'87 300 SDL, to buy a whole new time relay or not...
 

Hello all;

I've had, for the past couple of days, a lack of glow plug light on the dash. No glow plug light at all, not even after start and it's not to easy to start even at 100F temperature here today. After searching around here I found advice about running tests on the time relay; which I did. All the glow plugs check at 0.8 ohms resistance from the six prong plug to ground. However, glaring right at me was a broken 80 amp fuse (I assume this is the problem).

My question is: should I replace the entire time relay unit at ~$145 or so, or just the 80 amp fuse. I know where I can get the time relay, but not where to buy the fuse. Why would the fuse short? Does this indicate something fishy in the relay itself, or somewhere else?

Please advise, I would greatly appreciate it.

Thanks in advance,

Matt Jackson
1987 300 SDL, 207K miles
new tires just yesterday - Falken Ziex, feel great, very quiet, $188 delivered for all 4 www.nctires.com

If the fuse is bad, just replace the fuse. Sometimes the fuse will fail after 20 years of cycling on and off. You can probably get it from Fastlane. Certainly from the stealer.

On the other hand.....
 

...the fuse is there to protect the glow plug circuit. If it is blown there may be a reason why. Buy two fuses and if as Brian correctly suggests, this is just a case of an old (marginal) fuse failing then you have a cheap repair. If however it is an indicator of something else wrong, then you still have a spare. Could be a bad relay or a shorted Glow Plug.

about $2.00 from the stealer. I also have a couple of used Time Relays (4 cyl, 5 cyl, and 6 cyl applications), if your interested, I'll sell it to you for less than $145. On my 87 300D, the fuse blew because of old age, installed a new one and all is fine.

Start simple and cheap. There's plenty of time to make it complicated and expensive. (Do I hear applause from P.E.H? :D)

Dervman said it first, and I'll second the suggestion that you lay out $4 or $5 for two fuses, whether at the Dealer, or online.

Put one fuse in, see how long that lasts. If it holds, the old one died of old age. If the new fuse blows, there may be an overload or a short somewhere that you'll have to diagnose and repair.

Let us know if you need the second fuse.

Best regards,
Jim

JimH,

Clap, clap clap clap.

Would anyone replace the whole power panel in their house because of a blown fuse or tripped circuit breaker?

Peragro,

You said the fuse was broken. Does that mean it was not melted? If you had a short, the fuse would be melted. If just broken, its a fatigue failure.

Just replace the fuse. If there was a short in a GP, a new relay would not fix the problem.

P E H

Is the time relay the little black box in front of the ABS control unit and behind the AC dryer thing? On the drivers side?

Yes.

Sixto
95 S420
87 300SDL

Thanks I probably should get an extra one of those metal strips mine looks very old. Although I could always jump it if I need to get the car started, a nail or peice of wire would do it.

What does an 80-amp nail look like? :)

Sixto
95 S420
87 300SDL

Well if it's cold out it is better than getting it towed. :D It just controls the glowpulgs right? So I could just jump it start the car and remove it if I had to. I'll just get another one don't worry.

Sorry about the delay... I had to go out of town for the last few days, but it did give me the chance to go by the stealer. 4 fuses for under 5 bucks. I live about 3 hours from the nearest MB dealer. Everything seems to work fine, started up right away and worked fine.

Thanks for all the help, online and off.


Matt Jackson.

peragro,

You said you got new fuses but you didn't specify if you replaced the original fuse.

Did replaceing the fuse cure your problem?

P E H

yep, I replaced the 80 amp fuse and that cleared the problem up. Actually the car seems to be starting quicker now - maybe that's just my perception. I've got 3 spare fuses if I run into having to trouble shoot or get stranded.

Thanks for the help.