Before installing the inline 1 amp fuse later today I checked the current draw to see what it was measuring.Well the pump sounds fine and pulls 0.9 amps. Just like it is supposed to. (I used a 2 amp external battery charger).

I'm happy it is not frozen and I'll get a 1A fuse later today.

(Do I need a slow blow or a fast acting fuse. Sure hope Radio shack has what I need).

Then I wanted to do a test:

So with a cold car/engine; 32F out, and car battery installed , I got in car, with engine off to see if I could hear the pump run. I had key in position turned clockwise to position just before it cranks engine.

I pretty much selected all the buttons and fan speeds to see if the little auxiliary pump would start. It did not start up.

My question is this:

1.It there a temperature perameter that needs to be met for this pump to operate? Like the engine needs to warm up to a certain temperature. And if so where is this switch.

2. Does this pump run in any heat mode, ie dial in Red Zone.

I really don't know if this pump has operated in the past and I'm semi-tempted to just leave it disconnected as others have done. The heat has been great in the past. I sort of want to keep the car as original as possible and get things done to make the car safer and better. I'm at a cross road.

I Have read many links so far just need some assistance and advice. Thanks.

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1982 300SD

I can hear mine run when I pre-glow, so I think it should work when the car is cold and the key is on.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

I remember seeing a write up from years past, and it stated a slo-blo fuse. Glad to hear you are doing this mod, it will save a headache later.

__________________
DO IT RIGHT THE FIRST TIME, DON'T BE A HACK
Political Correctness is NOT part of my vocabulary
and finally FIGHT CRIME...SHOOT BACK

'82 240D Stick
'85 300D Auto
Drove my first MB at age 16 1960 300SL W190

Thank you. I'm done with it. Roy (Hunter) was nice to call me after I sent him an email yesterday about the fuse style. He stated that he has used both slow blow and quick blow fuses. Either is fine according to him. I have no idea what type fuse I put in other than it was a 1 amp. Just a glass outer cover and a fine wire in side. It wasn't paper coated so I'm thinking it is a fast blow. But I'm no expert on fuses. I tested it, hot wired, with a 2 amp battery charger and it ran fine; so fuse holds the load.

Start and stop a few times and no problems.

So I'm safe.

I asked him if I should fuse the MonoValve and he said no. He said the fuse in the fuse box will blow if the Mono Valve shorts or the coil wires themselves in the Monovalve will just fail and seperate as they are very fine like human hair. So I did not fuse the MonoValve.

He said failure of the Mono Valve will not take out the CCU, so I left it unfused.

I'm just trying to protect the CCU in event of any future pump seizure.

I'll quit while I'm ahead.

Thanks for reples.

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1982 300SD

I am using a fast blow 1 amp ATO "Blade Type Fuse". Motors generally need a slow blow fuse because there is a possibility of a call for a slight increase of amperage during start up. Then it will settle down. But I don't think this part warrants it. The CCUIII is delicate enough that any increase in amperage could cause havoc. So if the pump does need an extra umph to get started, then it should be replaced.

I believe the pump operates whenever heat is needed on any mode except for "economy". And this is dictated by the temperature in the cabin relating to the temperature setting on the wheel.

__________________
1983 123.133 California
- GreaseCar Veg System

If you find that the motor is running slower with the slo blow fuse, remember that slo blow fuses have more voltage drop than fast blow fuses. You may need to change to a 1.5A or 2A fast blow fuse.

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Ron Schroeder
'85 300 Turbo Diesel 2 tank WVO
'83 300 Turbo Diesel 2 tank WVO
Some former WVO vehicles since ~1980:
'83 Mercedes 240D
'80 Audi 4000D
'83 ISUZU Pup
'70 SAAB 99 with Kubota diesel
'76 Honda Civic with Kubota diesel
'86 Golf
Several diesel generators
All with 2 tank WVO conversion
LI NY

The pump is triggered by the temperature wheel. Any temperature requiring heat turns it on, even in the "economy" mode....all that mode does is disable the A/C compressor. You should be able to hear it running when glowing the engine....I can hear mine....

Might not be able to hear it quite as well on a 300D though because its further away in the engine compartment than it is on a W126.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Right. My bad on my previous comment.

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1983 123.133 California
- GreaseCar Veg System

Thanks for replies and information. Now I know what to expect as to when the pump should be running. All modes when set point is above cabin temperature. I'll see if mine runs when I'm Glowing.

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1982 300SD

The cold engine lockout doesn't disable the pump?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Anybody know if there is a Cold Engine Lock temp swit out as Kerry mentioned to disable the pump until engine gets warm or does the pump run even with a cold engine.

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1982 300SD