Coast Resorts Open Roads Forum: How many of us are there? Owners of Dodge based RV's?

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Topic: How many of us are there? Owners of Dodge based RV's?

Posted By: Griff in Fairbanks on 08/28/15 07:46pm

Assuming Jerry has solved the first part of his problem -- finding the little bugger (i.e., coolant temp sensor), let's try to solve the second part -- getting the temp gauge working.

Instead of just addressing his problem, I want to take a more general approach on the assumption other people will run into similar problems.

This will require several posts, as I take time to gather information and write the posts while taking breaks from other stuff. (Such as getting things ready for winter ... which will be here in a few weeks or a month.)

Most of our older motorhomes have four gauges: Fuel Level, Oil Pressure, (Engine) Coolant Temperature, and Electrical Ammeter. The first three operate in a similar fashion and the same basic problems and troubleshooting techniques apply to all three. The fourth (Ammeter) is an evolutionary holdover who's operation is an anomaly compared to the first three.

I will be focusing on the first three because of their similarities and ignoring the fourth because of it's significant difference. (Also, I consider ammeters to be functionally outdated, an opinion I will explain if anyone's interested.)

The following is oversimplified diagrams of basic gauge circuits. The top circuit demonstrates the basic wiring of gauges in older vehicles, such as most of our motorhomes. The bottom circuit reflects that found in newer computerized vehicles.

[image]

Note: Leeann may recognized this diagram. It's part of an article I started writing several years ago but haven't (yet) gotten around to finishing. (Back then, Leeann helped me with proofreading and editing what I've gotten done so far.) Also, this diagram is copyrighted by me and may not be used without my permission.

Missing from this diagram is a voltage regulator between the +12v and the gauge. Most gauges operate on nominal 5 volt current, which is an apparent technological holdover from the days of 6 volt automobile electrical systems.

In most older vehicles, a single voltage regulator (which is often referred to by other names) serves the fuel, oil, and temp gauges. This regulator is usually mounted on and wired into the instrument cluster.

Aftermarket gauges have a voltage reducer/regulator built into the gauge itself so it can be simply wired to +12VDC supply.

The gauges themselves are actually just voltmeters, displaying voltage levels ranging from zero to five volts.

The sensors, in turn, are variable resistors which vary the amount of current (voltage) in the circuit based on whatever they're monitoring.

When the fuel level/oil pressure/coolant temperature is low, the sensor increases resistance in the circuit. This causes the voltage to drop to near zero and the gauge needle to remain towards the left side. As these conditions rise, the sensor resistance drops, allowing more voltage into the circuit and causing the needle to move to the right.

At this point, you're probably thinking, "Jeez, this is simple." Well, you're right. It generally take me less than an hour to find and fix gauge problems and sometimes a little as five or ten minutes.

I have a good idea as what Jerry's problem is but I prefer the "teach a man to fish" approach.

BTW - there's been a revision to that saying ... "Give a man a fish and he'll eat for a day. Teach a man to fish and he'll sit in a boat all day drinking beer."

I'll stop here temporarily while I go do other things. When I take another break from those other things, I'll describe what can go wrong with gauge systems and how to find the problems.

(Yes, I will get back to starter vs deep cycle batteries eventually. However, Jerry's problem presented an opportunity to take a break from that and look at something that's simpler.)

1970 Explorer Class A on a 1969 Dodge M300 chassis with 318 cu. in. (split year)
1972 Executive Class A on a Dodge M375 chassis with 413 cu. in.
1973 Explorer Class A on a Dodge RM350 (R4) chassis with 318 engine & tranny from 1970 Explorer Class A

Posted By: Griff in Fairbanks on 08/29/15 06:10pm

Note: The 5 volt instrument regulator used to be (and sometimes still is) called a voltage limiter, which served to differentiate it from the 12 volt alternator regulator. To avoid confusion, I will use limiter from now on.

On OEM gauges, the fact one limiter serves the three gauges represents a single point of failure. If the fuel, oil, and temp gauges are all operating erratically or fail to operate, the instrument limiter is probably the cause.

In this case, the limiter may have gone bad or its +12VDC supply may have been broken. Identifying the cause of the malfunction typically requires removing the instrument cluster from the dash, which can be a bit of a PITA.

Instrument voltage limiters tend to be fairly durable so a broke +12VDC supply is a more likely cause. A loose or disconnected +12VDC supply at the instrument cluster should be relatively obvious. Less obvious causes could be a blown fuse or circuit breaker, broken supply wire, or disconnect at the other end of the supply wire.

Use a 1156 bulb and socket, two alligator clips, and a length of 16 gauge wire to make a continuity tester. (You could buy a continuity test but the wire leads on these are often too short to test all circuits.) You can connect one end to a known ground but I usually just attach one of the alligator clips to the battery's negative terminal. Connect the other end to the instrument voltage limiter. If the bulb glows brightly, you have a good +12VDC supply. If the bulb glows dimly, you've found the +5VDC side of the limiter and it's associated wiring.

Two notes: (1) The ignition key must be in the run position for the above test to work. (2) If the bulb glows dimly, your limiter is working and your problem is elsewhere.

I'm going to take a break here to go get some other things done. When I come back, I'll continue gauge troubleshooting and repair.

Posted By: my440 on 08/29/15 07:09pm

Griff in Fairbanks wrote:

PoorGary wrote:

Need to find brake pads, rotors, calipers for 1978 Dodge Sportsman.
Have not made any attempt to locate parts as of yet.
Was wondering if anyone on here has had a hard time or easy time hunting these parts down.
Thanks

2 CQ DRUMS & ROTORS YH141089 BRAKE ROTOR 1978 Dodge CB300 5.9 L, 360 CID GAS
1 CQ FRICTION GMD269 BRAKE PAD SEMI-MET. 1978 Dodge CB300 5.9 L, 360 CID GAS
1 INTERNATIONAL BRAKE INDUSTRIES 5516A DISC BR HDW KT 1978 Dodge CB300 5.9 L, 360 CID GAS
2 AUTOMOTIVE HARDWARE 13938 CONNECTING BOLT 1978 Dodge CB300 5.9 L, 360 CID GAS
2 DORMAN 484-185 BRAKE HOSE WASHER 1978 Dodge CB300 5.9 L, 360 CID GAS
1 CARQUEST Calipers 18-4076S Friction Ready Caliper w/Installation Hardware - Reman 1978 Dodge CB300 5.9 L, 360 CID GAS
1 CARQUEST Calipers 18-4075S Friction Ready Caliper w/Installation Hardware - Reman 1978 Dodge CB300 5.9 L, 360 CID GAS
2 Brake Hoses SP5586 1978 Dodge CB300 5.9 L, 360 CID GAS
2 CARQUEST Premium Bearings A35 1978 Dodge CB300 5.9 L, 360 CID GAS
2 CARQUEST Premium Bearings A37 1978 Dodge CB300 5.9 L, 360 CID GAS
2 CARQUEST Premium Bearings 15101 1978 Dodge CB300 5.9 L, 360 CID GAS
2 CARQUEST Premium Bearings 15245 1978 Dodge CB300 5.9 L, 360 CID GAS
2 CARQUEST Premium Seals 493291 1978 Dodge CB300 5.9 L, 360 CID GAS
2 Dorman HELP! 05190 1978 Dodge CB300 5.9 L, 360 CID GAS

Included parts you may not need, just in case you do. Included brake flex hoses in case yours are cracked or checked. Included bearings and wheel seals because I prefer to replace seals and check/repack/replace bearings as long as I'm working on the front end.

I assumed you have the 4,500 lbs front axle. Didn't crosscheck to see if parts are the same for 4,000 front axle so you may need different bearings, etc.

CB300 chassis should be same as MB300 chassis.

CarQuest part numbers ... other retailers should be able to cross-reference those numbers.

This is the best I can do but is not guaranteed to be correct. Motorhomes are often neglected or listed incorrectly in parts databases.

I recommend flushing your brake lines before bleeding the brakes.

Sorry for the delayed response. I much appreciate your parts number list which I printed and showed the parts dealer guy. He said no worrys he has all that info on his end. All parts I need where available. I was pleasantly surprised as I figured ordering parts for a 37 year old vehicle was going to be a nightmare.
Thanks Griff

Posted By: Griff in Fairbanks on 08/29/15 07:50pm

PoorGary wrote:

You're welcome, I'm glad I was able to help and make your task easier.

Yes, it's surprising the number of parts stores have in stock or can receive quickly when ordered. When I worked at CarQuest, we sometimes had parts in stock for 50 and 60 year old vehicles, much to the customer's surprise. (Back then, a lot of vehicles used the same parts so stores don't have to stock too many parts to service them.)

Posted By: regis101 on 08/29/15 08:12pm

I was almost going to start a new thread since I'm having trouble with my inquiry.
I'll ask here since the issues just came up.

I am also browsing around for front and rear shocks and brake parts. Pretty much everything seems available. But I'm having trouble telling what chassis I have vs the listed axle weights. Should be simple though I would think?

I have the mfg tag on the door and it states, 3300# front and 5700# rear. GVW as mtg'd is 8300#. The rear has duals and the front is a single 8 lug typical one ton type wheel, with dog dish hub cap, not a dually style wheel.

So far, Bilstein seems to be the only one to address the 4k# or non-4k# regarding shocks. I use AutoZone as my go-to FLAPS just because. Their website description(s) can be sometimes no accurate enough for me.

Am I thinking too hard? The B30, B300, CB300, MB300 is spinning me around

Just came from AutoZone website. Looked at front wheel bearings. Looks like the 3000 and 3300 lb fronts are 5 lug. 8 lug lists higher weights than my door tag.

http://www.autozone.com/suspension-steer........00-1-ton-van/1973/8-cylinders-f-5-9l-2bl

* This post was edited 08/29/15 08:23pm by regis101 *

Peace. ~RL

Posted By: Griff in Fairbanks on 08/29/15 08:52pm

regis101 wrote:

B30 is either a typo or something completely different, so ignore it.

Yours is an MB300, with the M meaning motorhome.

The CB300 is virtually identical to the MB300, with the C meaning commercial (i.e., box van). Both are "cut-away" chassis delivered incomplete to secondary manufacturers for use to build a variety of motorhomes and commercial vehicles.

(Apparently, Mother Mopar came up with the "M" designation because some people had hiccups over their fancy motorhome being built on a "commercial" chassis ... Mother Mopar might have better using a "heavy-duty" designation for both, such as H300.)

B300 is simply the complete 1-ton van.

Outside of the body/coach/box, all three are essentially the same in terms of engine, drivetrain, and chassis, with similar variations across all three "models". That means the same parts fit all three, taking into account variations such as front axle weight rating.

Okay, just saw your edit. Because yours has eight lug wheels on the front, stay with the that axle rating.

I haven't much luck with Autozone, as well as other common parts stores. Their business model is heavily oriented towards cars and more common light trucks (i.e., pickups and vans). Their listings for our vehicles tend to be sparse and I've found lots of errors in the few parts listing they do have.

CSK/Schuck's tends to be middle of the road, between few erroneous listings and full appropriate listings. NAPA and CarQuest tend to be better, especially if the particular store caters to commercial trucks and/or has knowledgeable counter people.

When it comes to shocks for older motorhomes (actually all motorhomes), finding the right shocks tends to be a PITA. Shock manufacturers tend to focus on newer vehicles and, while they may have appropriate shocks for older vehicles, they've ceased listing those applications. Generally, you need a parts person who really knows what their doing and, especially, have hung onto the old PAPER catalogs.

I've had the best luck finding shocks through KYB. If you have the old shocks, see if you can find a part number. Also, see if you can find the Dodge chassis VIN on the outside of the frame behind the right front wheel. Many motorhomes have two VIN tags, with different numbers ... one assigned to the chassis by Dodge and the other assigned to the whole vehicle by the coach manufacturer. (Thank Congress and the bureaucrats for that SNAFU.)

In any case, send me the old shock part number, chassis VIN, and any other info you can find in a PM and I'll try to track down a source for the right shocks.

Posted By: Griff in Fairbanks on 08/29/15 09:19pm

By the way -- shock technology and manufacturing has come a long way in the last 30 or 40 years. Appropriate replacement shocks may not look anything like the old shocks currently on your motorhome. (The replacement shocks for my RM350 is considerable smaller in diameter than the original shocks.)

Also, your door tag may be incorrect. In particular, if the door was replaced, it may have a tag for a B300 with a lighter weight front axle. This is why I consider the chassis VIN vital to finding the right parts.

Posted By: Jer&Ger on 08/31/15 08:20pm

Hi Griff, Yes I found it and I hope I don't have to replace it. My big hands will never get at it. The wire is on it too by the way. I'll read your post on figuring out what's wrong now. I had to replace the front brake pads and have found out that my master cylinder is letting fluid bypass, so I'll have to replace it too. That's what I've been working on for the last few days. I'm hoping to be able to use it this weekend, so I'm crossing my fingers.

Jerry & Gerry, our pets (dogs), Byron, Coco
1976 Monaco, 440 ci. Dodge Sportsman chassis

Posted By: regis101 on 08/31/15 09:46pm

I also use RockAuto. Browsed their site. Was able to narrow things down by eliminating the obvie. I'm still gonna have to do bit of reverse engineering for my mind to make right. No harm. No foul. I'll pull a front wheel, front shock, and rear shock to take dimensions of pertinent components. It is what it is. I've been finding parts for the '72 also that make better sense. blah blah. Such is life working with forty year old vintage iron while living in a parts-is-parts world .

Posted By: Griff in Fairbanks on 08/31/15 10:21pm

regis101 wrote:

The calipers and rotors may have casting numbers that can help find the right parts ... especially when there's no catalog listing.

Bearings and races have numbers on them that are also most reliable for finding the right parts.

in a few cases with shocks, it may be necessary send one of the old shocks to knowledgeable people to find the correct replacements, using measurements, etc.

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