NEED ADVICE AND STRANDED...kinda - PeachParts Mercedes-Benz Forum

DJNEWK2 · #1 11-06-2008, 03:26 PM

I have an 83 300SD with 180k and just took her on a road trip (only about 120 mi) and found that once I was a little over 15 minutes from my bud's house the windows would sometimes roll up slower than normal then return to normal speed but didn't think about it. I got here and parked in his driveway to unpack and was inside all of 5 minutes with my parking lights still on. Came back out to move the car so we could situate the parking spots so no one was blocked and access out (as my bud was commenting on how nice the car is and ME stating that she's a tank I've NEVER had a problem with in 5 years) I turn the key and "click" with a moan under my side (turned out the noise was the glow plug relay). Like I said, this had NEVER happened and have driven this girl all over the place and looking online I see a few others had this problem and don't know what it was either but she started right up with a jump (I have the portable jumper for the lighter,air pump etc,whew!) and its a new battery anyway along with all new belts and alt is fine.

Of course my buds here kept saying to replace the battery, the alt, the voltage regulator but I basically ended up doing an experiment before replacing any of those (and since I'm here for a week or at least WAS cause I'm leaving to go home tomorrow) beginning with unplugging the relay (after it glows on the dash and goes off and its running) and letting it get up to temperature to see what happens and we all put her on the road as he followed me and I turned on brights,windows rolled up normally, no dimming at all when switching on anything (this was at night so I could really tell) but she stayed just perfect. The next night we did the same thing with the relay connected and sure enough after about 20 minutes we could tell with the windows,lights dimming (my bud says he could see my headlights fading in his rear view) and then my radio went out as I drove.

After a while I couldn't see my lights (euros) on the ground which makes me think they started to look like I had em on what my buds called the cool "phantom" look selected but it was on brights! After getting out and disconnecting the relay and letting her run a while the charge went back up to where I could get her back to my buds. I couldn't understand why its acting up but I DID replace all glow plugs and remember that ALL but one plug were bad and I would always have kinda hard starts since I started driving her a lot lately the past 2 months or so but she'd start because I had her in the garage and block heater plugged up. She's started right up since then but I'm confused because the relay would come on the dash and go out but I'd been recently convinced that the relay must've stayed on and burned them all out all this time and since I had no working plugs the draining just didn't occur. Now that I have a fresh set of glow plugs (and it was literally like 3-4 days before I came here that I changed them out) the relay has its current along with the plugs draining more than the alt can handle. So far I just start her up and I've been just letting her run a while and shutting her down since most of the sightseeing has been with the guys and they've driven so no big deal. MY QUESTION is will there be damage to her if I do what I want to do which is to use the relay to start her up and let her run for the 3 minutes with the relay like it's supposed to and disconnect it and just drive her home (where I have a spare relay waiting anyway) or shell out $170 for a new one to be delivered here? I've never had to do this and it worked out fine driving around here 5-10 miles but I'm thinking it should be no different for her to roll back home 120 miles to the garage to swipe the relays out... The little woman's scared to death but I wanna assure her we SHOULD be fine but I also want to be sure I'm not doing damage to my faithful "other" girl

Thanks in advance

300SD81 · #2 11-06-2008, 03:32 PM

Sounds like your glow relay is not turning off. I'm pretty sure the plugs stay on for a while even after the dash light goes out, so thats no indication of it actually turning off. No reason you shouldn't be able to drive her home, glow plugs are only used for starting...

kerry · #3 11-06-2008, 03:34 PM

Unplug and driver her home. No problem.