Strange Smell in Cockpit

[Vectra04]

Dear Forum Readers,

We have a 2004 Winnebago Vectra 40 AD with a 350 Cummins Diesel. The motor coach has been a joy to own (besides the usual technical issues); however, there is a recent happening with the motorhome that has us concerned--we are hoping someone on this forum has dealt with the same issue!

A few weeks ago, after backing into our campsite following a 6 hour drive time, we smelled somewhat of a burning smell coming from the dash AC, as well as the left side cockpit controls where the transmission touch pad changer is. Though the smell lingered for a good while, we thought it originated from the mirror heat that was accidentally turned on when backing the RV into the campsite.

A week later, when leaving for the return trip home, we drove the RV from the campsite to the gas station (approximately 15 min), and upon pulling into the gas station, the same overwhelming burning smell (I would like to describe the smell as that of burning plastic with a hinge of caustic sweetness to it) appeared once more from the dash air. A fellow RVer parked at the pump next to us said he felt there must be something wrong with the HVAC unit...further, upon calling Camping World in our home city and describing the smell, they felt that it could possibly be a freon leak.

When we returned home, we took the motorhome to Freightliner--we have a great relationship with them and they always go above and beyond when taking care of the coach. They disassembled and reassembled the HVAC system, not really finding any cause of the smell. Further, they checked the whole coach over as part of a regular service, and still couldn't find any source for the smell...there were a few things that needed fixing, including the blow-by tube and replacing the power steering filter, etc.

When Freightliner released the RV to us, we took it on a short trip (1 hour driving time) to test it out...well, guess what? The same smell is back. After driving an hour without any notice of the smell coming from the front AC, we backed the Vectra into the campsite, and as the coach was idling, the burning smell started coming from the AC...this time only from the far left vent and the left side control panel. A fellow RVer described the smell as that of a chemical smell. The RV is about to go back to Freightliner...but, has anyone ever experienced this before??? ANY help will be much appreciated!!!

[trackman]

Check all batteries. Could be acid smell from hot battery

[Vectra04]

Thank you for your help! We checked the batteries, and they are all fine. However, upon further inspection of the cockpit area, we noticed remnants of the smell on the floorboard from around the gas and brake pedals...

[emiddleb]

Guess I'd start trying to narrow it down by what you are doing when the smell hits and what you have running. Seems like from your comments it only happens when you have driven for a while, so I'd be looking at chassis systems versus house systems as a start.

Might look up under the dash for any wires that appear cooked. Were you running the gen during your trips? It's right under your driver area. Running air? Dash heater?

Under the driver footrest plate on the upper left of the floor is a cutout compartment with a lot of cables (you need to feel for the screws in the carpet at the base of the slanted plate to remove it.) Anything fried in there?

How about the front wheels/brakes/tires after driving? Are they extraordinarily hot?

You can remove the dash top. Screws along the window edge, some across the top, and as I recall you need to start with the side panel to the right of the radio, then the small top panel, then finally the one in front of the driver. Then you can look for hot wires etc. Since you keep saying the smell is from the AC vents I'd check the vent hose/tubes for breaks or anywhere an odor could get into the system from somewhere else.

Try the various systems (headlights, mirror controls, etc) and see if any of them are not working properly (shorted) or if leaving any of them on for a time causes the smell to return.

Just some thoughts...

[ruffian]

The most common "chemical smell" I have found in the cockpit area, discounting burning electrical wires, has been a strong "sweet" odor caused by anti-freeze leaking from the dash heater.

May not be your problem but a good place to start looking. A couple drops of engine coolant under the dash can really stink up the place.

Easy to smell old anti-freeze to see if it smells like your problem.

Good Luck

[bob109]

You mention you had your unit to a Freightliner facility so I'm assuming you have a Freightliner Chassis. That said, I'd like to share with you my experience with the "burning plastic smell with a bit of caustic sweetness".

Had a friend visit for a few days and on a rainy evening he was sitting in the drivers seat which I had rotated to face the living area of my Discovery. While sitting in the seat he had his arm rested on the steering wheel and unbeknown to both of us his arm was pressing on the "horn bar". As there was no air pressure in the system the horn never sounded although the "Air Horn Solenoid Valve was activated continuously for over 20 minutes. This fried the valve and we smelled something burning and entering the dash area through the dash vents. I never found the burned wiring and valve until the next day. The valve is located on the outer firewall directly above my Onan Generator.

I was able to buy a new valve at a local Freightliner Dealer. The cost, as I recall, was $42.50. Removing the old valve and installing the new one took 15 minutes.

I didn't sleep well the night the incident occurred and will never forget the distinct smell of the burning valve.

Check and see if your air horn is working and the condition of the valve.

[Billy S]

Have you looked at all the relays, wires, fuses in the compartment on the left front outside compartment under the driver? Behind the fuse panel there are bundles of wires and more relays, the turn sign and emergecy flasher are wrapped inside a wire bundle. Good luck, Happy Veterans Day

[toneumanns]

I sometimes have a strange smell in mine also...............I always tell the DW it's not me. SPD's may be the cause. Just sayin.

[Vectra04]

Thank you all for your comments, they have been of great help! We just returned from road-testing the vehicle with the Freightliner technician to replicate the smell--indeed we were successful. After driving the vehicle about an hour, and placing the unit in reverse as if we were backing into a campsite, the smell returned. We removed the footrest and isolated the smell to the wires there. Further, upon opening the front driver side compartment where there is access to those fuses, wires, etc, the smell was noticed. Thus, at least we have narrowed down the general location...the technician said it smelled like overheating wires...the challenge now is finding out exactly which wire or relay could possibly be causing the problem.

[garykk]

I would venture a guess that the main feed to that panel is corroded or loose..

[porschegino]

We have a 2005 Tiffin Phaeton. When the dash fan is on and I brake (easy or just a little) we get a diesel smell thru the vents. It goes away pretty quickly but is giving the wife a headache. Just to check, I turned off the dash fan and then braked. No smell. Any ideas?

[motohomer]

Overfill recently?

[porschegino]

We had the motor home filled but only about 3/4 full.

[DieselTech39]

Fuel cap on the filler tube??