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AD41B early tach questions

skiss

skiss

Regular Contributor
"When I replaced my dead tachs

"When I replaced my dead tachs 5 yrs ago when I bought the boat, I put in a 828601. It looked identical to the old 864022 except no hour meter.
Engine went to 2600 rpm and thats all. I had the 2 engines rebuilt and guess what rpm issue.
The shop put a mechanical / optical rev counter in the v cone on the crank front and we picked up 3500 rpm half throtle no load but in gear on land. The tach showed 1500. What should I do now? Both engines and tachs react and measure the same. Buy new tachs or is there something else? Both tachs are 12V.
Engines idle at 570 and my tach shows 220. Thank you in advance....."
 
"Sailor,
Your tachs gets the

"Sailor,
Your tachs gets the pulses from the alternator, it looks like the pulses it gets one third of what it should get.
I think you should investigate your alternators, to make sure they are original and have the correct V cones, and that the belts are tight and not slipping."
 
"Thank you Martin and Morten,

"Thank you Martin and Morten, before I get the alts rebuilt I need to know if the tach I am using is compatible. The belts are new and were the same as the old ones on the engine. I cannot speak to the pulley dia but suspect it is the original as the alts also LOOK original and also are charging according to the voltmeter (14V).
Can someone answer 3 questions...
1. Is 828601 (12v) compatible and correct?
The tach was a 864022, and the book lists 864023,858655,858087,838811 tachs. I do not know anything about the differences of the tachs.
2. If answer to #1 is no, then what part#s are compatible and is there a universal electronic tach that can be used? ( I read in an old post a suggestion that this is possible, but was for a diff model engine?)
3. If answer to #1 is yes, what part of the alternator should be inspected or replaced, assuming the pulley is the correct diameter on both engines?
The manual tach cone was in the centre of the crank so it should be accurate. We tried to use the photo strip, but the space was too tight to get the unit in and take a reading.
Thank you....."
 
"check this site,

[url=""]

"check this site,

www.marinepartseurope.com

it shows all the updated part numbers that are compatable for your old style tachos. if you want the new type universal tacho it is part no 873992
what is the max rpm you need?
as i have the new type available but only upto 3400rpm"
 
You may in theory use any tach

You may in theory use any tach that takes the pulses from the 'W' (AC) outlet of the alternator. However to get the setting right is another thing unless the tach is adjustable. You need a tach that goes to min 4200 rpm which is the 'high idle rev' on your engine.
 
"Thank you Scott. Max rpm is

"Thank you Scott. Max rpm is 3900 and cruise is supposed to be 3500 according to manual.
Question.... the universal tach is it electronic, meaning it is programmable?
The plug on the harness has only 4 male spades arranged on a square block plus a socket for the bulb. Can I get a universal and program it to my alternator pulse output? I asked the Penta dealer and he said the AD41B is not compatible with the new tachs because it does not have a computer, but I am wondering if your suggestion is a different animal.
Thank you"
 
"Thanks Morten....The tachs we

"Thanks Morten....The tachs were 5000 rpm. Still looking for a suggestion I can act on. The Penta dealer said he will call if he can locate a used working tach, but I am not holding my breath for this to happen, since I talked to him 2 months ago before and he could not help. If I order a new tach and it turns out to be something else thats wrong, then I am stuck with it. Thats why I am trying to figure this out before diving in.
Thank you"
 
"Do you by any chance have som

"Do you by any chance have some 'fancy' charge regulator installed?
I would have taken down one alternator and one tack,taken it to an electrical shop and tested.
Try to measure the dia on the crank pulley and alternator pulley, then calculate how many turns on the alternator equals one engine turn.
As an example: dia (crak shaft) x 3,14 = 50 cm
dia (altern) x 3,14 = 25 cm

Your alternator makes 2 turns to every engine rev."
 
"Thank you......that will inde

"Thank you......that will indeed tell me if something is not right. I have to wait for the wk-end to get to the boat to do the measurements. I was also thinking about taking one alt off and giving it to a rebuilder for analysis with the tach I have. The answer to the fancy question is no. Everything looks stock. I know the previous owner well, and still socialize with him, and was told there was no mods done such as alt upgrade etc. The boat did partially sink once (fresh water and at the dock and the dash never went under, just engines). The dealer and insurance took care of repairs, but I do notice some connections in the engine harness have the white and blue corrosion. They were sprayed with contact cleaner, dressed with dielectric grease and the plugs were repeatedly pressed together and taken apart to shine up the pins. No difference. Thank you"
 
"the connections on the new ta

"the connections on the new tachos are the same connector as the old ones, they are programmable and are compatable with your engine. see pic for ref of connector
290619.jpg
"
 
"I think I am on to something.

"I think I am on to something. The installed tachs pn828601 replaced by 858558 are for the AD40B engine. Does the 40B have a different Alt W pulse than my AD41B Alternators? Means new tachs if answer is Yes I presume, or is there any simple mod to the remedy the W pulse."
 
"I may be wrong, but I think t

"I may be wrong, but I think to remember that some of the 'old' Volvo tachs had a 'loop' at the back that had to be cut away to get them to show right. All the Volvos up to when they started using electronic may use the same tach, apart from the rpm range."
 
"No loop that I can see......m

"No loop that I can see......maybe add a loop somewhere? My thinking is going in the direction of new tachs. Scott.... thank you for the pic. My harness plug is the same as the 4 spade socket. Question... what is the fifth spade for beside the socket? My original broken tach had this but on the other side of the socket and was not used to my knowledge. My incorrect tach pn 828601 for a 40 engine does not have any spade beside the socket. PN873992 the programable tach looks like the way to go, but the info on the web says it replaces tachs with a existing digital display, and the AD41B is not listed as a applicable engine application? Any way to double check if it is a Volvo ovesight, or I have to stay with old style Volvo tachs? Thank you again for your patience with all my questions."
 
OOps.. looked again on the Eur

OOps.. looked again on the Europe site and engine is listed on page 2. Not in English so I hope I am reading it correctly. Thankyou.
 
"Looking at the el-schematic o

"Looking at the el-schematic of your engine, here:
http://vppneuapps.volvo.com/ww/PIE/ViewFileFrame.aspx?n=172294&r=2006-01-27-10-0 2-07&t=PDF&a=7746338&p=T403&d=Owners%20Publication&s=4229869&lang=sv-SE
I notice that one of the inputs to the tach seems to come from the charge light circuit (61) on the alternator. To me looks a bit strange, but must be for a reason. I remember having trouble with those tachs if installing Ladac regulators. Sure you do not have anything like that installed? Double check that you get all signals correct to your tachs, use a multimeter with Hz readings as well an the W output. Measure both at tach and alternator."
 
"hi, the terminal at the side

"hi, the terminal at the side is for the memory of the tacho, a linking cable comes with the new tachos to connect to the main positive on the back of the ignition switch a bit like the memory on a car radio, its so the tacho does not loose the settings that are programmed in, you can change the pulse settings by pushing a small screwdriver in the hole next to the terminal."
 
"the connection from the charg

"the connection from the charge light circuit 61 is just for the engine hours, its so you only regester hours when the engine is actually running and not just with the ignition left on."
 
"Thank you all....... I bought

"Thank you all....... I bought the new tach that reads up to 4600 rpm. Programmed it, and it works like a charm. These new tachs are really nice. They can be reprogrammed if need be. The code sheet shows just about every volvo diesel engine. Thank you again, hopefully others will get this new tach when they confront this problem."
 
"anyone wanting one of these u

"anyone wanting one of these universal tachometers, i have quite a few (all brand new with full instructions) £40 each. Please note i only have the 2600rpm & 3400rpm, so not suitable if your engine max rpm is above 3400rpm"
 
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