under dash tach wiring harness

[drturf0]

does any one know which wires do what . i. m tring to wire up a isspro tach on a buddies 92 , he didn't get the wiring harness with it . so i'm just going to hard wire it into the plug under the dash.

 

[BCook1]

Some tach info

Greetings,

I recently put the autometer tach in my 92. The factory tach harness in mine had four wires in a flat plug. The grey was the signal lead for the tach itself but I could not use it because it only provided one pulse per rev and that was not enough to get the tach within adjusting range. I had to use the magnetic pickup that came with the tach and is hoseclamped to the alt. Not as bad as it looks - stuck it through the clutch firewall boot. The dash light wire is easily found with a test light and by turning on and off the parking lights. The ignition source wire can be found in a similar manner with a test light. I would give you the color codes but mine were different from the manual. A chassis ground can be found anywhere. Use the "protected" (plastic covered) female solderless connectors when plugging into the harness - no crossover. It might be just as easy to get the harness adaptor.

 

["Mad Max"]

Fellas - I think there is some additional good info in a post on the 3rd page of threads titles tach by BYates. I think they went into the color codes, etc.

- S

 

[Tim1]

isspro tach

Hey bud, I put in the same tach, in addition to the wiring, you have to set the dip switches on the back of the tach for the cummins. I'll look for my instructions and post. Tim

 

[BushWakr - RIP]

Hey guys, I have a fellow who can use some help too... his situation is kinda weird...

He has a 91 with the intercooler, which makes us think it's a 91. 5+ right... .

Well he has an Isspro tach he's trying to put in and he has NO wiring harnes or sensor on the gear cover. How is it that he has what looks to be a factory IC but no tach harness/sensor???

If there is no harness/sensor would there still be the "lead and plug" at the cylinder head were the connector usually attachs????



Any help for this fella would be appreciated.



Pastor Bob.

 

[drturf0]

ok this isspro tach has 3 wires on it.

1-red wire which i know is for ign. hot.

1- white wire what do i hook this one up to

1- black wire don't know where this one goes either

i know that one of the wires either black or white goes to the gray wire under the dash, but which one the black or the white? then where does the other one go?

 

[Philip]

If that tach is like most the black is a ground wire. The white would be a signal wire. So the white would go to the grey wire in the factory plug.



BW does that truck have a stick in it. If it does Dodge might have got cheap and had two different harness's for our trucks. The rpm sensor was needed for OD. On the stick it wouldn't be needed.



There was another person in a earlyer post said that 91. 5's didn't come with rpm sensor and tach harness.

 

[dpuckett]

My 91. 5 that I had two years ago didnt have the factory pickup and wiring, either, so it must be a 92+ thing. I have the color codes listed somewhere from a guy at ISSPRO- have to look them up and post here. Gimme a minute.....

 

[dpuckett]

A direct quote from Scot Driscol at ISSPRO-

"There should be three wires from the rear of the tach,

"Black goes to ground then to the sensor,

"Red goes to 12 volt ignition source,

"White goes to the other sensor wire. "



Mine has a phantom green wire in the pigtail, but it doesnt go anywhere inside- it is cut off right where the other 3 wires go into the tach itself.



As for the under-dash wires on the truck end... . hafta do asome searching; I dont remember off the top of my head.



Daniel

 

[Tim1]

GET ORGANIZED

Boy, I hate it when I can't find something!!!! Still looking! Tim

 

[drturf0]

well worked on it tonite , hooked all the wires up , when i crank the truck the needle will jump up to about 7 or 800 RPM's then fall right back down to "0"

 

[HonkinDiesel]

Originally posted by drturf0

well worked on it tonite , hooked all the wires up , when i crank the truck the needle will jump up to about 7 or 800 RPM's then fall right back down to "0"

Well you are doing better than me... .

I just bought the Isspro 8503, I checked the manuals and read instructions and installed it today. The tach connector on my 93 is located right above my fuse panel. It is 4 pin straight side by side connector. Black in color. Anyway,

Tach red wire connected to ignition positive (black with red stripe)

Tach black to chassis or ground (black)

Tach white connected to Sensor (grey wire)

Tach lamp connected to dash light circuit (Orange)



I don't get any idle speed showing at all. The only time I move the indicator is if I really rev the engine. Something wierd here. Unless you guys have some pointers here, I'll be talkin to PDR on Monday.

 

[drturf0]

i talked to Piers yesterday and found out that you gotta have the sensor kit, it has some kind of filter in it . part # 8512-92. now thats for a 92 model

 

[BCook1]

Slow tach

The grey lead only gives one pulse per rev and that is not enough to run the tach. The magnetic pickup that hoseclamps to the alternater picks up between 4 and 6 pulses per rev because of the windings inside and that number of pulses is enough to get the tach within adjustment range. Inside the tach you will probably find a small knob that you can turn and fine tune the idle and WOT rpms. You may have to go to a diesel shop to get an accurate rpm reading so you can set the tach. I didn't bother and just set the idle at about 750. I checked the wot rpms and they were about 2900 so I knew I was close enough. The service manual gives the wot no load rpm range that these engines should have.

 

[drturf0]

BCook, yes that works with the autometer tachs, but the isspro 8503 tach has no adjustments , it is set up for 1 pulse per rev, for the diesels.

 

[michigandon]

I tried posting this in the last tachometer thread here and never got an answer. So, I'm going to try again...



I've got an Isspro tach mounted into my new dash that I fabbed for my coach. I have the '93 D250 engine wiring harness and ECM, but here's the kicker. I do NOT have any of the under dash wiring from the donor truck. I DO have the 50-prong firewall plug, and I see in the manual that one of these prongs is labled "tachometer output". Which wire on the tach goes to this plug, and where would the other three wires hook up to?



TIA!!!

Don

 

[HonkinDiesel]

Originally posted by drturf0

i talked to Piers yesterday and found out that you gotta have the sensor kit, it has some kind of filter in it . part # 8512-92. now thats for a 92 model

I talked to PDR as well today. Its a special wiring harness kit that filters the signal from the dash output, currently on back order. He thinks it is just a diode in the circuit of the sensor line (White wire).

Has anyone investigated this or know anything about it?

If it is just a lousy 0. 59 cent inline signal diode, I can insert one myself.

 

[cerberusiam]

michigandon, the signal wire on the tach is the one you would hook to tachometer output on the firewall plug. Depending on your tach it could be red or black. You will usually have four wires on a tach, the signal wire for measuring, a ground, a power wire, and a internal light wire. Use your tach instructions to make sure which wire is which. This thread and other ones indicate there are potential issues with the existing wiring. As near as I can tell the crank sensor was only needed on the trucks that had the charging system regulated by the PCM and the ones that came with a tack. Depending on year and options the wiring may or may not be in the block and/or PCM. You will just have to try it and see what happens. Good luck.

 

[Tim1]

Found it!!!! Tach #8585m Isspro tach microprocessor version. On the back is a cap to remove and set the calibration switches #2on and all others off. On is up. Wiring is Red-ign hot, black-ground, white-sensor source, green-dash lites,violet is a alternator tap or if the tach acts erratic, disconnect white and hook to violet, it has additional electrical niose filtering. Tach mounting pod,VDO 240-018. Hopes this helps! Tim

 

[benefits]

I cant see to find the plug that you guys are talking about. I have a 1991. 5 cummins and do not have the tach but i was wondering what wiring I would need to do and I would like to not have to put magnets on the flywheel if i dont have to. I was wondering if anyone had a picture of the plug that im supposed to use. I am wanting to buy an Isspro 2" gauge model #R8503. Unless I need a different one.