Technical Inquiries: April 2002

Fan Switch
Q: I own a 1995 Safari Trek on a Chevrolet P-30 chassis. In the November 2001 issue, the “Technical Inquiries” column included instructions for adding a manual switch to the radiator fan control on a P-30 chassis (page 24). Please explain why a manual fan control is desirable.

Gordon Bawden, F281944
Seattle, Washington

A: The manual switch described in that column overrides the thermostatic switch that normally turns on the electric radiator cooling fans when the hot air-conditioning refrigerant flowing to the condenser reaches a certain level. The manual switch allows you to anticipate conditions when more cooling may be needed “” such as on long hill climbs “” and react accordingly to turn on the electric fans whenever desired. This is especially useful when the air conditioning is not being used or when the refrigerant temperature is not hot enough to turn on the A/C temperature sensor switch, which will still operate normally with the manual switch installed. Properly used, the manual switch can provide a significant boost in cooling airflow under all conditions.
“” E.P.

Q: I own a 1989 Pace Arrow motorhome with a Chevrolet 454 engine. It has approximately 42,000 miles on it. In 1999 I had all new spark plugs and wires installed. In 2000 I started having difficulty with the engine backfiring and shutting off. While I was driving, the engine would stop running. If I let it sit for about two hours, it would restart. However, after the engine warmed up again, it would quit running. I drove the coach to a repair shop, and it was determined that the new coil that had been installed was causing the problem. After the coil was replaced, I drove the coach home and did not drive it very much until recently.

The coach started backfiring again just as it did before. In Louisiana, we do not have many high grades, but every time I drove up a slight grade, the engine hesitated and backfired. I changed the fuel filter, but the performance did not improve. Our last trip was less than 100 miles each way, and most of the trouble occurred on the way home. Do you have any idea what the problem could be?

We love to travel and belong to an RV club, but we have remained home most of this year, because we do not trust the coach.

Ronald Hungate, F122109
Bossier City, Louisiana

A: I have some questions, and a few more details would have helped determine whether this is a fuel problem or an electrical problem, since the symptoms could fit into both categories. The 1989 Chevrolet 454 engine would have an onboard computer “” did anyone read the codes? Even though this version of the computer was used primarily for storing emission system failures, the readout could provide a valid tip.

When you replaced the fuel filters, did you replace all of them? You could have as many as three: a filter in the fuel tank, a filter in the engine compartment, and possibly a chassis-mounted filter under the coach (often in the area of the steps). If the problem occurs mostly on hot days, it could be a case of old-fashioned vapor lock.

When you say that the “new coil was replaced,” was it the HEI ignition coil located in the distributor cap or the magnetic pickup coil in the body of the distributor?

Those questions being asked, here’s my guess, and it’s based on occasions when I have experienced these identical symptoms on two different coaches. The problems were caused by a faulty ignition module (also known as the magnetic pickup coil), which is located in the body of the distributor. When this module reached a certain temperature level, the faulty coil would either send an erroneous signal to the distributor, causing backfiring such as you have experienced, or it would send no signal at all and the engine would quit. When this occurred, the engine would not start until the module cooled. I hope that this proves to be your problem, since it’s a relatively easy and inexpensive fix. By the way, I would recommend that you use the OEM Delco replacement part.
“” E.P.

Q: We recently purchased a new Winnebago Adventurer motorhome on the Ford chassis with the Triton V-10 engine. It is now due for its first oil and filter change. I was surprised to find that Ford specified SAE 5W-30 as the recommended oil viscosity. Can this be correct? There are no other summer weights versus winter weights listed. My experience with previous motorhomes (five in all) was that SAE 10W-30 weight oil was marginal, and the manufacturers always recommended SAE 15W-40 for heavy-duty applications such as motorhomes. Some years back the engine manufacturers recommended SAE 10W-30 oil for their engines because of corporate average fuel economy (CAFE) requirements, but they really didn’t want you to use such light oil in heavy-duty applications. What is your recommendation?

Bill Heger, F54026
Hot Springs, Arkansas

A: Always follow the recommendations found in the vehicle owners manual. Ford has tested these engines extensively and has determined that SAE 5W-30 (SAE 5W-20 in later models) is the best for the Triton V-10 engine. The engine’s clearance tolerances are very tight and need the lighter weight oil for proper lubrication and cooling. In addition, the now-required SAE 5W-20 premium synthetic blend oil reportedly provides better protection of internal engine components and will increase fuel economy by an average of 0.6 percent (0.14 mpg).
“” J.B.

Q: I am trying to determine whether my 2001 Nissan Frontier four-wheel-drive truck with automatic transmission is towable out of the box or whether it needs a tow package installed. I have consulted the vehicle owners manual, which doesn’t reference recreational towing; called Camping World (they referred me to Remco, the towing package manufacturer, which says no package is necessary, as my vehicle has a neutral position on the transfer case shift lever); and called my Nissan dealership (they seem unsure).

As it is a new vehicle, I’m uncomfortable installing a towing package that may void the vehicle’s warranty and possibly incur future additional cost. However, I’m also afraid of towing the vehicle as is if it will be ruined.

Scott Grant, F303378
Yamhill, Oregon

A: As an FMCA member, you have access to the March 2001 “Towing Four Wheels Down” article via www.fmca.com. (It can be found in the “FMC Magazine” section of the Web site. To access the article, FMCA members must log in.) That article lists the information provided to FMC magazine last year when we conducted the survey of vehicle manufacturers and asked about towing four wheels down behind a motorhome. At that time, Nissan officials indicated that the Frontier 4×4 Crew Cab with a manual transmission was towable four wheels down by placing the transfer lever in “2HI.” However, the company did not indicate that the Frontier equipped with an automatic transmission was towable without modifications. (They did indicate that after towing 500 miles, all Nissan vehicles should be stopped, placed in neutral, and idled for several minutes to circulate the fluids.)

Q: I have been towing a 1994 Saturn SL1 for quite awhile now using a Roadmaster Falcon 5250 system. I’ve had great success during some 30,000 miles of towing, in part due to the assistance of Family Motor Coaching magazine.

Due to the age of the car, we purchased a new 2002 Saturn L300. I am having the appropriate EZ Lock brackets mounted on this car so I can continue to use my Falcon towing system.

Okay, now for the question: The 2002 Saturn owners manual says to remove two fuses before towing the car. Can you explain why this needs to be done? Is it for long trips, overnight only, or 100 percent of the time? Is this only for battery discharge, or is there an ignition overheating concern? I have never pulled any fuses on the 1994 Saturn and have never had any problems. Have I been wrong here, too? We plan to keep both cars available for towing.

I have been an RVer since 1962. We pulled travel trailers for many years, but have converted to the motorhoming experience with a 2000 40-foot diesel pusher. We are fortunate, still being in our 40s, to be creating family memories with our children in such luxury.

Doug Jozwiak, F271822
Berkley, Michigan

I’m a rather new RVer, a new member of FMCA, and I need some advice. I intend to tow a 1994 Saturn SL2 with an automatic transmission. Can I tow it four wheels on the ground without any modifications to the vehicle?

Glenn Larson, F300364
New Carlisle, Indiana

A: Saturn was the first automaker to endorse towing of its vehicles with automatic transmissions four wheels down without the need for modifications. Later models require that one or more fuses be pulled before towing to avoid draining the battery. This requirement was first brought to our attention starting with the 2000 model year, so the 1994 models would not be involved. However, all Saturn owners should check the vehicle owners manual and follow its recommendations.