opposite of what you want.)

As for the blower switch, it doesn't have an off position.  You have to move the function lever to Off to turn the blower off.  The bottom position on the blower speed is just Low.

[derek]

Gary Lewis wrote

Derek - My bad as I hadn't updated that page.  It now reads:

​For a 2-port valve Four Season's 74612 will work nicely as it it has ports that are arranged so it can be supported by the heater hoses, as shown to the right.  (The Four Seasons 74614, which is for an 84 or 85 Tempo or Topaz and should be the equivalent of an E4FZ 18495-A, is a normally-closed valve and opens with vacuum, which is exactly the opposite of what you want.)

As for the blower switch, it doesn't have an off position.  You have to move the function lever to Off to turn the blower off.  The bottom position on the blower speed is just Low.

Thanks, I will get one of those ordered.  

As far as the blower motor, it’s blowing even with the function lever in Off.

[ArdWrknTrk]

Maybe you have a wire chafed through?
I'm looking at the diagrams and pin outs, and can't see how there's any ground with the function lever set 'off'...

[derek]

ArdWrknTrk wrote

Maybe you have a wire chafed through?
I'm looking at the diagrams and pin outs, and can't see how there's any ground with the function lever set 'off'...

Yeah after your post about that switch providing ground I realized it could be getting ground from a lot of places considering the condition of some of our wires... time to find it and trace it out I suppose

[Rusty_S85]

derek wrote

ArdWrknTrk wrote

Maybe you have a wire chafed through?
I'm looking at the diagrams and pin outs, and can't see how there's any ground with the function lever set 'off'...

Yeah after your post about that switch providing ground I realized it could be getting ground from a lot of places considering the condition of some of our wires... time to find it and trace it out I suppose

If you dont mind about the wire you can do a quick and dirty test.

Unplug wire at the HVAC switch see if you still have ground to rule the switch out.  after that the quick and dirty test would be to snip the wire about halfways between the HVAC switch and the blower motor.  If the motor turns off you know the short is between the midway point to the HVAC switch.  Can reconnect that wire and then go halfways between the cut and the HVAC switch and cut again.  Can repeat this process till you find the short to ground.

there are proper ways to test for this that doesnt require cutting but if the wire is already in bad condition and can be grounding out in multiple locations, sounds like the wire is trash and needs to be replaced.