blower problems; circuit breaker question

Hi I'm new to these forums. I have a 1997 Ford Escort and the blower just randomly stopped working the other day. I have searched through the forums here and found that faulty wiring, the resistor, or the blower motor itself could be the culprit. I actually can't take a look at the car again until tomorrow afternoon to see which of these it is, but I want to make sure I can rule out the 30A circuit breaker that's near the fuse panel. I would assume that if the breaker tripped, the reset button would pop out? With an ohmeter they are reading nil across the breakers. I swapped the heater 30A with the one for the upper-right hand fuse panel (they are identical) and that had no effect ... which led me to believe that it was something on the blower itself and that both breakers were fine (however the cigarette lighter does not work, and the 20 amp fuse for it is ok ... I just never use it so it's not of much concern to me). Just want to rule that out before I (possibly) shell out cash for the resistor or motor. Thanks!

Hello Fiverz, and welcome to the forum. Here is some Ford service info which refers to the 1995 north American Escort range, describing the mode of operation for each of the different type of circuit-breaker in use at that time.

I just woke up from a nap so my head's a little fuzzy but when that clears I'll read through your fault symptoms again and make some comments.

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Circuit Breaker

Some circuits are protected by circuit breakers (abbreviated "c. b." in fuse chart). They can be Fuse Panel mounted or in-line. Like fuses, they are rated in amperes.

Each circuit breaker conducts current through an arm made of two types of metal bonded together (bimetal arm). If the arm starts to carry too much current, it heats up. As one metal expands faster than the other the arm bends, opening the contacts. Current flow is broken. A circuit breaker can be the cycling or non-cycling type.

Fuse Panel Mounted Cycling Type:

http://img57.imageshack.us/img57/3508/cb001dq8.png

In - Line Mounted Cycling Type:

http://img266.imageshack.us/img266/1606/cb002hb2.png

In the cycling type, the bimetal arm cools and straightens out. This cycle repeats as long as the overcurrent exists and power is applied.

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Fuse Panel Mounted Non - Cycling Type

http://img75.imageshack.us/img75/9730/cb003ho5.png

Fuse Panel Mounted Manual Reset Type

http://img458.imageshack.us/img458/3352/cb004du3.png

Two types of non-cycling circuit breakers are used; one is reset by removing power from the circuit, and the other is reset by depressing a reset button.

In the first type, there is a coil wrapped around the bimetal arm. When an overcurrent exists and the contacts open, a small current passes through the coil. This current through the coil is not enough to operate a load, but it does heat up both the coil and the bimetal arm. This keeps the arm in the open position until power is removed.

In the second type, a spring pushes the bimetal arm down and holds the contacts together. When an overcurrent condition exists and the bimetal arm heats up, the bimetal arm bends enough to overcome the spring and the contacts snap open. The contacts stay open until the reset button is pushed and the contacts snap together again.

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I'll just briefly describe the operation of the heater blower circuit - I don't know how much you know about electrical circuits, so excuse me if I'm only stating the obvious here.

A basic circuit can operate in one of two ways:

1. The negative side of the component (e.g. lamp, motor, etc.) can be permanently connected to ground, with the positive feed being switched in and out of circuit as required, or:

2. The positive feed can be permanently connected, with the path to ground being switched in and out as required.

Your blower circuit is of the latter type. If you refer to the wiring diagram on this thread (http://www.automotiveforums.com/vbulletin/showthread.php?t=668455), you can see that the positive pole of the motor is fed via the 30A circuit breaker at the top of the diagram. This breaker is labelled 'Hot in RUN', meaning that it is permanently fed with 12V whilst the ignition key is in the RUN position.

All that remains in order to make the motor function is to complete the path to ground from the negative pole of the motor, and that is the purpose of the rest of the circuit. In order to run at full speed, it connects, via the blower switch, directly to ground. In order to run at MID HI, it connects to ground via the first 0.5 ohm resistor and the blower switch. In order to run at MID LO, it connects to ground via both the first and second 0.5 ohm resistors in series (total 1.0 ohms) and the blower switch. Finally, in order to run at LO, it connects to ground via both of the two 0.5 ohm and the single 1.3 ohm resistors, all in series (total 2.3 ohms) and the blower switch.

Now then, you have already verified that you have continuity through the circuit breaker (measured at zero ohms and also verified by substitution with another device), so we know that the breaker is healthy. What we don't know is whether 12V is actually being fed into that breaker or not, so that would be my first check, if access is possible - check for 12V at the breaker. If it's the plug-in type, where the pins aren't accessible after it's plugged in, then unplug it and probe into the socket - one side only should now read 12V. You will of course need the ignition switch to be in the RUN position at that time. If access is possible, it would also be a good idea to check that the 12V is arriving at the motor positive pole, because that section of wiring could be open-circuit.

As far as the resistor bank is concerned, any or all of those resistors could go open-circuit but still not prevent the blower from running at full-speed via the straight-through connection. So I don't think the problem is with the resistors, but the straight-through connection within that resistor bank could be open-circuit, or there could be an open-circuit at the input or output connectors so you can't rule the resistor bank out completely.

Following the resistor bank, we have the blower speed selector switch, and an open-circuit in the switch contact common rail, or the input connector, or the output connector, could all produce your fault.

Finally, the ground lead which runs from the selector switch common rail to ground could itself be open-circuit.

If you're able to verify that 12V is reaching the motor, then my next step would be to take a length of wire and bypass the rest of the circuit - just connect the motor negative pole directly to ground - the motor should then run at full speed (so long as the ignition is in RUN) and that would confirm that the motor is healthy and you therefore have an open-circuit fault somewhere in the ground return path from that point onwards.

If, on the other hand, the motor failed to run, then that would require further investigation of the motor itself, which may have developed an internal fault.

I'm fairly sure that you have an open-circuit somewhere, or a faulty motor. I don't think that you have a short-circuit condition, because apparently the click of the breaker is clearly audible, so I think you'd hear it if a short was causing it to trip.

I hope that will be of some assistance, and if you have any questions then feel free to ask.

Good luck.

Cool thanks for the info guys. Yea I just wanted to be sure that the circuit breaker button was supposed to pop when blown. I was going to proceed with the testing mentioned above during the afternoon tomorrow (Chicago burbs are damn cold right now ... gotta get in the warm, albeit dark, garage with a torch). Thanks again for the replies ... I'll post back tomorrow with my findings.

Some additional info on this one, possibly of relevance, gleaned from the other blower motor thread (http://www.automotiveforums.com/vbulletin/showthread.php?t=668455) which I mentioned earlier.

If your wiring is the same as the '95 model, then it's possible that the blower motor, powered windows and the wipers are all fed from the same circuit breaker. So, you might want to verify that the wipers and powered windows, if you have them, are still working. If not then obviously your fault is not confined to the heater circuit, and you would turn your attention to the 12V feed into, and out of, the breaker.

If it seems that it is just the blower motor which is faulty, then proceed with fault-finding on that circuit. Be aware, however, that what I was saying about not suspecting a short-circuit, because you can't hear a click from the breaker as it disconnects, is no longer valid. Apparently, the clicking sound referred to in the other thread cannot be coming from the breaker because that has been bypassed and is no longer in circuit. Also, apparently, that wiring diagram may not be accurate and may not be complete. Therefore a short-circuit is back on the list of possibilities, so be aware of that if you find that the 12V feed is not reaching the blower motor - there may be a fuse, or a circuit breaker, in the 12V feed to the motor which we're not aware of, and which may have tripped.

It was something really simple. In my particular model there is a blue/black wire going from the blower motor to a central "bank" if you will that had another multi-colored cable going to it ... that goes through the firewall into the engine compartment. On the firewall there is a male plug sticking out (like one of the prongs on a normal hair dryer or whatever you plug into an outlet). On the blue/black wire there is a plastic clip and the wires are soldered on to a clip that kinda looks like

nn

there the tops of the "n's" force the flat part down onto the male clip when it's connected. Both metal parts were slightly corroded and blackened and a small amount of plastic was melted. All I did was take a 30 cent emory board and cut it so that it would fit and reach all parts, and scraped all the black material off. Once the metal parts were pretty much shiny new, I reconnected it and viola I had my blower again. I am sure that that wiring will need replacing soon, and I am assuming that I can get that at my Ford dealer but it's just too damn cold out here now (-4, 18 in my garage) to be messing with it any further.

Now one other question I have ... is there another problem that would have caused the plastic to melt a bit, or is that just from use? I've read on here and other forums that it seems to be faulty for 90s escorts every so often. Thanks again for all your help!

It was something really simple. In my particular model there is a blue/black wire going from the blower motor to a central "bank" if you will that had another multi-colored cable going to it ... that goes through the firewall into the engine compartment. On the firewall there is a male plug sticking out (like one of the prongs on a normal hair dryer or whatever you plug into an outlet). On the blue/black wire there is a plastic clip and the wires are soldered on to a clip that kinda looks like

nn

there the tops of the "n's" force the flat part down onto the male clip when it's connected. Both metal parts were slightly corroded and blackened and a small amount of plastic was melted. All I did was take a 30 cent emory board and cut it so that it would fit and reach all parts, and scraped all the black material off. Once the metal parts were pretty much shiny new, I reconnected it and viola I had my blower again. I am sure that that wiring will need replacing soon, and I am assuming that I can get that at my Ford dealer but it's just too damn cold out here now (-4, 18 in my garage) to be messing with it any further.

Now one other question I have ... is there another problem that would have caused the plastic to melt a bit, or is that just from use? I've read on here and other forums that it seems to be faulty for 90s escorts every so often. Thanks again for all your help!

That's excellent news - I'm pleased that you got it fixed, and thanks for letting us know. That type of connector is commonly referred to as a 'spade' connector here in the UK - I've no idea what the proper name for it might be, since that's all I've ever known it as. I'm sure that will run quite happily for a long time, but sooner or later the connector is likely to corrode and cause the same fault again. You can provide a permanent fix for that by coating both parts of the connector with a protective coating prior to reassembly, and the connector would then be good to last for the lifetime of the vehicle - the coating locks out oxygen and atmospheric moisture, and that inhibits the corrosion process. Here in the UK I use something called petroleum jelly for that purpose - the trade name is Vaseline and I buy that at any pharmacy. If that doesn't sound familiar then use whatever you would normally use to protect car battery terminals. There's no hurry over that so leave it until the warmer weather if you want, but if you do let any length of time elapse between now and doing that, then give the connector a good clean again before applying the protective coating.

As for the melted plastic housing - that was caused by heat being dissipated at the connector, and that happened because corrosion had occured, and that had caused the resistance of the connector to rise - that then caused a voltage to be developed across the connector, and that in turn had two effects - firstly, it reduced the voltage available to the blower motor and prevented it from working, and secondly it produced the heating effect in the connector itself.

By cleaning the connector, you have now reduced the resistance of the connector back to zero (ohms) and therefore no voltage can be dropped at that point and therefore no heat can be produced at that point either. So put a protective coating on that connector when you have some free time and then you can forget about it and it won't ever trouble you again.