Auto Pilot & A/C blowing my fuse... help

[Ambush]

Hey gang - I have a 1965 Imperial and I've run into one of those little electrical issues that just come out of now where. The fun kind. So the back story first.
I have auto pilot equipped and it does sort of work, never had it to cause a fuse to blow. Now recently I had my A/C worked on - it's an old school RV2 compressor and all original to the car. It was supposedly rebuilt according to the prior owner but who knows. I took it to my garage to get everything working for the summer heat. They got it running and for a short time it was working. SO I turned my attention back to servicing the AP ( auto pilot ). It was not quite holding speed like it should, but the "speed minder" function was working well. Well one day the A/C stopped working and found out that the compressor was broke and would need to be rebuilt, maybe for the first time. SO I paused my work on the AP and went back to the A/C. After a few weeks, the compressor came back and I had everything re installed and ...working again ...so far it's beed fine.

This bring us up to current time. Now since I've got the A/C working now for the 2nd time, an new issue has arose. I have discovered that the AP is blowing a fuse. The first time the A/C was worked on and working for a short time, I was able to also operate the AP with anything blowing. Now I can't even run the power to the AP w/out it blowing the fuse as soon as I turn the key. And BTW when it blows the fuse, it also disables the A/C from running. Apparently the AP and the A/C share the same fuse; which is a 20amp, and is marked on the fuse block as the ACC --- RR. A/C fuse. What does the RR. stand for? Is the A/C on the correct fuse here? Accourding to the wirirng diagram the AP should be there, but I'm not sure about the A/C or RR. A/C whatever that means. And why is it blowing fuses now, when before both accessorins were operating fine w/out blowing a fuse? No one has messed w/ any wiring, so I'm at a loss ...please chime in with any ideas on this.

 

[Big_John]

What does the RR. stand for?

I believe it means rear defogger.

 

[Ambush]

Ok I can buy that ...I though it may stand for something "rear". Do you know if the A/C is supposed to be there, on that fuse with the AP? If I'm reading my wiring diagram right, it should be on the Heat --- A/C fuse, another 20amp ...but I'm not sure.

 

[Big_John]

Ok I can buy that ...I though it may stand for something "rear". Do you know if the A/C is supposed to be there, on that fuse with the AP? If I'm reading my wiring diagram right, it should be on the Heat --- A/C fuse, another 20amp ...but I'm not sure.

I looked at my '65 FSM and you are correct.

If you look at the back of the fuse block, I'll bet that feed wire is plugged into the wrong circuit.

 

[Ambush]

I looked at my '65 FSM and you are correct.

If you look at the back of the fuse block, I'll bet that feed wire is plugged into the wrong circuit.

That's worth a look see ... are the wires soldered in on the block, I forget?

 

[Big_John]

That's worth a look see ... are the wires soldered in on the block, I forget?

Should look something like this. Some have a connector and some don't. I've never done much with an Imperial, but the Chryslers looks like this. I expect the Imperial will be similar.

 

[Ambush]

This is what I have behind the block. Everything seems to be going into the right place. But I'm still unsure of the light green wire. According to the diagram that's the color for the rear defogger. My car does not have that feature, but instead has the AP which is the red wire, on the same circuit as the light green ...stacked on top. Now I'm assuming that the light green must also be the color for the A/C, ( even though I can't find that traced in the diagram ) because when that fuse blew ..the A/C did not work. The color of the wire in the engine bay that comes from the compressor clutch is a blue-grey color and remains so to the firewall ...so it must change to light green once through the firewall to the inside of the car.

SO IF this is all correct that would mean that somehow the rebuilt compressor is pulling too much voltage, and when combined w/ the AP, is blowing the fuse. Does anyone know what the A/C should pull ( RV2 style compressor) and what the AP should pull? Remember they're both together on a 20 amp fuse so it has to be within that tolerance. What's the best way to check to see what my A/C is pulling? Would it be a bad idea to try a 25 amp fuse in there? Thoughts?

 

[Big_John]

Would it be a bad idea to try a 25 amp fuse in there?

Yes, it would be a bad idea.

It doesn't make a lot of sense to me to have that green wire there. You could try disconnecting the green wire and put in a new fuse and see what happens.

 

[Ambush]

I'm gonna do that tomorrow ...but I suspect pulling out the green will kill the power to the compressor clutch. We'll see.

 

[cbarge]

The AC will pull a lot of current.
Especially with a freshly rebuilt compressor thats tighter than a well used one.
I recommemd integrating a relay within the AC circuit.
It will take away the load on the fuse panel should there be other accessories sharing that fuse.
Also as a process of elimination...body is ground.
A freshly painted compressor may not have a good ground. Clean up the mounting contacts between the compressor and engine for a good ground.
Hope this helps

 

[Ross Wooldridge]

The green wire in your photo looks to be added in after the fact, as the remaining wires come in and out through the side openings in the fuse box as they're supposed to.

The red wire that shares the same post as the green wire noted above is a main power feed wire going to something that draws significant power, hence it's thicker than most. I suspect that particular circuit is overloaded, possibly by the green wire.

Rummaging around in my wiring diagrams -

Heat/AC dash control is fed 12V and is usually black with tracer. It feeds 12V to the blower motor resistor, and the blower motor resistor is controlled by the fan switch on the dash, and it's feed wire is usually dark or light green.

Autopilot feed wire is typically RED... and its other wires are light blue and black, with an orange wire for the dial light. It runs off the accessory circuit along with the rear defogger. Rear defogger feed wire to the rear defogger switch is light green...

Compressor clutch feed wire at the compressor is usually dark green.

Rear defog and the autopilot are run off the accessory circuit, which when looking at the back of the fuse box, is the fourth from the left terminal. It looks like those two items are in their proper terminals in your photo IF they are actually the AP and the rear defog. Best to start tracing those wires from there...

Don't know if I've been helpful or not.

 

[Ambush]

All good responses, tells me a lot.
I did just for kicks and giggles disconnect the light green wire on the back of the fuse block. Sure enough the A/C compressor wouldn't work ... Plugged it back, A/C kicks on. SO the light green wire is powering the A/C compress on the fuse block. It may also be that the light green color is correct for the A/C compressor. I saw the back of another fuse block from a 1965 Imperial equipped with A/C and rear defogger, but without AP. They showed 2 light green wires, one was for the rear defogger, as the wiring diagram specifies.. and the other was for the A/C. They were double stacked on the same side of the fuse. That's just how mine is except I have the AP red wire stacked on top the A/C light green. And yes, I Looking at the same fuse slot/circuit ( ACC --- RR. A/C ), where my Auto Pilot and A/C are connected.

 

[UGW]

The AC will pull a lot of current.
Especially with a freshly rebuilt compressor thats tighter than a well used one.
I recommemd integrating a relay within the AC circuit.
It will take away the load on the fuse panel should there be other accessories sharing that fuse.
Also as a process of elimination...body is ground.
A freshly painted compressor may not have a good ground. Clean up the mounting contacts between the compressor and engine for a good ground.
Hope this helps

Some good ideas here. My first thought was that since this didn't happen until the AC was rebuilt, the new component was pulling more amps than the old. Something could be too tight, or maybe it isn't an exact replacement? It's possible later units could look the same but pull higher current?

The relay is an interesting idea - you can get relays with a built-in ATC fuse slot for not much money. This is how most cars have worked for at least the last 20 years, so it's not an oddball solution.

HOWEVER remember that on a 65, your whole charging system runs through the ammeter in the dash, and the factory alternator didn't make more than 50A. If that fuse is blowing, it's doing its job! Don't try to band-aid fix this; find the real cause. If you try to work around it without finding the culprit, you could set your dash on fire.

 

[Ross Wooldridge]

I'm actually not sure how a rebuilt compressor can pull more electrical draw under load than not. The compressor is strictly mechanical. The clutch is the only electrical device, and - please correct me if i'm wrong here - it's my understanding that the AC clutch is simply an on/off device - and it functions magnetically, using material that will wear (like any friction-based grip device).

If the compressor itself (which is a strictly mechanical device), is too tight because it's rebuilt, the clutch will either slip and smoke, or let go entirely. The clutch's twelve volt draw won't change. It's either on or off.

What will change with compressor condition/under load etc., is the horsepower draw on the engine. Too tight sucks more horsepower.

So this leads me to believe that the reason the fuse is blowing is not necessarily centered around how much current draw the AC clutch uses... it's my belief that there's another issue somewhere.

 

[UGW]

I'm actually not sure how a rebuilt compressor can pull more electrical draw under load than not. The compressor is strictly mechanical. The clutch is the only electrical device, and - please correct me if i'm wrong here - it's my understanding that the AC clutch is simply an on/off device - and it functions magnetically, using material that will wear (like any friction-based grip device).

If the compressor itself (which is a strictly mechanical device), is too tight because it's rebuilt, the clutch will either slip and smoke, or let go entirely. The clutch's twelve volt draw won't change. It's either on or off.

What will change with compressor condition/under load etc., is the horsepower draw on the engine. Too tight sucks more horsepower.

So this leads me to believe that the reason the fuse is blowing is not necessarily centered around how much current draw the AC clutch uses... it's my belief that there's another issue somewhere.

Hmmm, that does seem to make sense. I didn't think about the compressor being mechanical. I did notice the fuse block on my '63 does say "ACC. 15A - RR-AC 20A" on the same slot, which I've always interpreted as meaning that cars with AC needed more current, hence a bigger fuse. So, it needs more current for something related to the AC?

However, (this is just armchair electrical engineering, I barely passed that class in college and that was 20 years ago) it is my understanding that a 12V draw is different than amperage. You car's voltage should always be around 12.5 - 14V, but the amps will change based on load. Somebody tell me if I am wrong, but doesn't a starter draw hundreds of amps but only 12 volts? Also, your stereo turned all the way down or up is always 12V, but amps increase with volume. Amps are what blows the fuse.

So, if the clutch needs more AMPS to engage than before, that could blow the fuse. I don't know what would cause that condition? Bigger magnet? It could also be something else, like a blower motor.

One final fact: fuses (and breakers) work on heat. If too much amperage goes through the wire in the fuse, it melts and interrupts the flow of electricity. The idea is that the fuse melts before your wiring catches on fire. This is important because the speed at which the fuse blows is related to how much over the specified amperage flows through it. For example, if you have a 20A fuse, you could run 21A through it for a very long time before it blows. It might not ever blow, depending on tolerances. On the other hand, if you put 200A through that same fuse, it will blow relatively quickly. So, it stands to reason that if a fuse is taking a few minutes to blow, you're looking at amperage that is a little bit higher than normal, but not a ton. It's also possible something is causing short, high spikes in amperage which would trigger the fuse.

Understanding the basics of electricity by thinking of it as water

 

[Ross Wooldridge]

Hmmm, that does seem to make sense. I didn't think about the compressor being mechanical. I did notice the fuse block on my '63 does say "ACC. 15A - RR-AC 20A" on the same slot, which I've always interpreted as meaning that cars with AC needed more current, hence a bigger fuse. So, it needs more current for something related to the AC?

However, (this is just armchair electrical engineering, I barely passed that class in college and that was 20 years ago) it is my understanding that a 12V draw is different than amperage. You car's voltage should always be around 12.5 - 14V, but the amps will change based on load. Somebody tell me if I am wrong, but doesn't a starter draw hundreds of amps but only 12 volts? Also, your stereo turned all the way down or up is always 12V, but amps increase with volume. Amps are what blows the fuse.

So, if the clutch needs more AMPS to engage than before, that could blow the fuse. I don't know what would cause that condition? Bigger magnet? It could also be something else, like a blower motor.

Yes, you are correct! I apologize for using layman's terms - thanks for the guidance! Yes, amps is what I meant when I said draw. At any given operating voltage, in this case nominally 12V, the amperes drawn by the AC clutch should be the same regardless of the compressor's load, and the clutch will either do its job or fail trying. Yes - I should have said amperes.

Regarding your comments about the fuse box load rating - if the car has rear Defog, AC, Rear AC, (like my wagon), and it is powered off the Accessory circuit, then it's expected that the ampere fuse rating would need to be increased a bit because there are extra blower fans - in addition to the dash blower fan there would be a blower fan in the rear defog, or a rearAC box typically on the same Accessory circuit as well as the AC compressor clutch, hence the additional info in the rating by the fuse's slot.

 

[Ambush]

Gentlemen this has definitely sparked some lively debate. I appreciate all the ideas and responses of problem solving that has gone on. I have been working on the problem too, and had solved it, or at least figured out why.

I took the A/C off the circuit and began working on the AP ( auto pilot). It needed some service anyway, and I've been trying to bring it back to fully functioning status. It was working, but not all the way. In the process of opening it up, cleaning, adjusting, closing back up, testing ...repeat ...repeat ...repeat. I found that during this process the same fuse would still blow out. Keep in mind this is with the A/C off the circuit.
Long story short, it was human error likely the whole dang time. Sometimes during the AP test and adjustments ...I was failing to take the power off of it ( or disconnect battery ), and apparently removing and replacing the cover on it would spark a short-out in someway and "boom" the fuse would blow. Now I did mess with the AP when the rebuilt A/C compressor was reinstall on the car ...so it was me doing that, ( not the A/C ), which caused the fuse to blow. I'll gladly take a little red face over this, so long as everything now can play together without poppin' a fuse ...we're good and and everyone's happy.

Thanks again guys, a tad embarrassed, but wiser.

 

[Ross Wooldridge]

Hey - glad to hear that you've found the issue. Yup, always disconnect the battery! Been there, done that. Had one blow up on me years ago. Case smacked off my left ear...

Did you get the accel function working better on the AP yet?

 

[Ambush]

Hey guys, if you can lend me a little more help.... Now that I've solved the fuse issues I started using the A/C again. Now remember the compressor was just recently rebuilt and reinstalled by a garage that not necessarily classic Chrysler experts. -So up till now I've not had my A/C in use. The A/C does work, in that it will blow cold, but I'm having trouble with the A/C being very noisy low rumbling, lot's of vibration, and the belt's dancing like crazy (2 belts that go to the Alt and the compressor clutch ). I read this last night about this type of issue.

1964-1966 Imperial

Technical Tips

Chris Hawkins​

A/C compressor noise and vibration - You should not feel any vibration when your air conditioning compressor comes on, only a slight drop in RPM. If there is vibration and noise, do not immediately assume your compressor is at fault. Tighten all the mounting bolts associated with your compressor. If you find they were already tight, don’t give up. 9 times out of 10 the source of vibration will be your alternator brackets. Oddly enough, I have discovered that the lower mounting bolt on the alternator is most often the primary cause of any compressor vibration and dancing fan belts. Be sure this bolt is tightened securely and your vibration problem will quite likely disappear. Fanbelts - Be certain you are using the correct length belts - the shorter the belt the less chance for vibration. If your parts counter person cannot find a specific fan belt listing for your Imperial, do not assume the equivalent year Chrysler with the same sized engine used the same alternator-A/C belts. They did not. The Chrysler Parts Manual gives the same alternator-A/C fan belt part number for the equivalent year Dodge or Plymouth with a 361 or 383 engine w/ AC. For whatever reason, a longer length belt is used on all Chryslers!

SO if this gentleman is right, I should not have all this vibration, noise and dancing fan belts. First things first. The belts. I have 2 and maybe they are not correct? Can you guys tell me what are the proper 2 belts I need ( modern equivalent for my engine; which is a 413 - 1965 Imperial Crown Coupe ). If you can help me, be sure I have the right belts or point me to where I can get them, I can eliminate that as a problem. I like to get my parts like this at Napa ...but I'll get who ever sell the right belts.

I also read this article here: ( Chrysler Alternator Belt Tension Tool ) Question, do I need this part too to set the tension correctly or is there a work-a-around?
Thanks

 

[Ross Wooldridge]

The belts are long sadly, and back in the day you used to get a pair of matched belts. They were cut from the same stock piece of belting tube - one after the other.

That doesn't exist anymore.

Regardless, proper belt tension is key, and if the alternator bolt doesn't have the spacer that runs through the alternator and acts as a bushing, plus the other spacer behind the alternator, then you'll get rumble.

I find I have to use an old snow shovel handle to pull the alternator tight enough to get satisfactory tension on the belts.