Please help. I have 1991 350sd with the "after 1989" glow plug relay. My question is ,could I replace it with the older style with the fuse?
The one I have is original.
Thanks,
Sausage

There are instructions online on how to do this.
(You may have to plunder around awhile to find them.)

It's basically just a great big relay with great big contactors that may be dirty or burned and you could get lucky and be able to clean them!

__________________
'84 300SD sold
124.128

Yes. Your 5-socket harness connector will likely plug into the 4-pin connector on a non-afterglow relay.

x2. They're very simple inside.

The afterglow relay for a 140 SD - e.g., '93 300SD - is oddly much cheaper than other afterglow relays from that place in AZ.

Sixto
83 300SD
98 E320 wagon

aftermarket huco

https://www.amazon.com/Mercedes-Benz-Diesel-Engine-Relay-Preglow/dp/B01D7MLSJO/ref=sr_1_fkmr1_3?ie=UTF8&qid=1491271368&sr=8-3-fkmr1&keywords=91+350+sd+glow+plug+relay

__________________
2011 e320 cdi (132,000) current
2005 Jeep CRD diesel--2.8L (138,000 miles) wrecked, insurance took
1993 Mercedes benz 300D 2.5 Turbo Frybrid powered. (336,000 miles) wrecked and sold as parts car
1990 Mercedes benz 300D 2.5 Turbo (170,000 miles) wrecked and sold as parts car

Check out my Frybrid Vegtable Oil Conversion at http://1990300dfrybridconversion.shutterfly.com/

Yes this will work. Yes, you'll lose afterglow. Yes, you'll lose the better preglow timer since the relay won't use the temp sensor in the head.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

That's an afterglow relay - note 5-pin small connector - with strip fuse. I had one on my '93 SD then transferred to my '87 300D with afterglow temp sender in place of BFS 50* switch and it afterglew.

Sixto
83 300SD
98 E320 wagon