Thanks much. It was bad ground. Michael E. Esh
On Apr 27, 2019, at 2:36 PM, fmiser via Mercedes <mercedes@okiebenz.com> wrote: >> Michael wrote: > >> The most recent acquisition (84 300D) has an glow plug relay >> problem. I have replaced faulty plugs, tested wires for >> continuity, and replaced the relay with two different known >> good relays from operating vehicles. I cannot get the relay >> to kick in. I’m getting 12 volt power to the relay and to >> both sides of the fuse. > > There are two power sources at the glow plug relay - the big > wire going to the strip fuse and the trigger power for the > relay coil. What you describe suggests you only tested the > big wire - but it's not clear. > > There is wire red with a white stripe that is in the little > connector on top of the relay and connects to terminal 15 on > the relay. This should have power anytime the key is on. > It's power comes from fuse #15. > >> The odd thing is, when I test the glow plug posts on the >> relay with my analog tester it shows they each have voltage >> when grounding to the engine. This voltage is present at all >> times. > > Which post is this? The 5 terminals under the big connector > on top of the relay? The big one with a nut securing the > wire? I'm confused. > >> The weird part is that when I run a test wire from >> the glow plug relay posts to engine ground I get no >> reaction! No juice is flowing. Could there be a problem with >> the wire(s) that connect to the ignition circuit? > > I'm not sure what you have done - but here is the process I > would use. > > Using a voltmeter with one lead on ground, use the other lead > on the screw on the inboard (away from the fender) end of the > strip fuse. This is the "down stream" side of the fuse. If > there is 12 VDC here, then turn on the key and listen/feel for > the relay to click AND measure at the screw again. Expect to > see about 9 VDC on the screw. If there is more than about 10 > VDC, and/or the relay doesn't click, then the supply is okay, > but it's not connecting to the glow plugs. If there is less > than about 8 VDC I would suspect either the battery is bad or > the fuse has failed. > > If the relay did NOT click, next measure the voltage at the > terminal with the red wire at the small connector (contact > #15) This should have 12 VDC anytime the key is on. If not, > first check fuse #15. > > Then I would open the small connector and jumper from the > strip fuse screw to the red wire at terminal 15. You should > hear/feel the relay click. If not, the ground wire has a > problem or the relay is bad. > > Then I would use my glow plug tester rig that uses an old +-30 > amp ammeter to test each glow plug. > > If there is something I didn't explain well, let me know and > I'll have another go at it. > > > _______________________________________ > http://www.okiebenz.com > > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
