Bogging, Stumble, Dying realted to blower function-STILL

During the summer I posted the following:

******************************************************************************************* 2000 with 90,000 miles just started the symptoms in subject line, three episodes so far in last 5 days. SEEMs like fuel starvation and will replace fuel filter first then test fuel pump BUT puzzled as to why symptoms only appear with AC on and blower on high. Could be just coincidence but thought someone would have a suggestion. Coolant temperature does NOT seem abnormally high according to gauge. Engine returns to normal after a shutdown and 30 minute *************************************************************************************************8 The problem never went away, we just avoided it by not using the blower on high Now that it has gotten cold it is still happening when using the heater. Now even with the blower on low, the problem poor running symptoms will appear after 30 or 40 minutes..

I think we have a bad blower motor. It is getting hot when run on high, or for long periods even an low, as it gets hotter, its resistance increases and draws more and more current to run until the current draw disrupts the FI system.

I am going to replace the blower motor. I see in the manual that the blower unit includes a resistor, I assume this is foe the low speed function and that for high the resistor is bypassed. This I am tentatively ruling out a bad resistor.

If anyone has any info to shed or disagrees with my diagnosis please post before I order a blower motor.

Thanks, Bob

Reply to
Bob Chappuis
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The blower motor may be bad. However, it also sounds like the alternator cannot keep up with the load. I would load test the battery(disconnected from the car), and see if it has excessive voltage drop under load. Next, I'd also load test the alternator. At 90,000, it may need brushes or have other problems. The fuel pump might be failing as well.

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Reply to
Chuck

I don't know about this, but it seems strange that increased temperature would *increase* current draw? Is there a controller involved?

I would have suspected engine temperature, (the temperature gauge is a joke, intended to keep consumers out of the dealer), but since it keeps happening in cold environments, I guess I am wrong.

Leon

Reply to
Leon van Dommelen

As the internal temp of the blower increases, the wire resistance would normally increase. BUT-- if the heat and expansion causes turns in the windings to short, any motor will draw more current. Another cause for increased current draw can be bearings. They may heat up and start to seize. Usually they make noise before this occurs. Usually, the fuel pump is cooled by the surrounding fuel, and this usually prevents most of the heat related problems encountered by motors such as the blower. The bearings in a fuel pump can have a high failure rate, since fuel is not a very good lubricant. It is also possible that the pressure relief valve in the tank is stuck open, and may cause low fuel pressure under high throttle settings.

At 90,000, a battery, fuel pump, fuel pump relay, and a blower motor replacement are all possibly needed. Load test the Battery and the alternator. If you can find (borrow) a clip on ampmeter, it can be used to test the blower motor for excessive current draw. This assumes you can get at the leads, which can be a problem in a small car such as the Miata. The fuel pump may be "dragging", and lower available voltage can cause it to slow down or even stop. After market fuel pumps are a common replacement solution. If you use one be sure to also get the install "kit" and a pigtail. It's likely that the connector from the old fuel pump to the in tank socket will need to be reused on an aftermarket pump. The install kit contains a new filter sock and some other useful parts. Total cost ifor the aftermarket is usually around $100, instead of the $230 or so for the pump from a dealer.

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Reply to
Chuck

The battery is the prime suspect. If voltage is marginal, ECU control over the fuel system can get flaky.

Reply to
Lanny Chambers

Thanks for the suggestions. I had the battery load tested yesterday and it is good. I bought a cigeratte lighter voltmeter while I was at the parts store. 13.8 volts at rest,

14.4-15.0 with the engine running. So the battery and altenator seem to be fine. Running the blower motor did not seem to have any significant effect on voltage, maybe .1 or .2 drop at most; but the bogging/stalling symptoms were not occuring either. On 15 mile drive home from the parts store I ran the blower on high the whole way, trying to reproduce the symptoms so I could observe the voltage but the engine performed flawlessly. ??????????????? Bob
Reply to
Bob Chappuis

"Put your hands on the radio, and feel the healing warmth!"

Reply to
Lanny Chambers

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