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1988 Crown Victoria Heating + Alternator

Hi guys. I just have a general question.

Is there any possible way having the heater on with the fan at max can kill an alternator?

If it does kill the alternator, would it be that the alternator itself is bad? Or could it mean that there’s a separate problem with the car?

I’m asking this because there was one point where I had the original alternator, but then when I used the heater and had the fan set to max, I noticed that my blinkers would get slower depending on what setting I had the fan set to. But then, over time, even without using the fan, my blinkers would get slower and slower until the car wouldn’t start anymore. I figured the alternator was just very old and needed to be replaced, and so I replaced it and everything was back ship shape. I bought a brand new gold battery along with it. I replaced both these things about 3 weeks ago.

Then, figuring that now that I have a new alternator, I thought that I could have the fan at max along w the heating now and there’d be no problems, but to my luck, the problems struck, but this time with a warning. This past Saturday (Nov 2nd, 2019) The AMP light was on. As I continued driving it, both the turn signals started blinking slower and slower over time and starting the car would slowly start sound like the car was having trouble. That Saturday I tested this new alternator I had gotten 3 weeks ago by starting the car and disconnecting the battery and the car just shut off. That was the obvious hint that it was the alternator.

So Sunday, it got to the point where the car just died on me when I was on the way to the parts store to exchange the alternator for a new one. I needed a jump start from someone and I was on my way. They took a look at it and the voltage and things and it was obvious it was the alternator.

After replacing it again, I now have a newer one. and since Sunday, I was thinking that it’s gotta be the heater with the high fan setting that’s doing this, so I kept the fan on a low setting and everything was fine. when I had the fan on the lowest or 2nd to the lowest setting, I noticed that my blinkers blinked a tad bit slower, but it’s barely noticeable.

Just tonight, I accidentally set the fan to max or second to max with the heater on and now I’m noticing similar problems to what I had before. Immediately, the right turn signal blinker blinks slower than the left one, which blinks at the normal speed. and inside the dash, the right blinker doesn’t even blink anymore, yet outside the car, the front and back still blink.
So now I’m worried I might’ve killed this brand new alternator once again. I didn’t do that test where I disconnect the battery yet to see.

The auto parts store I went to was Advance Auto Parts. When I got to get the alternators, they already had both in stock, so I’m not entirely sure if they were used or not. They both looked brand new. the wires and everything. They were the right size and seemed to be the right amount of amps; they both looked identical to the original.

If anyone has any idea what’s going on, let me know. Is it just my luck that I had gotten 2 defective alternators? or is there something wrong with my car?

The amps of the standard alternator in that car should handle the fan at full speed with.the headlights on. Please do NOT disconnect the battery with the engine running unless you want to buy another PCM. It’s a sure way to fry it. I’d also find a better source for a new alternator, perhaps a Ford dealer.

After getting it replaced the last time, they told me I should never disconnect the battery while it’s still on, so I won’t do that again. Thanks for the info


After leaving the car off and parked in the driveway for about 30 minutes, I hopped back in and turned it on and everything was back to normal…
It seems the alternator is alright and it was a false alarm…

One question I have is that, even though the blinkers still work when the fan is on, the higher the setting, the slower they seem to blink.

Is that normal for an old car like that?

To clarify, they exceptionally blink slower when I’m stopped, but go back to a normal speed when I’m pressing the gas. This way always the case.

When the system voltage drops the blinkers will blink more slowly. Suggest to measure the battery voltage when the engine is running, comparing it when the fan is on max vs off. fyi You can get a pretty good idea about system voltage problems by looking at a reflection of the headlights when you are parked in front of a window for example. Compare it for example with the engine off, vs engine running. It should be noticeably brighter with engine running.