The blower motor for the heater comes on at initial startup and can be controlled by the CCU. Howerver it only runs for about 2 mins and then shuts off and will not come back on. The fuses are OK since the blower runs but is there another relay or something that can be bad I have missed.

I used the search function but did not see any posts with a similar problem. The wife is starting to get a little peeved about not having heat.....help!

Thanks,
Stephen

__________________
85 300D 305K miles WVO(105K so far), Mine
82 300SD 235K miles BIO-D, Wifes
96 F250 SC PSD 4X4 285K MILES BIO-D, Ours
89 BRONCO 182K MILES sold
Finally Compression Ignition Only!

Could be a CCU issue, there are many solder points that, over time fail, you'll have to pull the unit to check.

__________________
83 SD

84 CD

Someone is bound to provide a better answer than this, but if you look under the dash on the passenger side you will see the bottom of the blower. You will also see two boxes that look like large relays. They are on either side of the blower.

These boxes are some kind of controller for the fan and when one or both of them fails the fan will not operate. As I recall they cost quite a bit, so you might want to find some at a Pick-N-Pull and swap them out.

Hopefully someone can tell you just what these boxes are called and how to test them. It has been many years since I had to deal with this problem.

My brother in law said his was doing the same thing and the MB guy tested those "relays" near the blower motor one was out of speck, replaced and all was good.

I was hoping someone might know what they are called and what their tolerances are, my bro said they checked them with a Voltmeter.

Thanks,
Stephen

__________________
85 300D 305K miles WVO(105K so far), Mine
82 300SD 235K miles BIO-D, Wifes
96 F250 SC PSD 4X4 285K MILES BIO-D, Ours
89 BRONCO 182K MILES sold
Finally Compression Ignition Only!

You might pull the two boxes and take them to a dealer to be tested. I should imagine they would do this for free.

You could also find out what the proper name for them is and start looking for them on Ebay assuming yours check bad.

very good possibility that brushes could be bad on motor.. had that happen to my 85 300SD. you can replace brushes if you have tinkering ability

George Murphy over on MBUSA forum can help with brushes. might even have a rebuilt motor available. that's what i did, bought rebuilt from him.

__________________
R Martin
Dallas, TX (Addison)

86 560SEL, 128K

this might be what you are refering to? heater blower relay


http://www.allpartsexpress.com/ShopByVehicle.epc?q=1981-MERCEDES--BENZ-300sd--/--L5--3005cc--3.0l--Diesel--Fi--Turbo-Electrical&yearid=1981%40%401981&makeid=MERCEDES+BENZ%40%40MERCEDES+BENZ%40%40X&engineid=1194005%40%40300SD++%2F+L5%2D3005cc+3%2E0L+DIESEL+FI++Turbo%40%40300SD&catid=Electrical%40%40Electrical&subcatid=Heater+Control+Unit%2C+Rebuilt@@Heater+Control+Unit%2C+Rebuilt&mode=PA



Charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

hey, i just fixed my nonworking blower motor. at first, i didn't have power to the fan. i took out the glove box and pulled the connectors for the two relays to test for power. both had power, and when i reconnected the second relay back up, the fan kicked, and the fuse blew. replaced fuse, blew again. i then took out the fan and noticed my motor brushes were super short...about 1cm. took the fan to the bench and hooked it up to a battery. it worked, so i assumed that the short brushes were pulling too much amps. went to the hardware store [actually went to 3. the third was the only one with brushes] and bought 2 new brushes for 12 bucks total. got them big so i could sand them down to fit. took out the old ones, got the new ones to fit in the brushes slots with room for a spring, soldered them in using some flux paste to clean the old leads, and now i have a fully functional fan.

i should also mention i had resoldered all the contact points on the ccu. luckily, all my vacuum pods work.

now i have to figure out why my rear window defroster doesnt work. if anyone knows where the relays for it is, would appreciate the lead.

cheers

Thanks for all the input I will be digging into it this weekend. I'll post the results when finished.

For now the wife is using a 12V heater that plugs into the cig lighter= not happy

Thanks,
Stephen

__________________
85 300D 305K miles WVO(105K so far), Mine
82 300SD 235K miles BIO-D, Wifes
96 F250 SC PSD 4X4 285K MILES BIO-D, Ours
89 BRONCO 182K MILES sold
Finally Compression Ignition Only!

the dealer charges for a full electrical test on your car, but they don't test relays standalone. they will do the electrical test for $150 at my dealer. i think it's a precondition to all repairs or maintenance so if you're buying some other service, they will do it for free and then tell you everything that's wrong with your car electrically, in an attempt to sell you a service. you can refuse the service but keep a printout (and they keep it in their records) of the problems. for example, you can buy a new battery from them, and they will do the electrical test when they replace it.

__________________