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Daniel Wilson
Daniel Wilson,
Category: Medium and Heavy Trucks
Satisfied Customers: 5560
Experience:  Owner at DJ Wilson
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What style plug is the connector for diagnostics on a 1992

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what style plug is the connector for diagnostics on a 1992 peterbilt with a detriot engine??. i believe ddec 2... its a rectangle plug not a round plug like newer trucks... i need to see what its called to see if Nexiq offers it for my USB-Link interface for hooking up with scanner.

Hi my name is***** will be glad to help. Bare with me while I pull those specs for you.

Click this link for the information requested.

DDEC2 connectors and adapters

Customer: replied 2 months ago.
ok thank you.
can i ask you an AC question on this same '92 Peterbilt, on this thread ?

Usually there is one question per thread as the site only does one credit for us per question but if it is something not too complicated lets give it a shot.

Bonuses are always greatly appreciated as well.

Customer: replied 2 months ago.
ok. when i cut the ac on, the engine fan comes on and stays on, even if i cut the ac off.... if i never cut the ac on the fan doesnt come on and stick, it functions correctly if i never cut the ac on. it only sticks on when i do use the ac. already replaced hi pressre switch

Is there a manual override switch in the cab?

Click this link for a diagram

Let me pull up some further info on the fan circuit

Customer: replied 2 months ago.
there is . it cuts the fan on manual or AUTO when the ac is off and has not been on.
when ac gets cut on, fan stays on and switch in cab does nothing

Is this a 379?

Customer: replied 2 months ago.

Try swapping out the relays in the panel and cleaning and inspecting all grounds. As well

Swap with a known good one from another location for test purposes

Daniel Wilson and other Medium and Heavy Trucks Specialists are ready to help you

I posted the link in the private contact window to copy and paste in your browser.

Customer: replied 2 months ago.
I don't see a fan relay at the driver side kick panel

If there is no relay it will be commanded to ground through the ECM

Customer: replied 2 months ago.
could it be faulty ECM?? when i disconnect hi pressure switch, fan goes off, when i jump it or plug it fan comes on. ... right now truck has been off for about 10 min, if i go to crank it with ac off, fan will immediately come on too..

Have you tested the high pressure switch to see if it is working with an ohm meter? Open and closed with the system cycling and verified the system has sufficient charge?

Customer: replied 2 months ago.
no, dont know how to test, sorry
Customer: replied 2 months ago.
it was doing this, with old switch, installed new one and still doing it

Understood. I have to head out on the road for a while but let me put my thoughts together some more on this and follow up later.