73 Fury Electrical Issues

[theos911]

It's been a long time since I've tinkered with the electrical irritations with my Fury, but quarantine has made for a good opportunity to revisit them. I'm trying to track down some things, none of which are showstoppers, but all of which are very irritating.

I suspect that some of these share a common cause while others have their own cause:
The headlights and dashlights dim noticeably at idle. The wipers also slow down somewhat. Add in the blower and the wipers crawl.
The blower on medium or high goes through fuses pretty quickly. I keep it on low or off to avoid this. My understanding is that the blower is the only thing on this fuse.
The fuel gauge always read low. At a full tank it reads 3/4, and throughout it's swing it shows less gas than is actually in the tank. I think this is a weak ground on the sending unit side of things.
The ammeter is and always has been nearly useless. It moves very little, and I don't recall it crossing from c to d at any point under any conditions.
The temperature gauge - and I'm pretty rusty on this since it has been years since I've had it connected - maxes out to hot as soon as the sending unit is connected and stays there if I recall correctly. I replaced the sending unit at one point, but the behavior persisted.

That's what I can recall for now, but unfortunately I haven't daily driven the car for quite some time. I'm looking to track down the cause of these issues rather than just manage the symptoms. I'm sure none of these were tolerable when new so something has got to be wrong. I'm not opposed to putting the headlights on a relay or bypassing the (already useless) ammeter, but that doesn't get me any closer to why all these don't work like they should.

Please let me know what you think might be going on.

Here are some voltages taken at high idle in park with various accessories on. (Obviously these are not representative of low idle in drive, but it's what I could grab this morning.)
Battery (key off) 12.4v
Idle 14.8v
Headlights on 15v
Wipers on high 15v
Both headlights and wipers on high 15.2
Blower low 15
Blower medium 15.1
Blower high 15.2
Blower high and headlights on 15.4
All three 15.5

 

[Big_John]

The headlights and dashlights dim noticeably at idle. The wipers also slow down somewhat. Add in the blower and the wipers crawl.

This could be a bunch of things. Since the voltages improve at higher idle, I think the voltage regulator is functioning. It may be a bad diode in the alternator or could be as simple as the idle speed is too low. I would start by checking all the battery cable connections and grounds. Some of this is nature of the beast... But since you mention the blower and it blowing fuses, I'd like to know if you have the same low voltage with the blower off. See the next comment.

A prudent thing to do is remove the alternator and have it tested (free) at one of the Auto Zone/Advance Auto type chain stores.

The blower on medium or high goes through fuses pretty quickly. I keep it on low or off to avoid this. My understanding is that the blower is the only thing on this fuse.

If you are blowing a fuse, that means that you have an excessive current draw through the circuit. That points to a bad blower motor. Not uncommon... They get old and they start to draw more current as they don't turn over. I'd look over the wiring and connections too.

The fuel gauge always read low. At a full tank it reads 3/4, and throughout it's swing it shows less gas than is actually in the tank. I think this is a weak ground on the sending unit side of things.

Very likely it's a bad ground to the tank sender, but a bad sender or voltage limiter can also cause this. I've given up on using the clip that everyone seems to think is the answer and running a dedicated ground wire to the sender.

The ammeter is and always has been nearly useless. It moves very little, and I don't recall it crossing from c to d at any point under any conditions.

The ammeter in your '73 (IIRC) is a shunted ammeter where most of the current doesn't flow through it, so the advice you'll see about bypassing it doesn't apply. What is important is the main power wire at the bulkhead connector and if you look under the steering column, you'll see a multiple wire connector with (I'll bet) a burnt mark where the red wire goes through. Rerouting that wire around the connector is easy and a good fix.

The temperature gauge - and I'm pretty rusty on this since it has been years since I've had it connected - maxes out to hot as soon as the sending unit is connected and stays there if I recall correctly. I replaced the sending unit at one point, but the behavior persisted.

I'll bet on a bad gauge. But check the wiring. If the wiring is shorted to ground at some point, that will make the needle move to full "hot".

 

[commando1]

^^ ^^
Excellent summary of starting with the basics first and then taking it from there.

 

[cbarge]

I'll bet on a bad gauge. But check the wiring. If the wiring is shorted to ground at some point, that will make the needle move to full "hot".

The gauge voltage limiter can be suspect as well.

 

[3175375]

It's been a long time since I've tinkered with the electrical irritations with my Fury, but quarantine has made for a good opportunity to revisit them. I'm trying to track down some things, none of which are showstoppers, but all of which are very irritating.

I suspect that some of these share a common cause while others have their own cause:
The headlights and dashlights dim noticeably at idle. The wipers also slow down somewhat. Add in the blower and the wipers crawl.
The blower on medium or high goes through fuses pretty quickly. I keep it on low or off to avoid this. My understanding is that the blower is the only thing on this fuse.
The fuel gauge always read low. At a full tank it reads 3/4, and throughout it's swing it shows less gas than is actually in the tank. I think this is a weak ground on the sending unit side of things.
The ammeter is and always has been nearly useless. It moves very little, and I don't recall it crossing from c to d at any point under any conditions.
The temperature gauge - and I'm pretty rusty on this since it has been years since I've had it connected - maxes out to hot as soon as the sending unit is connected and stays there if I recall correctly. I replaced the sending unit at one point, but the behavior persisted.

That's what I can recall for now, but unfortunately I haven't daily driven the car for quite some time. I'm looking to track down the cause of these issues rather than just manage the symptoms. I'm sure none of these were tolerable when new so something has got to be wrong. I'm not opposed to putting the headlights on a relay or bypassing the (already useless) ammeter, but that doesn't get me any closer to why all these don't work like they should.

Please let me know what you think might be going on.

Here are some voltages taken at high idle in park with various accessories on. (Obviously these are not representative of low idle in drive, but it's what I could grab this morning.)
Battery (key off) 12.4v
Idle 14.8v
Headlights on 15v
Wipers on high 15v
Both headlights and wipers on high 15.2
Blower low 15
Blower medium 15.1
Blower high 15.2
Blower high and headlights on 15.4
All three 15.5

Others have provided good leads. A couple of things to consider are:

1) you could remove power and ohm out the circuits in question. PIA, but it will reveal the truth.

2) regarding the blower motor, there may be something that got sucked into the squirrel cage. My Uncle’s Country Squire had no moving air, but the compressor was engaging and working. Turns out that a pair of my Aunt’s nylons got sucked into the squirrel cage and grossly limited the blower and blew fuses...

 

[NewportRbod]

Others have provided good leads. A couple of things to consider are:

1) you could remove power and ohm out the circuits in question. PIA, but it will reveal the truth.

2) regarding the blower motor, there may be something that got sucked into the squirrel cage. My Uncle’s Country Squire had no moving air, but the compressor was engaging and working. Turns out that a pair of my Aunt’s nylons got sucked into the squirrel cage and grossly limited the blower and blew fuses...

I'd like to hear the story of the nylons! They were always a pain to remove. Sorry, my minds always in the gutter.

 

[3175375]

I'd like to hear the story of the nylons! They were always a pain to remove. Sorry, my minds always in the gutter.

Here is what I know:

My Mom’s older sister, her husband and their 4 kids were driving to my parent’s house in SoKal. Somewhere around St. George, Utah, the heat was becoming unbearable and the blower didn’t spin. I believe that a fuse protecting the wiring had blown and my Uncle replaced it and had isolated the fuse blowing to the blower.
They rolled down the windows and got to my parent’s house. I believe that they were in a late 60’s ranch wagon.
My Dad helped my uncle tear apart the heater / evaporator box and found a pair of nylons wrapped around the squirrel cage fan. I suspect that my aunt had taken off the nylons and placed them in the passenger footwell. I suspect that the blower sucked the nylons into the box...