I thought the AC high fan voltage came straight from the wire harness/alternator. At least on my 78.
Drinking the Koolaide... š
- Thread starter Tybalt39
- Start date
One of these days, I'll have to dig into the manual that was provided to me for this coach. I've got two batteries up front, one off each end of the isolator. I've also got two batteries back by the Onan. They were big and beefy and probably 6 volt deep cycles wired in series. At this point, I'm not certain which are the house batteries. Normally, I would have assumed the batteries back by the generator were just to start the generator. But then why not a starter battery instead of two deep cycle 6 volts which were more commonly used as house batteries? Once I figure the actual wiring out, I may move the two 6 volt batteries to definitely be the house power and one of my starter batteries back to the Onan to pop it off. All to be determined... 
Hopefully, that won't be an issue for long. That stock AC is coming out! A Vintage Air Gen 4 will replace it, with automated controls from Dakota Digital
What you have is NOT standard OEM for a 1973 coach. The arrangement changed on later coaches. So you need to try and figure out what you have now. It is not necessarily bad. In 1973 you had both the house and engine starting batteries up front with a very little Onan starting battery in the rear. In later years 1975 or 1976 they moved the house battery(s) to the rear and gave you the capability to have large ones back there. They also threw away the starting battery and then started the Onan on the large rear house battery. It sounds like you have a cross between the two designs. I can not tell you how someone set it up to charge those added rear batteries. They may have added a combiner or just slapped them in parallel with the front which is a bad idea. Also you need to figure out what house stuff is running on the front VS. the rear house batteries.One of these days, I'll have to dig into the manual that was provided to me for this coach. I've got two batteries up front, one off each end of the isolator. I've also got two batteries back by the Onan. They were big and beefy and probably 6 volt deep cycles wired in series. At this point, I'm not certain which are the house batteries. Normally, I would have assumed the batteries back by the generator were just to start the generator. But then why not a starter battery instead of two deep cycle 6 volts which were more commonly used as house batteries? Once I figure the actual wiring out, I may move the two 6 volt batteries to definitely be the house power and one of my starter batteries back to the Onan to pop it off. All to be determined...
Update!
New alternator installed. 15 plus volts out of the alternator and 14 plus volts on each leg of the isolator. Engine pops off just fine and runs smooth and almost silent. Although my choke appears to be stuck open at all times...
Batteries back by the Onan are definitely wired as house batteries. But so is the second battery up front on the engine battery tray. The Onan will start with no batteries wired in up front. The engine will not start off the batteries wired to the onan. So, the only crossover is the second battery up front that appears to also be wired into the house battery system. I'll eventually get everything isolated and figured out....
Thank you Kelvin for your much valued assistance and advice.
New alternator installed. 15 plus volts out of the alternator and 14 plus volts on each leg of the isolator. Engine pops off just fine and runs smooth and almost silent. Although my choke appears to be stuck open at all times...
Batteries back by the Onan are definitely wired as house batteries. But so is the second battery up front on the engine battery tray. The Onan will start with no batteries wired in up front. The engine will not start off the batteries wired to the onan. So, the only crossover is the second battery up front that appears to also be wired into the house battery system. I'll eventually get everything isolated and figured out....
Thank you Kelvin for your much valued assistance and advice.
Sounds like good progress! Good to hear.Update!
New alternator installed. 15 plus volts out of the alternator and 14 plus volts on each leg of the isolator. Engine pops off just fine and runs smooth and almost silent. Although my choke appears to be stuck open at all times...
Batteries back by the Onan are definitely wired as house batteries. But so is the second battery up front on the engine battery tray. The Onan will start with no batteries wired in up front. The engine will not start off the batteries wired to the onan. So, the only crossover is the second battery up front that appears to also be wired into the house battery system. I'll eventually get everything isolated and figured out....
Thank you Kelvin for your much valued assistance and advice.
Question/opinions on brakes (if I upgrade to all disc brakes)...
Topic one:
I've been reading about the "reaction arm" brake modification system and the benefits in terms of emergency stops, wear on tires, etc. If I'm reading correctly, there may be three individual systems currently available:
).
Topic Two:
Electronic Parking Brake
This appears to be a motorized caliper that attaches to one of the wheel pairs on the bogie. To verify; this is a second caliper; it doesn't replace one of the other calipers? Any issues interacting with the reaction arm system? I wouldn't expect it to affect the actual braking, but how about the system mounting, etc.?
16" Wheels:
Will any of these upgrades (including the larger calipers used in the upgraded disc brakes) cause fitment issues with the ION aluminum wheels from GMCRVPARTS? From my reading, it appears those are the only "hub-centric" wheels other than the original 16.5" steelies; I could get them at a bit of savings from Discount Tires, etc., but those are not hub-centric(?).
I'm quite possibly misinterpreting some of what I am reading, as I have limited experience with braking systems, and none at all with a bogie (no nose jokes). Any modifications will be handled either at a shop or under the supervision of someone more experienced.
If I am interpreting what I am reading correctly, I will also be adding a powered vacuum assist (perhaps a storage tank as backup), a larger brake-booster, a different proportioning valve, and a larger master-cylinder. Of course, if I'm doing all of this, I should update the brake lines as well.
Also, can I do these upgrades in stages?
Thoughts? Thank you!
Topic one:
I've been reading about the "reaction arm" brake modification system and the benefits in terms of emergency stops, wear on tires, etc. If I'm reading correctly, there may be three individual systems currently available:
- Chuck Aulgur
- Manny
- GMCRVPARTS.com
).Topic Two:
Electronic Parking Brake
This appears to be a motorized caliper that attaches to one of the wheel pairs on the bogie. To verify; this is a second caliper; it doesn't replace one of the other calipers? Any issues interacting with the reaction arm system? I wouldn't expect it to affect the actual braking, but how about the system mounting, etc.?
16" Wheels:
Will any of these upgrades (including the larger calipers used in the upgraded disc brakes) cause fitment issues with the ION aluminum wheels from GMCRVPARTS? From my reading, it appears those are the only "hub-centric" wheels other than the original 16.5" steelies; I could get them at a bit of savings from Discount Tires, etc., but those are not hub-centric(?).
I'm quite possibly misinterpreting some of what I am reading, as I have limited experience with braking systems, and none at all with a bogie (no nose jokes). Any modifications will be handled either at a shop or under the supervision of someone more experienced.
If I am interpreting what I am reading correctly, I will also be adding a powered vacuum assist (perhaps a storage tank as backup), a larger brake-booster, a different proportioning valve, and a larger master-cylinder. Of course, if I'm doing all of this, I should update the brake lines as well.
Also, can I do these upgrades in stages?
- Vacuum, booster, master-cylinder
- Discs (keeping in mind the sizes needed for the other systems in the future)
- EPB
- Reaction Arm system
- Wheels (if needed)
Thoughts? Thank you!
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Luther,
So many questions so little time, (or money).
Topic one:
I've seen video, I've read descriptions, I think I understand the physics. Great idea in my opinion. Were I to start over again I might do that first, but actually I have no experience. So I don't get to comment.
Topic two:
On my '73 the parking brake workings were totally corrodded so I cut them off when I installed disk brakes. I have no parking brake and mercifully live in a state that doesn't care. After living for many years in Duluth, MN which is one big hill I have tricks for parking on an incline and chocks if I can't use tricks. I'm careful not to challenge the parking detent in the transmission.
Topic Three:
I bought a set of Ion alloy wheels from JimK(Applied) after I had bought a four bag suspension AND the six wheel disk brake conversion from him. I did the four bagger first, after I lost the drivers side OEM air bag at 70mph. The installation was done on the concrete floor of a barn and took 2 days. Slight modifications were required due to some novel brake line routing on my particular '73. I could not detect any difference in ride from the OEM bag system when driving, but appreciate six wheel independent suspension. I basically ignore speed bumps and "rough" railroad crossings.
I had already upgraded to a sensitized booster from Applied when I got an invitation to visit friends in the Black Hills. Knowing that I didn't want to take the stock brakes into mountains, I bought the six wheel disc kit from Applied. Installation was straightforward. Now, a severe stomp on the brakes will put any loose items in my lap at the front. I cannot imagine what a true "panic" stop would entail. I should note that in the motorhome, while I go fast, I am a conservative, defensive driver with my attention well ahead of my location.
Finally, I bought a set of Ion alloy wheels (also from Applied) and put on a set of Cooper HT3's with five ounces of Airsoft beads in each tire. I run at 61lbs in all tires (cold) with a TPMS, usually at 60-65 with forays up to 75mph, sometimes all day long. The ride is smooth, sweet and quiet. We LOVE to look at the world as it goes by in our GMC. Since our dash air is dead, we suffer through the air noise with wind wings and the toll windows open when it's hot. If we're going to be driving together for more than an hour, we use a set of soccer referee headsets (full duplex, no ptt, just on) to provide the high frequencies for our 75 year old ears.
To summarize:
From above you can see I have had no issues with compatibility or instalation. I think that may well be that I've use a single vendor. None of it was cheap. But I still have less in my wonderful coach that most of those I meet at campgrounds, and they're coming to me to admire my ratty old coach, not the alternate. Yes, you can do what you're thinking in stages. And follow the advice found many places on this forum, make it as safe as you can afford at the moment, and use it, use it, use it. Make it safer as you can afford, but never stop using it. The secret lies in the success the original builders had in making compromises that were wonderful. Start making wonderful memories now and that will make the money invested be money invested in joy.
So many questions so little time, (or money).
Topic one:
I've seen video, I've read descriptions, I think I understand the physics. Great idea in my opinion. Were I to start over again I might do that first, but actually I have no experience. So I don't get to comment.
Topic two:
On my '73 the parking brake workings were totally corrodded so I cut them off when I installed disk brakes. I have no parking brake and mercifully live in a state that doesn't care. After living for many years in Duluth, MN which is one big hill I have tricks for parking on an incline and chocks if I can't use tricks. I'm careful not to challenge the parking detent in the transmission.
Topic Three:
I bought a set of Ion alloy wheels from JimK(Applied) after I had bought a four bag suspension AND the six wheel disk brake conversion from him. I did the four bagger first, after I lost the drivers side OEM air bag at 70mph. The installation was done on the concrete floor of a barn and took 2 days. Slight modifications were required due to some novel brake line routing on my particular '73. I could not detect any difference in ride from the OEM bag system when driving, but appreciate six wheel independent suspension. I basically ignore speed bumps and "rough" railroad crossings.
I had already upgraded to a sensitized booster from Applied when I got an invitation to visit friends in the Black Hills. Knowing that I didn't want to take the stock brakes into mountains, I bought the six wheel disc kit from Applied. Installation was straightforward. Now, a severe stomp on the brakes will put any loose items in my lap at the front. I cannot imagine what a true "panic" stop would entail. I should note that in the motorhome, while I go fast, I am a conservative, defensive driver with my attention well ahead of my location.
Finally, I bought a set of Ion alloy wheels (also from Applied) and put on a set of Cooper HT3's with five ounces of Airsoft beads in each tire. I run at 61lbs in all tires (cold) with a TPMS, usually at 60-65 with forays up to 75mph, sometimes all day long. The ride is smooth, sweet and quiet. We LOVE to look at the world as it goes by in our GMC. Since our dash air is dead, we suffer through the air noise with wind wings and the toll windows open when it's hot. If we're going to be driving together for more than an hour, we use a set of soccer referee headsets (full duplex, no ptt, just on) to provide the high frequencies for our 75 year old ears.
To summarize:
From above you can see I have had no issues with compatibility or instalation. I think that may well be that I've use a single vendor. None of it was cheap. But I still have less in my wonderful coach that most of those I meet at campgrounds, and they're coming to me to admire my ratty old coach, not the alternate. Yes, you can do what you're thinking in stages. And follow the advice found many places on this forum, make it as safe as you can afford at the moment, and use it, use it, use it. Make it safer as you can afford, but never stop using it. The secret lies in the success the original builders had in making compromises that were wonderful. Start making wonderful memories now and that will make the money invested be money invested in joy.
If you are referring to Albert Branscombe's new EPB system, it is a single main + EPB all in one caliper. So there is only one caliper that does both and is mounted on the rear - rear wheels. The mounting for the caliper is different than the other GM calipers used on the rear, so it is not compatible with any reaction arm system.
Here is some info on his new EPB:
Electric Parking Brake for the GMC
My coach was the test bed for Albert Branscombe's Electric Parking Brake (EPB) for the GMC. The EPB uses calipers with a built-in motor for the parking brake function. We recently tested it to an incline of 15% (the maximum the dual piston...
www.gmcmotorhome.org
I have a one-ton front end which has 12.5" rotors rather than the OEM 11" rotors. This larger diameter gives the brake pads more mechanical advantage plus increased rotor area which the pads act upon. Both these factors, plus the larger caliper piston gives the one-ton front end substantially more braking power.
I also have Dave Lenzi's larger mid-rear axle brakes which give much better braking (same size as the one-ton disk)
This gives me braking like my new vehicles have.
You should decide what you want to do because each upgrade replaces some parts from previous upgrades. It would be cheaper in the long run to decide what you want in the end.
Indeed. Hence my questions; I don't want to do one upgrade only to find out that I have to undo it to do the next upgrade. If one upgrade negates the benefits of another upgrade, I wasted my money and time. It sounds as though, if I want electronic parking brakes, I can't have the reaction arm system. Or if I want the reaction arm system, I can't have electric parking brake. Is there another parking brake system that works with disc brakes on this coach? One person of my acquaintance indicated his preference would be to put discs on the mid wheels and keep the drums on the back wheels. Keep the cable parking brake on the back wheels. This also eliminates the possibility of the reaction arm system, but at least I get a parking brake with my rear disc brakes.If you are referring to Albert Branscombe's new EPB system, it is a single main + EPB all in one caliper. So there is only one caliper that does both and is mounted on the rear - rear wheels. The mounting for the caliper is different than the other GM calipers used on the rear, so it is not compatible with any reaction arm system.
Here is some info on his new EPB:
Electric Parking Brake for the GMC
My coach was the test bed for Albert Branscombe's Electric Parking Brake (EPB) for the GMC. The EPB uses calipers with a built-in motor for the parking brake function. We recently tested it to an incline of 15% (the maximum the dual piston...
I have a one-ton front end which has 12.5" rotors rather than the OEM 11" rotors. This larger diameter gives the brake pads more mechanical advantage plus increased rotor area which the pads act upon. Both these factors, plus the larger caliper piston gives the one-ton front end substantially more braking power.
I also have Dave Lenzi's larger mid-rear axle brakes which give much better braking (same size as the one-ton disk)
This gives me braking like my new vehicles have.
You should decide what you want to do because each upgrade replaces some parts from previous upgrades. It would be cheaper in the long run to decide what you want in the end.
Basically, I'm taking bits and pieces of multiple systems and trying to combine them into one cohesive system that meets all the safety needs and provides additional braking benefits (which is also a safety need). I have only one advantage; I can look at everything those who have come before me have accomplished and try to cherry pick the best solutions to incorporate.
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I believe the Cadillac parking brake calipers will work with the disk reaction system, but you would need to check with Manny or JimK on that.
The backup brake vacuum pump is a must have upgrade and I would get Dave Lenzi's system.
It was always said that you need a P35 master cylinder when using rear disk's, however Dave Lenzi disputes this. Albert Branscombe points out the rear disk brackets from sources other than him or Dave Lenzi will flex causing the caliper pistons to be knocked back, requiring more fluid capacity to apply the brakes. Using brake systems from Albert or DaveL means you can use the OEM mast cylinder which provides more line pressure.
The backup brake vacuum pump is a must have upgrade and I would get Dave Lenzi's system.
It was always said that you need a P35 master cylinder when using rear disk's, however Dave Lenzi disputes this. Albert Branscombe points out the rear disk brackets from sources other than him or Dave Lenzi will flex causing the caliper pistons to be knocked back, requiring more fluid capacity to apply the brakes. Using brake systems from Albert or DaveL means you can use the OEM mast cylinder which provides more line pressure.
Will the Caddy calipers hold the weight of the coach on an incline? I was reading somewhere that passenger car calipers just weren't up to the task of holding the additional weight of the coach. More precisely, there wasn't good data available on GM calipers to determine if they would be up to the task.
They are not! Which is why Albert came up with the EPB. They were more an answer to the requirement that a working parking brake be present. Not that the OEM parking brake could hold on much of an incline either!
So basically, it sounds like if I want good parking brake, I'm going to be doing without the reaction arm system. But, I guess if I get a good enough booster and good enough calipers, I can still get decent braking. So, it looks like the reaction arm system, while being an excellent idea, will not be getting installed on my coach. Unless of course, someone were to redesign it around the electric parking brake caliper instead...
Or, would it be possible to use the electric calipers on the front wheels only? Is that even a thing? Parking brake on the front wheels only?
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Have you driven it yet? I'm content with my brakes as designed, and my parking brake holds on a moderate hill just with the plain old hand brake lever.
I might eventually do big front brakes and a reaction arm system with rear drums, but I have plenty of other things to fix before then.
I'm used to towing, and the GMC on stock brakes stops better that my one ton truck towing 10-14k.
I might eventually do big front brakes and a reaction arm system with rear drums, but I have plenty of other things to fix before then.
I'm used to towing, and the GMC on stock brakes stops better that my one ton truck towing 10-14k.
I just today dropped the vehicle off at a service shop for evaluation to give me a list of all the repairs required to make it road safe. The brakes currently are terrible. Perhaps the system just needs an overhaul, but I've gotten used to disc brakes all the way around on all of my vehicles for the last 30+ years. Heck, even my bicycles have disc brakes.
Also (depending on the condition of the stock brakes), if I need a major rework of the braking system, why invest in drums when discs are an option? Provided the conflicting requirements can be resolved....
UPDATE!! (November 2023)
Famous last words...
When the vehicle was taken in for alignment, I lost my rear brakes. Apparently they had been leaking all along and I finally ran the master cylinder dry.... Since the alignment shop is also a brake shop, I had them check the braking system. They found all four rear cylinders were leaking and had to be replaced. Rather than open a new can of worms by installing rear discs, I just paid the money and now have good working rear drums again. Some day I may have rear discs....
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Me too. And I have done big brakes, rear Disc and full Disc conversions on several vehicles.
Disc brakes are obviously better, but even 4 wheel drums, when not neglected for decades, can lock up the tires.
Disc brakes are obviously better, but even 4 wheel drums, when not neglected for decades, can lock up the tires.
I wish Wally Anderson would write up an article on all the work he had to do to get 6 wheel disk brakes to work. It came down to the fact that there was not enough volume delivered by any of the commonly used master cylinders. With 6 wheel disk brakes his stopping power got worse. He ended up mounting a giant m/c off some bus or medium duty truck(?) , but it wouldn't fit behind the hatch, so he remote mounted it down behind the bumper. I real pita.
Wally is the sick genius that put MegaSquirt EFI on his Onan. He's extremely talented. He told me he wished he had stuck with the disc/drum combo and just added hydroboost with the original m/c.
Kelvin D. in Eugene indicated his 23' with disc brake system stops very quickly. I believe he said the biggest improvement was the installation of the larger vacuum boost (I really should pay more attention to off-the-cuff comments). I'll be picking his brain once I get to that point.
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