Protecting your blower motor switch (non-EATC)

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Protecting your blower motor switch (non-EATC)

Reply #30 – August 14, 2012, 07:50:56 PM

I looked over my layout and you are correct, man what an oversight on my part,, when hi is selected we get "LOW"

I looked back at your layout and bounced it off the explorer page you posted.
I believe you have a problem with your layout in that the relay should clatter all the time when high is selected.
When hi is switched on, its wire delivers power out to the coil of your relay and then the relay see's ground potential. At this point it switches the contacts poistions and thus removes power delivery to the coil,,,, this process should repeat itslef and you would hear a clatter.
See what i mean?

For the past couple days off and on i have not been able to nail a "bypass on HI" relay mod because that stinking ckt 261 keepts screwing me over.
IF "LOW" were ommitted from the layout (ckt 261) then my version would work. Low is nice to have but sometimes low is "too low" for my winter time tastes.

what say you ?

Protecting your blower motor switch (non-EATC)

Reply #31 – August 15, 2012, 10:39:21 PM

Ugh. You're right. Would this solve the problem?

Edit: never mind. I don't think this would work either. The ground would still bypass the blower motor switch. Any upstream ground would. I need to think about this some more.

Protecting your blower motor switch (non-EATC)

Reply #32 – August 15, 2012, 11:15:45 PM

Okay, maybe this one...it basically follows the Explorer method by reversing the current through the switch and the resistor pack. I think I've convinced myself that the only way this can work is to have the relay upstream of the Hi setting.

EDIT: Another light in my brain flickered on (albeit dimly). You also have to swap the pins on the connector to the blower resistor to get the fan speeds right. revised diagram below...

EDIT #2: Revised the terminal pinout diagram in the small box in the lower right.

EDIT #3: Minor cosmetic cleaning up (no circuit changes).

EDIT #4: Unswapped M1 and M2 pins on the resistor pack (good catch, Crazy88).

Protecting your blower motor switch (non-EATC)

Reply #33 – August 16, 2012, 12:55:42 AM

Welp,,, you nailed it, hats off to you. I didnt know we were allowed to repin things,,,just kidding and its likely one solution.
I bet you put a lot of work into the above recent adjustment, my head just about split dealing with a solution.

However, i have a new idea that just hit me and it appears you and i are "over here" when we should be "over there"

what i mean is if we copy cat the explorer version, it actually (and successfully) manages heat / watts most correctly.
You may not have noticed but on the explorer laout, the rotary switch is down stream of the speed resistor bank.

In our drawing we've been muddling through, our speed switch is upstream of the resistor bank.
In effect, there is still a sensible heat gain in the switch on all speeds except high because you have managed to place this contact on the direct ground leg. GREAT WORK!

I paid really close attention to post 21 by Crazy88 because in his comments, and intent, he said exactly what we both know needs done.

I would suggest we position the speed switch downstream of the resistor bank and effectively using this switch to select the respective resistor bank tap off point and control the ground only.
when high is selected, the motor can gain its own ground on a separate bonding point as per the oem Explorer design.

I am regrouping now, but with my schedule, i bet you will beat me to it.
thanks for helping me with this, Im not perfect by no measure.

Protecting your blower motor switch (non-EATC)

Reply #34 – August 16, 2012, 02:48:48 AM

ok,,
i think this might be the one, wire as shown, swap two connections at the dash, this way you dont have to fiddle with the resistor bank connector.
Puts selector switch on a ground source potential only.

lets review...........everyone put eyes on it.

Protecting your blower motor switch (non-EATC)

Reply #35 – August 16, 2012, 03:59:15 AM

Um, No. This revision has couple of problems and I have them listed in no particular order.

As diagramed, applying ground through the blower switch on both M1 and M2 positions, bypasses the thermal limiter and at least a portion of the resistor pack, which will increase current through the blower switch in both these positions.
With the blower switch in the high position AND applying ground through the blower switch, the secondary relay will either never energize, due to some lower source voltage (as measured at the top of the resister pack/bottom of the blower motor) or if it does energize, it will constantly cycle (chatter) due to the loss of voltage, since its voltage source is the same as the ground being applied to the bottom of the blower motor.
The new fuse (30A) inline with the resister pack is redundant as the circuit is already fused (30A) upstream of the blower motor and it's feed through the relay.

The only way to completely protect the blower switch, which would be overkill in my opinion, would be to use three relays, one each for M1, M2 and High, used to pass grounds appropriately to the resistor pack (M1/M2) and bypassing it completely as the current revision does. As Tom pointed out earlier, we sometimes tend to over complicate things unnecessarily.

The source voltage for the secondary relay(s) should be the switched side of the heater function selector relay.

The best solution, thus far, would seem to be Quietleaf's last revision, but would need pins 4 & 6 his blower switch diagram switched for the blower switch to operate as I believe he intends, e.g. the M1 position resulting in a lower blower speed (more resistance) than the M2 position (less resistance).

I should make it clear that the switch current doesn't care whether or not the switch is switching ground or source voltage. The current draw through the circuit and thus the switch is all that matters.

One final thought before I move on, is that with the heater function selector switch now only providing switched power to the heater function relay, is it really necessary or even desirable to fuse it with a 5 amp fuse? What is the current draw on that relay and does that same fuse provide power to another circuit on on this diagram?

Protecting your blower motor switch (non-EATC)

Reply #36 – August 16, 2012, 09:21:24 AM

the 15A fuse is back as shown , good point.

I really dont know what to make of the rest of what you shared. Current takes the path of least resistance.

why dont you trace out power and show me were this is wrong.
It mirrors the explorer layout. Ford did the same job with 2 relays and so can we.

Protecting your blower motor switch (non-EATC)

Reply #37 – August 16, 2012, 09:24:36 AM

i am surprised you didnt notice "why" i put the inline fuse down stream of K2.

Protecting your blower motor switch (non-EATC)

Reply #38 – August 16, 2012, 02:21:25 PM

Quote from: jcassity;396100

the 15A fuse is back as shown , good point.

I really dont know what to make of the rest of what you shared. Current takes the path of least resistance.

why dont you trace out power and show me were this is wrong.
It mirrors the explorer layout. Ford did the same job with 2 relays and so can we.

I am well versed in both whole flow and electron flow theories. As an ET in the US Navy, I have repaired and replaced more fuses, switches, wiring and other circuitry than I care to remember. Therefore, my understanding goes well beyond that of the typical shadetree mechanic and certainly beyond "path of least resistance".

Apparently, you have made some changes to your diagram subsequent to my last post, so it would appear that you came to understand my main points.

Yes, I agree that Ford did an adequate job of protecting the switch in the Explorer with only two relays, which is why I said that total protection using three relays was overkill in this application.

Lastly, tracing source voltage in the top half of the diagram, your primary relay, which I will call K1 and the "Heater Function Selector Switch" are now being protected by a 15 amp fuse instead of a 5 amp fuse, which I will refer to as F1. I have no idea of why you went back to a 15A fuse in this circuit, unless this fuse also protects other circuits not shown on this diagram. However, as it is currently diagramed, and without anything to indicate otherwise, the 15 A fuse now only protects the "Heater Function Selector Switch and K1, which should as diagrammed only draw milliamps, just enough current to energize the relay K1. Therefore 15A is far too large a fuse for this circuit, as diagramed.

Source voltage on your secondary circuit, protected by a secondary fuse hereafter referred to as F2, flows through K1 and stops at the blower motor and the switched power side of your secondary relay, which I will call K2. If the blower motor shorts, it "could" cause damage to the blower switch before the F2 opens to protect the circuit.

Quote from: jcassity;396101

i am surprised you didnt notice "why" i put the inline fuse down stream of K2.

Maybe my eyes are not fully awake yet, but I failed to find a K2 label, but the moment, I'll make the assumption that it is your secondary relay. I still fail to see why the third fuse, which I will refer to as F3, is necessary or would open any faster than F2. Perhaps you can explain your reasoning and why even Ford didn't need the third fuse to protect the circuit.

Protecting your blower motor switch (non-EATC)

Reply #39 – August 16, 2012, 06:33:17 PM

Good catch on my M1 and M2 pins. I unswapped them and revised my last diagram.

EDIT: never mind my comments about the fan speeds; they're the same... (smacks head).

Protecting your blower motor switch (non-EATC)

Reply #40 – August 16, 2012, 11:44:35 PM

Quote from: Crazy88;396113

I am well versed in both whole flow and electron flow theories. As an ET in the US Navy, I have repaired and replaced more fuses, switches, wiring and other circuitry than I care to remember. Therefore, my understanding goes well beyond that of the typical shadetree mechanic and certainly beyond "path of least resistance".

Apparently, you have made some changes to your diagram subsequent to my last post, so it would appear that you came to understand my main points.

Yes, I agree that Ford did an adequate job of protecting the switch in the Explorer with only two relays, which is why I said that total protection using three relays was overkill in this application.

Lastly, tracing source voltage in the top half of the diagram, your primary relay, which I will call K1 and the "Heater Function Selector Switch" are now being protected by a 15 amp fuse instead of a 5 amp fuse, which I will refer to as F1. I have no idea of why you went back to a 15A fuse in this circuit, unless this fuse also protects other circuits not shown on this diagram. However, as it is currently diagramed, and without anything to indicate otherwise, the 15 A fuse now only protects the "Heater Function Selector Switch and K1, which should as diagrammed only draw milliamps, just enough current to energize the relay K1. Therefore 15A is far too large a fuse for this circuit, as diagramed.

Source voltage on your secondary circuit, protected by a secondary fuse hereafter referred to as F2, flows through K1 and stops at the blower motor and the switched power side of your secondary relay, which I will call K2. If the blower motor shorts, it "could" cause damage to the blower switch before the F2 opens to protect the circuit.

Maybe my eyes are not fully awake yet, but I failed to find a K2 label, but the moment, I'll make the assumption that it is your secondary relay. I still fail to see why the third fuse, which I will refer to as F3, is necessary or would open any faster than F2. Perhaps you can explain your reasoning and why even Ford didn't need the third fuse to protect the circuit.

its all your fault

, your earlier post i refered to was bugging be because you were dead right.
You were an ET and i was an AT in the navy, so that makes sense you have a lot to offer here.

here is what i did in the wee hours, i jumped on this adjustment because i seem to be able to clearly think in the early hours. My work schedule is odd anyway.
I had the time at that moment to piddle while i waited on a call from some of my guys on a job site to support them. I bonded the input of the coil down stream of the blower moter leg, it really didnt matter to me but since you brought it up, i thougth it was a good idea to "feed" the coil upstream of the blower instead.

The point you made about the OEM fused lead to the heater function selector switch was valid, i flipped open the fuse panel layout and decided its needs a 15A fuse back in because this fuse is source for many many other sub systems. ~valid point you caught again.

The reason i added a symbol for a fuse on the top main input of the resistor bank is this.....
While in low, we have the thermal limiter in play for protection.
WHile in M1 & M2, i noticed at the last minute that there was no protection down stream of the inductive motor load and felt "why not", lets put a fuse there. In effect anything downstream of the blower would have protection. I am not satisfied with the over current protection sizes on any of these relay mods we have been working on thus far and for no other reason than a whim, i am just generically tossing in a 30A with the intent that a "low voltage" event "could" be real when a failure is in process. Normal current draws would certianly go up says ELI the ICE man.

are we good ? and to both of you does this option work to your satisfaction? it hopefully replicates the explorer layout and again, i am glad we took our time to get this done.

Protecting your blower motor switch (non-EATC)

Reply #41 – August 17, 2012, 12:12:44 AM

crazy 88,
your second bullet you posted above on post 34 finally sunk in, again valid point so i will say the thank you.
Bonding the input to the relay coil of K2 where i have it now is where i intended originally and now i see that the way it is drawn now for a ref wiring diagram is correct.

so,, you happen to be right about a lot but in the end good team work.

Protecting your blower motor switch (non-EATC)

Reply #42 – August 17, 2012, 12:32:26 AM

Yeah Scott everything is fine, no worries.

If I recall correctly, your last revision and Quietlef's are virtually identical, schematically speaking. As for the inclusion of F3 for some protection against inductive motor load, I assume that you are referring to the current surge by a collapsing inductive field. A fuse is not a valid method of protection in such a case, as the amount of current surge induced in typical DC motor would be far less than required to open F3, and would be completed by the time the fuse could react, assuming that the current would be high enough to trigger protection in the first place. Milliseconds of higher than normal current, while certainly undesirable, are not something, in this case to be worried about. We are attempting to protect a switch from excessive long term heat rather than a few milliseconds of high current with no voltage potential and some fairly high wattage resistors... oh yeah and ground.

If you have a spare few moments, can you elaborate on the other circuits that F1 is providing protections for? What is their total current draw? For that matter, is F2 a new fuse? If so, what is the current draw of the motor in high? Add about 500mA for the two relays (assuming Bosch 30A) and then we can size that F1 and F2 to actually protect the circuits.

Protecting your blower motor switch (non-EATC)

Reply #43 – August 17, 2012, 01:19:51 AM

just download the respective EVTM pages in my link below. that should get you started.

Im not gonna taket the time to clamp the ampacity draw on F1 at this time, frankly F1 could be sized a little or a lot lower depending on what you prefer as in what conditions or faults you want to factor in the engineered design.

Actually f2 should be something along the lines of approx 10A auto circuit breaker over current protection device but i just stuck a fuse there for no other purpose than to illustrate protection. If you dont think it needs ot be there then its a user choice i would think.

"F3" we could assume is the thermal limiter and this is typically faulty in many peoples cars now because its open, they get High only.

i have not clamped on the motor load in high either.

They are not identical for the reason you pointed out. In his, i see the switch is still in play and carrying current because it is upstream of the resistor bank.
This does not match up to the Explorer layout so in effect, the latest revision i show places the switch in question on the ground end of the whole circuit so there is no current draw at all "if" the contacts are not pitted or causing a small load.

trust me ,, i actually considered three breakers for the speed control "if" leaving the existing wiring as is and using those circuits to power a relay.

If you look back, it was implied that the intent was to totally bypass the speed switch complely during "high" only.

Protecting your blower motor switch (non-EATC)

Reply #44 – August 17, 2012, 01:51:22 AM

Quote from: jcassity;396161

just download the respective EVTM pages in my link below. that should get you started.

They are not identical for the reason you pointed out. In his, i see the switch is still in play and carrying current because it is upstream of the resistor bank.
This does not match up to the Explorer layout so in effect, the latest revision i show places the switch in question on the ground end of the whole circuit so there is no current draw at all "if" the contacts are not pitted or causing a small load.

This is the last diagram revision posted by quietleaf this afternoon in post #31. He, like you edited his existing diagram, updating the post body with notes and replacing the diagram of course to reflect the changes. I hope that you will review this diagram and come to see that my buttstuffysis that the two diagrams are virtually identical schematically is also correct. There may be a few minor differences, but for the most part, they are more alike than different.

Quote from: jcassity;396161

Actually f2 should be something along the lines of approx 10A auto circuit breaker over current protection device but i just stuck a fuse there for no other purpose than to illustrate protection. If you dont think it needs ot be there then its a user choice i would think.

Ok, I am confused again. Please tell me where in my last post I said that F2 was unnecessary? F2 is necessary, as this circuit is currently diagramed to provide protection to the secondary circuit, unless you were to tap F1 as the source voltage instead.

With regard to the circuit breaker, I wouldn't use a circuit breaker for this reason; the blower is a non-essential piece of hardware. The car will run fine without it and weather conditions not withstanding, can operate safely without the blower motor being operational. A semi critical system where I have see circuit breakers used might include semi-critical systems such as anti-lock brakes, head lamp circuits, hazard circuits, etc. In these limited cases, the limited functionality of a damaged circuit is preferred to operating without the semi-critical circuit.